Both mappings will create exactly the same database schema with a non-nullable foreign key `SomethingId` and a referential constraint between the two related tables.

The first mapping with `MapKey` is used when you don&#39;t want to have the foreign key as a property in your model class. The type of association in this case is called *Independent Association*. You would apply the second mapping with `HasForeignKey` when the foreign key is a property in the model. This type is called *Foreign Key Association*.

In many scenarios it is easier to work with Foreign Key Associations, but many people consider it as less clean to have a relational artifact (a foreign key) in the object world and prefer Independent Associations therefore.

Here are some references about the two types of associations and their Pros and Cons:

- http://www.ladislavmrnka.com/2011/05/foreign-key-vs-independent-associations-in-ef-4/
- https://stackoverflow.com/questions/12606948/what-are-independent-associations-and-foreign-key-associations
- https://stackoverflow.com/questions/5281974/code-first-independent-associations-vs-foreign-key-associations



I have just installed Meteor version 0.5.9 (45fef52095) to my CentOS release 6.3 (Final) server (Linux version 2.6.32-279.19.1.el6.i686 (mockbuild@c6b8.bsys.dev.centos.org) (gcc version 4.4.6 20120305 (Red Hat 4.4.6-4) (GCC) ) #1 SMP Wed Dec 19 04:30:58 UTC 2012)

I have a samba share to a Windows SBS server mounted as /mnt/apshared under the apache user. I have created a directory inside this called &#39;webmeteor&#39;. I have created an app called &#39;myapp&#39; inside the &#39;webmeteor&#39; directory, so my directory is like so: /mnt/apshared/webmeteor/myapp.

I am logged in as root. When I try to run the app using the `meteor` command, I am given the following error messages:

    Unexpected mongo exit code 100. Restarting.
    Unexpected mongo exit code 100. Restarting.
    Unexpected mongo exit code 100. Restarting.
    Can&#39;t start mongod

    MongoDB had an unspecified uncaught exception.
    Check to make sure that MongoDB is able to write to its database directory.

My first point of call was this StackOverflow question: https://stackoverflow.com/questions/14496190/creating-a-new-meteor-js-file-and-get-error-100-mongodb-not-able-to-write -- however, following these suggestions (sudo&#39;ing the meteor command, and checking for disk space of which I have 70GB free) has not worked. I am quite certain that these issues are permission related.

I have tried to `chown` recursively to root:root (as I am logged in as root), and `chmod` to 777 recursively also, but to no avail.

I am asking you, what should I try next, to allow my Meteor app to start?

Thanks in advance.

Meteor: unexpected mongo exit code 100

I want to implement ProgressDialog like this one, without additional frame.:
![Pic][1]

 But I&#39;m getting this one. How could I change that?  

![enter image description here][2]

Here is my code for ProgressDialog.
Thanks in advance

   

    private ProgressDialog mProgressDialog;
       ............
       mProgressDialog = new ProgressDialog(activity);
       mProgressDialog.setIndeterminate(false);
       mProgressDialog.setProgressStyle(ProgressDialog.STYLE_SPINNER);
       ............
        public class ProgressTask extends AsyncTask &lt;Fragment,Void,Fragment&gt;{
        		@Override
        		protected void onPreExecute(){
        			mProgressDialog.show();
        		}
        		
        		@Override
        		protected Fragment doInBackground(Fragment... arg0) {	
                        //my stuff is here
        		}
        		
        		@Override
        		protected void onPostExecute(Fragment result) {
                       mProgressDialog.dismiss();
        	   	}
        	}

  [1]: http://i.stack.imgur.com/264Xa.png
  [2]: http://i.stack.imgur.com/B3BnF.png


ProgressDialog spinning circle

What is actually the difference between:

    this.HasRequired(a =&gt; a.Something)
        .WithMany()
        .Map(a =&gt; a.MapKey(&quot;SomethingId&quot;));


and


    this.HasRequired(a =&gt; a.Something)
        .WithMany()
        .HasForeignKey(a =&gt; a.SomethingId);


MapKey vs HasForeignKey Difference - Fluent Api

What is actually the difference between:
<pre><code class="hljs language-ini">this.HasRequired(a => a.Something)
 .WithMany()
 .Map(a => a.MapKey("SomethingId"));
</code></pre>
and
<pre><code class="hljs language-ini">this.HasRequired(a => a.Something)
 .WithMany()
 .HasForeignKey(a => a.SomethingId);
</code></pre>

When should one call `DbContext.dispose()` with entity framework?

1. **Is this imaginary method bad?** 

        public static string GetName(string userId)
        {
            var context = new DomainDbContext();
            var userName = context.UserNameItems.FirstOrDefault(x =&gt; x.UserId == userId);
            context.Dispose();
            return userName;
        }

22. **Is this better?**

        public static string GetName(string userId)
        {
            string userName;
            using(var context = new DomainDbContext()) {
                userName = context.UserNameItems.FirstOrDefault(x =&gt; x.UserId == userId);
                context.Dispose();
            }
            return userName;
        }

3. **Is this even better, that is, should one NOT call context.Dispose() when using using()?**

        public static string GetName(string userId)
        {
            string userName;
            using(var context = new DomainDbContext()) {
                userName = context.UserