 1. Yes. `SaveChanges` uses transaction internally.
 2. Use `TransactionScope` to wrap multiple calls to `SaveChanges`

Example:

    using(var scope = new TransactionScope(TransactionScopeOption.Required,
        new TransactionOptions { IsolationLevel = IsolationLevel.ReadCommitted }))
    {
        // Do something 
        context.SaveChanges();
        // Do something else
        context.SaveChanges();
    
        scope.Complete();
    }

I am able to check out an entire `svn` repository using the following command: 

    svn co https://myaccount.svn.beanstalkapp.com/myapp/

But I cannot figure out the command to commit a single file. If I make to change to `myapp/page1.html`. 

How can I check in just that one file?

How can I commit a single file using SVN over a network?

Is there a way to select a DIV in the parent window using jQuery?

For example:

Main page contains this,

    &lt;div id=&quot;testdiv&quot;&gt;&lt;/div&gt;
Popup page has a form with some options and an &#39;Apply&#39; button. When the user clicks apply it affects the style attribute on the main page.

Something along the logic of,

    parent.$(&quot;#testdiv&quot;).attr(&quot;style&quot;, content from form);


jQuery select element in parent window

I would like know what is the best possible way to implement transactions with `DBContext`. In particular,

1. Does `DbContext.SaveChanges` implement transaction internall if i change multiple entities?
2. If i want to call `DbContext.SaveChanges` multiple times(same contxet/different contxets), how transaction can be achieved?

EF Code First DBContext and Transactions

<p>I would like know what is the best possible way to implement transactions with <code>DBContext</code>. In particular,</p>
<ol>
<li>Does <code>DbContext.SaveChanges</code> implement transaction internall if i change multiple entities?</li>
<li>If i want to call <code>DbContext.SaveChanges</code> multiple times(same contxet/different contxets), how transaction can be achieved?</li>
</ol>


Basically, I have a table which contains a few properties for a company. This is the &quot;master&quot; table and their ID is used in many other tables. I basically find their ID via this method:

    private Company currentcompany()
        {
            Company cuco = db.Companies.Single(x =&gt; x.username == User.Identity.Name);
            return cuco;
        }

I need to give users the ability to update various details about themselves stored in this table, which I did perfectly well - however, I noticed a big security hole!

Using Tamper Data on Firefox (And I imagine Fidler/many others), I could easily change the hidden ID and modify another companies details.

To stop this, I added the following lines to the modify action:

            Company cuco = currentcompany();
            
            if (company.id != cuco.id)
            {
                return Content(&quot;Security Error&quot;);
            }

(FYI - `Company` is a model/POCO representing a company, and `company` itself is the form data.)

After adding this, if I edit the ID in the form data, it works as expected and brings up &quot;Security Error&quot;, however, if there isn&#39;t an error and I go on, I get the error in the question.

&quot;An object with the same key already exists in the ObjectStateManager. The ObjectStateManager cannot track multiple objects with the same key.&quot;

I believe this is because EF is somehow detecting and keeping the first data pull, but I am just un sure on how to correct it.

Any advice?

edit-
--update--

If you can understand what I am trying to achieve, is there a better way of going around this?


An object with the same key already exists in the ObjectStateManager. The ObjectStateManager cannot track multiple objects with the same key

Given this extremely simple model:


    public class MyContext : BaseContext
    {
        public DbSet&lt;Foo&gt; Foos { get; set; }
        public DbSet&lt;Bar&gt; Bars { get; set; }
    }

    public class Foo
    {
        public int Id { get; set; }
        public int Data { get; set; }
        [Required]
        public virtual Bar Bar { get; set; }
    }

    public class Bar
    {
        public int Id { get; set; }
    }

The following program fails:


    object id;
    using (var context = new MyContext())
    {
        var foo = new Foo { Bar = new Bar() };
        context.Foos.Add(foo);
        context.SaveChanges();
        id = foo.Id;
    }
    using (var context = new MyContext())
    {
        var foo = context.Foos.Find(id);
        foo.Data = 2;
        context.SaveChanges(); //Crash here
    }

With a `DbEntityValidationException`. The message found in `EntityValidationErrors` is *The Bar field is required.*.

However, if I force loading of the `Bar` property by adding the following line before `SaveChanges`:

    var bar = foo.Bar;

Everything works fine. This also works if I remove the `[Required]` attribute.

Is this really the expected behavior? Are there any workarounds (besides loading every single required reference every time I want to update an entity)



EF: Validation failing on update when using lazy-loaded, required properties

Here is my model of 3 entities: Route, Location and LocationInRoute.   
![model][1]

the following method fails and get exception when commit it:

     public static Route InsertRouteIfNotExists(Guid companyId, IListLocation&gt; locations)
            {
                //Loop on locations and insert it without commit
                InsertLocations(companyId, routesOrLocations);
    
                RouteRepository routeRep = new RouteRepository();
                Route route = routeRep.FindRoute(companyId, locations);
                if (route == null)
                {
                    route = new Route()
                    {
                        CompanyId = companyId,
                        IsDeleted = false
                    };
                    routeRep.Insert(route);
                    LocationInRouteRepository locInRouteRep = new LocationInRouteRepository();
                    for (int i = 0; i &lt; locations.Count; i++)
                    {
                        locInRouteRep.Insert(new LocationInRoute()
                        {
                            //Id = i,
                            LocationId = locations[i].Id,
                            Order = i,
                            RouteId = route.Id
                        });
                    }
                }
                return route;
            }
When doing:

    InsertRouteIfNotExists(companyId, locations);
    UnitOfWork.Commit();
I got:

 &gt; Unable to determine the principal end of the &#39;SimTaskModel.FK_T_STF_SUB_LOCATION_IN_ROUTE_T_STF_LOCATION_location_id&#39; relationship. Multiple added entities may have the same primary key.

When splitting the commit and insert in into the methos - it works:
   

      public static Route InsertRouteIfNotExists(Guid companyId, IListLocation&gt; locations)
                {
                    //Loop on locations and insert it without commit
                    InsertLocations(companyId, routesOrLocations);
                    UnitOfWork.Commit();
        
                    RouteRepository routeRep = new RouteRepository();
                    Route route = routeRep.FindRoute(companyId, locations);
                    if (route == null)
                    {
                        route = new Route()
                        {
                            CompanyId = companyId,
                            IsDeleted = false
                        };
                        routeRep.Insert(route);
                        LocationInRouteRepository locInRouteRep = new LocationInRouteRepository();
                        for (int i = 0; i &lt; locations.Count; i++)
                        {
                            locInRouteRep.Insert(new LocationInRoute()
                            {
                                //Id = i,
                                LocationId = locations[i].Id,
                                Order = i,
                                RouteId = route.Id
                            });
                        }
                        UnitOfWork.Commit();
                    }
                    return route;
                }

I would like to call commit once and outside the method. Why it fails in the first example and what does this exception means?

  [1]: http://i.stack.imgur.com/tkPtR.jpg

Multiple added entities may have the same primary key

I&#39;m using the DbContext and Code First APIs introduced with Entity Framework 4.1.

The **data model** uses basic data types such as `string` and `DateTime`. The only data annotation I&#39;m using in some cases is `[Required]`, but that&#39;s not on any of the `DateTime` properties. Example:

	public virtual DateTime Start { get; set; }

The **DbContext subclass** is also simple and looks like:

	public class EventsContext : DbContext
	{
		public DbSet&lt;Event&gt; Events { get; set; }

		protected override void OnModelCreating(DbModelBuilder modelBuilder)
		{
			modelBuilder.Entity&lt;Event&gt;().ToTable(&quot;Events&quot;);
		}
	}

The **initializer** sets dates in the model to sensible values in either this year or next year.

However when I run the initializer, I get this error at `context.SaveChanges()`:

&gt; The conversion of a datetime2 data
&gt; type to a datetime data type resulted
&gt; in an out-of-range value. The
&gt; statement has been terminated.

I don&#39;t understand why this is happening at all because everything is so simple. I&#39;m also not sure how to fix it since there is no edmx file to edit.

Any ideas?

How to fix the datetime2 out-of-range conversion error using DbContext and SetInitializer?

I have this query and I get the error in this function:

    var accounts = from account in context.Accounts
                   from guranteer in account.Gurantors
                   select new AccountsReport
                   {
                       CreditRegistryId = account.CreditRegistryId,
                       AccountNumber = account.AccountNo,
                       DateOpened = account.DateOpened,
                   };
    
     return accounts.AsEnumerable()
                    .Select((account, index) =&gt; new AccountsReport()
                        {
                            RecordNumber = FormattedRowNumber(account, index + 1),
                            CreditRegistryId = account.CreditRegistryId,
                            DateLastUpdated = DateLastUpdated(account.CreditRegistryId, account.AccountNumber),
                            AccountNumber = FormattedAccountNumber(account.AccountType, account.AccountNumber)
                        })
                    .OrderBy(c=&gt;c.FormattedRecordNumber)
                    .ThenByDescending(c =&gt; c.StateChangeDate);


    public DateTime DateLastUpdated(long creditorRegistryId, string accountNo)
    {
        return (from h in context.AccountHistory
                where h.CreditorRegistryId == creditorRegistryId &amp;&amp; h.AccountNo == accountNo
                select h.LastUpdated).Max();
    }

Error is:

&gt;There is already an open DataReader associated with this Command which must be closed first. 

**Update:**

stack trace added:

    InvalidOperationException: There is already an open DataReader associated with this Command which must be closed first.]
       System.Data.SqlClient.SqlInternalConnectionTds.ValidateConnectionForExecute(SqlCommand command) +5008639
       System.Data.SqlClient.SqlConnection.ValidateConnectionForExecute(String method, SqlCommand command) +23
       System.Data.SqlClient.SqlCommand.ValidateCommand(String method, Boolean async) +144
       System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method, DbAsyncResult result) +87
       System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method) +32
       System.Data.SqlClient.SqlCommand.ExecuteReader(CommandBehavior behavior, String method) +141
       System.Data.SqlClient.SqlCommand.ExecuteDbDataReader(CommandBehavior behavior) +12
       System.Data.Common.DbCommand.ExecuteReader(CommandBehavior behavior) +10
       System.Data.EntityClient.EntityCommandDefinition.ExecuteStoreCommands(EntityCommand entityCommand, CommandBehavior behavior) +443
    
    [EntityCommandExecutionException: An error occurred while executing the command definition. See the inner exception for details.]
       System.Data.EntityClient.EntityCommandDefinition.ExecuteStoreCommands(EntityCommand entityCommand, CommandBehavior behavior) +479
       System.Data.Objects.Internal.ObjectQueryExecutionPlan.Execute(ObjectContext context, ObjectParameterCollection parameterValues) +683
       System.Data.Objects.ObjectQuery`1.GetResults(Nullable`1 forMergeOption) +119
       System.Data.Objects.ObjectQuery`1.System.Collections.Generic.IEnumerable&lt;T&gt;.GetEnumerator() +38
       System.Linq.Enumerable.Single(IEnumerable`1 source) +114
       System.Data.Objects.ELinq.ObjectQueryProvider.&lt;GetElementFunction&gt;b__3(IEnumerable`1 sequence) +4
       System.Data.Objects.ELinq.ObjectQueryProvider.ExecuteSingle(IEnumerable`1 query, Expression queryRoot) +29
       System.Data.Objects.ELinq.ObjectQueryProvider.System.Linq.IQueryProvider.Execute(Expression expression) +91
       System.Data.Entity.Internal.Linq.DbQueryProvider.Execute(Expression expression) +69
       System.Linq.Queryable.Max(IQueryable`1 source) +216
       CreditRegistry.Repositories.CreditRegistryRepository.DateLastUpdated(Int64 creditorRegistryId, String accountNo) in D:\Freelance Work\SuperExpert\CreditRegistry\CreditRegistry\Repositories\CreditRegistryRepository.cs:1497
       CreditRegistry.Repositories.CreditRegistryRepository.&lt;AccountDetails&gt;b__88(AccountsReport account, Int32 index) in D:\Freelance Work\SuperExpert\CreditRegistry\CreditRegistry\Repositories\CreditRegistryRepository.cs:1250
       System.Linq.&lt;SelectIterator&gt;d__7`2.MoveNext() +198
       System.Linq.Buffer`1..ctor(IEnumerable`1 source) +217
       System.Linq.&lt;GetEnumerator&gt;d__0.MoveNext() +96



There is already an open DataReader associated with this Command which must be closed first

I know there are similar questions here but they are either [telling me][1] to switch back to regular RDBMS systems if I need transactions or use [atomic operations][2] or [two-phase commit][3]. The second solution seems the best choice. The third I don&#39;t wish to follow because it seems that many things could go wrong and I can&#39;t test it in every aspect. I&#39;m having a hard time refactoring my project to perform atomic operations. I don&#39;t know whether this comes from my limited viewpoint (I have only worked with SQL databases so far), or whether it actually can&#39;t be done.

We would like to pilot test MongoDB at our company. We have chosen a relatively simple project - an SMS gateway. It allows our software to send SMS messages to the cellular network and the gateway does the dirty work: actually communicating with the providers via different communication protocols. The gateway also manages the billing of the messages. Every customer who applies for the service has to buy some credits. The system automatically decreases the user&#39;s balance when a message is sent and denies the access if the balance is insufficient. Also because we are customers of third party SMS providers, we may also have our own balances with them. We have to keep track of those as well.

I started thinking about how I can store the required data with MongoDB if I cut down some complexity (external billing, queued SMS sending). Coming from the SQL world, I would create a separate table for users, another one for SMS messages, and one for storing the transactions regarding the users&#39; balance. Let&#39;s say I create separate collections for all of those in MongoDB.

Imagine an SMS sending task with the following steps in this simplified system:

 1. check if the user has sufficient balance; deny access if there&#39;s not enough credit

 2. send and store the message in the SMS collection with the details and cost (in the live system the message would have a `status` attribute and a task would pick up it for delivery and set the price of the SMS according to its current state)

 3. decrease the users&#39;s balance by the cost of the sent message

 4. log the transaction in the transaction collection

Now what&#39;s the problem with that? MongoDB can do atomic updates only on one document. In the previous flow it could happen that some kind of error creeps in and the message gets stored in the database but the user&#39;s balance is not updated and/or the transaction is not logged.

I came up with two ideas:

- Create a single collection for the users, and store the balance as a field, user related transactions and messages as sub documents in the user&#39;s document. Because we can update documents atomically, this actually solves the transaction problem. Disadvantages: if the user sends many SMS messages, the size of the document could become large and the 4MB document limit could be reached. Maybe I can create history documents in such scenarios, but I don&#39;t think this would be a good idea. Also I don&#39;t know how fast the system would be if I  push more and more data to the same big document.

- Create one collection for users, and one for transactions. There can be two kinds of transactions: *credit purchase* with positive balance change and *messages sent* with negative balance change. Transaction may have a subdocument; for example in *messages sent* the details of the SMS can be embedded in the transaction. Disadvantages: I don&#39;t store the current user balance so I have to calculate it every time a user tries to send a message to tell if the message could go through or not. I&#39;m afraid this calculation can became slow as the number of stored transactions grows.

I&#39;m a little bit confused about which method to pick. Are there other solutions? I couldn&#39;t find any best practices online about how to work around these kinds of problems. I guess many programmers who are trying to become familiar with the NoSQL world are facing similar problems in the beginning.

  [1]: https://stackoverflow.com/questions/2655251/mongodb-transactions
  [2]: http://docs.mongodb.org/manual/tutorial/isolate-sequence-of-operations/
  [3]: http://docs.mongodb.org/manual/tutorial/perform-two-phase-commits/

How to work around the lack of transactions in MongoDB?

I have an observer and I register an `after_commit` callback.
How can I tell  whether it was fired after create or update?
I can tell an item was destroyed by asking `item.destroyed?` but `#new_record?` doesn&#39;t work since the item was saved.

I was going to solve it by adding `after_create`/`after_update` and do something like `@action = :create` inside and check the `@action` at `after_commit`, but it seems that the observer instance is a singleton and I might just override a value before it gets to the `after_commit`. So I solved it in an uglier way, storing the action in a map based on the item.id on after_create/update and checking its value on after_commit. Really ugly.

Is there any other way?

# Update

As @tardate said, `transaction_include_action?` is a good indication, though it&#39;s a private method, and in an observer it should be accessed with `#send`.

    class ProductScoreObserver &lt; ActiveRecord::Observer
      observe :product

      def after_commit(product)
        if product.send(:transaction_include_action?, :destroy)
          ...

Unfortunately, the `:on` option does not work in observers.

Just make sure you test the hell of your observers (look for `test_after_commit` gem if you use use_transactional_fixtures) so when you upgrade to new Rails version you&#39;ll know if it still works.

(Tested on 3.2.9)

# Update 2

Instead of Observers I now use ActiveSupport::Concern and `after_commit :blah, on: :create` works there.

Rails 3: How to identify after_commit action in observers? (create/update/destroy)

I&#39;m using CHASE bank. (Also Bank of America)
and I want to get my bank transactions and my balance if I can.
Is there an API for that? in PHP or JAVA?
If so, please let me know how to get them.




Is there an API to get bank transaction and bank balance?

I have created a database. I want to do the Transaction. `SaveCustomer()` contains more than one statement to insert records into `Customer, CustomerControl, Profile, Payment` table at that time.

When a user calls  `SaveCustomer()` method then that data will go to these 4 tables.so How can I do the transaction? If one table inserts failed then need to roll back everything. For example, when 3rd table inserts the record I got an error, then need to roll back previous two table&#39;s insert records also.

See my code:

    public void saveCustomer(){
        DBAdapter dbAdapter = DBAdapter.getDBAdapterInstance(RetailerOrderKeyActivity.this);
        dbAdapter.openDataBase();
        ContentValues initialValues = new ContentValues();
  		initialValues.put(&quot;CustomerName&quot;,customer.getName());
  		initialValues.put(&quot;Address&quot;,customer.getAddress());
  		initialValues.put(&quot;CustomerPID&quot;,strPID);
  		initialValues.put(&quot;Date&quot;,strDateOnly);
        long n = dbAdapter.insertRecordsInDB(&quot;Customer&quot;, null, initialValues);
            
    }
Likewise  other statement also there.

DBAdpter code is :

    public long insertRecordsInDB(String tableName, String nullColumnHack,ContentValues initialValues) {
		long n =-1;
		try {
			myDataBase.beginTransaction();
			n = myDataBase.insert(tableName, nullColumnHack, initialValues);
			
			myDataBase.endTransaction();
			myDataBase.setTransactionSuccessful();
		} catch (Exception e) {
			// how to do the rollback 
			e.printStackTrace();
		}
		
		return n;
	}



This is the full code:

      

    public class DBAdapter extends SQLiteOpenHelper {
    
    	private static String DB_PATH = &quot;/data/data/com.my.controller/databases/&quot;;
    	private static final String DB_NAME = &quot;customer&quot;;
    	private SQLiteDatabase myDataBase;
    	private final Context myContext;
    	private static DBAdapter mDBConnection;
    
    	
    	private DBAdapter(Context context) {
    		super(context, DB_NAME, null, 1);
    		this.myContext = context;
    		DB_PATH = &quot;/data/data/&quot;
    				+ context.getApplicationContext().getPackageName()
    				+ &quot;/databases/&quot;;
    		// The Android&#39;s default system path of your application database is
    		// &quot;/data/data/mypackagename/databases/&quot;
    	}
    	
    	
    	public static synchronized DBAdapter getDBAdapterInstance(Context context) {
    		if (mDBConnection == null) {
    			mDBConnection = new DBAdapter(context);
    		}
    		return mDBConnection;
    	}
    
    	
    	public void createDataBase() throws IOException {
    		boolean dbExist = checkDataBase();
    		if (dbExist) {
    			// do nothing - database already exist
    		} else {
    			// By calling following method 
    			// 1) an empty database will be created into the default system path of your application 
    			// 2) than we overwrite that database with our database.
    			this.getReadableDatabase();
    			try {
    				copyDataBase();
    			} catch (IOException e) {
    				throw new Error(&quot;Error copying database&quot;);
    			}
    		}
    	}
    
    	
    	private boolean checkDataBase() {
    		SQLiteDatabase checkDB = null;
    		
    		try {
    			String myPath = DB_PATH + DB_NAME;
    			checkDB = SQLiteDatabase.openDatabase(myPath, null,SQLiteDatabase.OPEN_READONLY);
    
    		} catch (SQLiteException e) {
    			// database does&#39;t exist yet.
    		}
    		if (checkDB != null) {
    			checkDB.close();
    		}
    		return checkDB != null ? true : false;
    	}
    
    	
    	private void copyDataBase() throws IOException {
    		InputStream myInput = myContext.getAssets().open(DB_NAME);
    		String outFileName = DB_PATH + DB_NAME;
    		OutputStream myOutput = new FileOutputStream(outFileName);  
  		byte[] buffer = new byte[1024];
    		int length;
    		while ((length = myInput.read(buffer)) &gt; 0) {
    			myOutput.write(buffer, 0, length);
    		}
    		    // Close the streams
    		myOutput.flush();
    		myOutput.close();
    		myInput.close();
    	}
     
    	/**
    	 * Open the database
    	 * @throws SQLException
    	 */
    	public void openDataBase() throws SQLException {
    		String myPath = DB_PATH + DB_NAME;
    		myDataBase = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READWRITE);		
    	}
    
    	
    	@Override
    	public synchronized void close() {
    		if (myDataBase != null)
    			myDataBase.close();
    		super.close();
    	}
    
    	/**
    	 * Call on creating data base for example for creating tables at run time
    	 */
    	@Override
    	public void onCreate(SQLiteDatabase db) {
    	}
    
    	
    	@Override
    	public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    		db.execSQL(&quot;ALTER TABLE WMPalmUploadControl ADD Testing int&quot;);
    		
    	}
    
    	public void upgradeDb(){
    		onUpgrade(myDataBase, 1, 2);
    	}
    	
    	public Cursor selectRecordsFromDB(String tableName, String[] tableColumns,
    			String whereClase, String whereArgs[], String groupBy,
    			String having, String orderBy) {
    		return myDataBase.query(tableName, tableColumns, whereClase, whereArgs,
    				groupBy, having, orderBy);
    	}
    	
    	
    	public ArrayList&lt;ArrayList&lt;String&gt;&gt; selectRecordsFromDBList(String tableName, String[] tableColumns,
    			String whereClase, String whereArgs[], String groupBy,
    			String having, String orderBy) {		
    		
    		ArrayList&lt;ArrayList&lt;String&gt;&gt; retList = new ArrayList&lt;ArrayList&lt;String&gt;&gt;();
    	      ArrayList&lt;String&gt; list = new ArrayList&lt;String&gt;();
    	      Cursor cursor = myDataBase.query(tableName, tableColumns, whereClase, whereArgs,
    					groupBy, having, orderBy);        
    	      if (cursor.moveToFirst()) {
    	         do {
    	        	 list = new ArrayList&lt;String&gt;();
    	        	 for(int i=0; i&lt;cursor.getColumnCount(); i++){	        		 
    	        		 list.add( cursor.getString(i) );
    	        	 }	 
    	        	 retList.add(list);
    	         } while (cursor.moveToNext());
    	      }
    	      if (cursor != null &amp;&amp; !cursor.isClosed()) {
    	         cursor.close();
    	      }
    	      return retList;
    
    	}	
    
    	
    	public long insertRecordsInDB(String tableName, String nullColumnHack,ContentValues initialValues) {
    		long n =-1;
    		try {
    			myDataBase.beginTransaction();
    			n = myDataBase.insert(tableName, nullColumnHack, initialValues);
    			
    			myDataBase.endTransaction();
    			myDataBase.setTransactionSuccessful();
    		} catch (Exception e) {
    			// how to do the rollback 
    			e.printStackTrace();
    		}
    		
    		return n;
    	}
    
    	
    	public boolean updateRecordInDB(String tableName,
    			ContentValues initialValues, String whereClause, String whereArgs[]) {
    		return myDataBase.update(tableName, initialValues, whereClause,
    				whereArgs) &gt; 0;				
    	}
    	
    	public int updateRecordsInDB(String tableName,
    			ContentValues initialValues, String whereClause, String whereArgs[]) {
    		return myDataBase.update(tableName, initialValues, whereClause, whereArgs);		
    	}
    
    
    	public int deleteRecordInDB(String tableName, String whereClause,
    			String[] whereArgs) {
    		return myDataBase.delete(tableName, whereClause, whereArgs);
    	}
    
    	
    	public Cursor selectRecordsFromDB(String query, String[] selectionArgs) {
    		return myDataBase.rawQuery(query, selectionArgs);		
    	}
    	
    	
    	public ArrayList&lt;ArrayList&lt;String&gt;&gt; selectRecordsFromDBList(String query, String[] selectionArgs) {	      
    	      ArrayList&lt;ArrayList&lt;String&gt;&gt; retList = new ArrayList&lt;ArrayList&lt;String&gt;&gt;();
    	      ArrayList&lt;String&gt; list = new ArrayList&lt;String&gt;();
    	      Cursor cursor = myDataBase.rawQuery(query, selectionArgs);	        
    	      if (cursor.moveToFirst()) {
    	         do {
    	        	 list = new ArrayList&lt;String&gt;();
    	        	 for(int i=0; i&lt;cursor.getColumnCount(); i++){	        		 
    	        		 list.add( cursor.getString(i) );
    	        	 }	 
    	        	 retList.add(list);
    	         } while (cursor.moveToNext());
    	      }
    	      if (cursor != null &amp;&amp; !cursor.isClosed()) {
    	         cursor.close();
    	      }
    	      return retList;
    	   }
    
    }
https://stackoverflow.com/questions/6951506/database-lock-problem-in-htc-desire/6955195#6955195.


I want to roll back if there any issues occurred when inserting the table data.


Please help me

Thanks.

I looked this same related question : 

Android Database Transaction

As demonstrated by previous Stack Overflow questions ([https://stackoverflow.com/questions/2425550/transactionscope-and-connection-pooling][1] and [https://stackoverflow.com/questions/3759897/how-does-sqlconnection-manage-isolationlevel][2]), the transaction isolation level leaks across pooled connections with SQL Server and ADO.NET (also System.Transactions and EF, because they build on top of ADO.NET).

This means, that the following dangerous sequence of events can happen in any application:

 1. A request happens which requires an explicit transaction to ensure data consistency
 2. Any other request comes in which does not use an explicit transaction because it is only doing uncritical reads. This request will now execute as serializable, **potentially causing dangerous blocking and deadlocks**

The question: **What is the best way to prevent this scenario?** Is it really required to use explicit transactions everywhere now?

Here is a self-contained repro. You will see that the third query will have inherited the Serializable level from the second query.

    class Program
    {
        static void Main(string[] args)
        {
            RunTest(null);
            RunTest(IsolationLevel.Serializable);
            RunTest(null);
            Console.ReadKey();
        }

        static void RunTest(IsolationLevel? isolationLevel)
        {
            using (var tran = isolationLevel == null ? null : new TransactionScope(0, new TransactionOptions() { IsolationLevel = isolationLevel.Value }))
            using (var conn = new SqlConnection(&quot;Data Source=(local); Integrated Security=true; Initial Catalog=master;&quot;))
            {
                conn.Open();

                var cmd = new SqlCommand(@&quot;
    select         
            case transaction_isolation_level 
                WHEN 0 THEN &#39;Unspecified&#39; 
                WHEN 1 THEN &#39;ReadUncommitted&#39; 
                WHEN 2 THEN &#39;ReadCommitted&#39; 
                WHEN 3 THEN &#39;RepeatableRead&#39; 
                WHEN 4 THEN &#39;Serializable&#39; 
                WHEN 5 THEN &#39;Snapshot&#39; 
            end as lvl, @@SPID
         from sys.dm_exec_sessions 
        where session_id = @@SPID&quot;, conn);

                using (var reader = cmd.ExecuteReader())
                {
                    while (reader.Read())
                    {
                        Console.WriteLine(&quot;Isolation Level = &quot; + reader.GetValue(0) + &quot;, SPID = &quot; + reader.GetValue(1));
                    }
                }

                if (tran != null) tran.Complete();
            }
        }
    }

Output:

    Isolation Level = ReadCommitted, SPID = 51
    Isolation Level = Serializable, SPID = 51
    Isolation Level = Serializable, SPID = 51 //leaked!


  [1]: https://stackoverflow.com/questions/2425550/transactionscope-and-connection-pooling
  [2]: https://stackoverflow.com/questions/3759897/how-does-sqlconnection-manage-isolationlevel

SQL Server: Isolation level leaks across pooled connections

I was wondering if the `DbContext` class is thread safe, I am assuming it&#39;s not, as I am currently executing paralell threads that access the `DbContext` in my application and I am getting a host of locking exceptions and other things that look like they may be thread related.

Until recently I wasn&#39;t getting any errors...but until recently I wasn&#39;t accessing the `DbContext` in the threads.

If I am right, what would people suggest as a solution?

Is DbContext thread safe?

Apologies if this has already been answered, but how do you guarantee one Entity Framework DbContext per request if you are not using an IOC container? (The answers I&#39;ve come across so far deal with IOC container solutions.)

It seems like most solutions hook into the `HttpContext.Current.Items` dictionary, but how do you guarantee disposal of the DbContext when the request is finished? (Or is disposal not absolutely necessary with an EF `DbContext`?)

**Edit**

I&#39;m currently instantiating and disposing my DbContext in my controllers, but I also have several separate instantiations of my DbContext in ActionFilters and my MembershipProvider (and I just noticed, also a couple validators). So, I thought it might be a good idea to centralize instantiation and storage of my DbContext to reduce overhead.

One DbContext per request in ASP.NET MVC (without IOC container)

I&#39;ve researched some information about techniques I could use to **unit test a DbContext**. I would like to add some **in-memory data** to the context so that my tests could run against it. I&#39;m using Database-First approach.

The two articles I&#39;ve found most usefull were [this][1] and [this][2].
That approach relies on creating an IContext interface that both MyContext and FakeContext will implement, allowing to Mock the context.

However, I&#39;m trying to avoid using repositories to abstract EF, as [pointed][3] [by][4] [some][5] people, since EF 4.1 already implements repository and unit of work patterns through DbSet and DbContext, and I really would like to preserve all the features implemented by the EF Team without having to maintain them myself with a generic repository, as I already did in other project (and it was kind of painful).

Working with an IContext will lead me to the same path (or won&#39;t it?).

I thought about **creating a FakeContext that inherits from main MyContext** and thus take advantage of the DbContext underneath it to run my tests without hitting the database.
I couldn&#39;t find similar implementations, so I&#39;m hoping someone can help me on this.

**Am I doing something wrong, or could this lead me to some problems that I&#39;m not anticipating?**


  [1]: http://romiller.com/2010/09/07/ef-ctp4-tips-tricks-testing-with-fake-dbcontext/
  [2]: http://refactorthis.wordpress.com/2011/05/31/mock-faking-dbcontext-in-entity-framework-4-1-with-a-generic-repository/
  [3]: http://jamesmckay.net/2011/03/abstracting-your-orm-is-a-futile-exercise/
  [4]: https://stackoverflow.com/questions/5488313/organizationally-where-should-i-put-common-queries-when-using-entity-framework-c/5488947#5488947
  [5]: https://stackoverflow.com/questions/5625746/generic-repository-with-ef-4-1-what-is-the-point

Unit Testing DbContext

Having this simple code I get &quot;Cannot drop database &quot;test_db&quot; because it is currently in use&quot; (CleanUp method) as I run it. 

    [TestFixture]
    public class ClientRepositoryTest
    {
		private const string CONNECTION_STRING = &quot;Data Source=.;Initial Catalog=test_db;Trusted_Connection=True&quot;;
		private DataContext _dataCntx;

		[SetUp]
		public void Init()
		{
			Database.SetInitializer(new DropCreateDatabaseAlways&lt;DataContext&gt;());
			_dataCntx = new DataContext(CONNECTION_STRING);
			_dataCntx.Database.Initialize(true);
		}

		[TearDown]
		public void CleanUp()
		{
			_dataCntx.Dispose();
			Database.Delete(CONNECTION_STRING);
		}
	}


DataContext has one property like this 

     public DbSet&lt;Client&gt; Clients { get; set; }


How can force my code to remove database?
Thanks

&quot;Cannot drop database because it is currently in use&quot;. How to fix?

I&#39;m using `System.ComponentModel.DataAnnotations` to provide validation for my Entity Framework 4.1 project.

For example:
    
    public class Player
    {
        [Required]
        [MaxLength(30)]
        [Display(Name = &quot;Player Name&quot;)]
        public string PlayerName { get; set; }

        [MaxLength(100)]
        [Display(Name = &quot;Player Description&quot;)]
        public string PlayerDescription{ get; set; }
    }

I need to retrieve the `Display.Name` annotation value to show it in a message such as *The chosen &quot;Player Name&quot; is Frank.*

=================================================================================

Another example of why I could need to retrieve annotations:

    var playerNameTextBox = new TextBox();
    playerNameTextBox.MaxLength = GetAnnotation(myPlayer.PlayerName, MaxLength);

How can I do that?

How to retrieve Data Annotations from code? (programmatically)

I am looking a way to set CommandTimeout for DbContext. After searching I found the way by casting DbContext into ObjectContext and setting value for CommandTimeout property of objectContext.

    var objectContext = (this.DbContext as IObjectContextAdapter).ObjectContext;

 But I have to work with DbContext.

How to set CommandTimeout for DbContext?

I have been reading a lot of articles explaining how to set up Entity Framework&#39;s `DbContext` so that only one is created and used per HTTP web request using various DI frameworks.

Why is this a good idea in the first place? What advantages do you gain by using this approach? Are there certain situations where this would be a good idea? Are there things that you can do using this technique that you can&#39;t do when instantiating `DbContext`s per repository method call?



One DbContext per web request... why?

My impression to date has been that a `DbContext` is meant to represent your database, and thus, if your application uses one database, you&#39;d want only one `DbContext`.

However, some colleagues want to break functional areas out into separate `DbContext` classes.

I believe this comes from a good place -- a desire to keep the code cleaner -- but it seems volatile. My gut&#39;s telling me it&#39;s a bad idea, but unfortunately, my gut feeling is not a sufficient condition for a design decision.

So I&#39;m looking for:

A) concrete examples of why this might be a bad idea;

B) assurances that this will all work out just fine.

Entity Framework: One Database, Multiple DbContexts. Is this a bad idea?

I am using Entity Framework 5 (`DBContext`) and I am trying to find the best way to deep copy an entity (i.e. copy the entity and all related objects) and then save the new entities in the database. How can I do this? I have looked into using extension methods such as `CloneHelper` but I am not sure if it applies to `DBContext`.

Content Type	Original Author	Original Content on Stackoverflow
Question	user396491	View Question on Stackoverflow
Solution 1 - Entity Framework	Ladislav Mrnka	View Answer on Stackoverflow

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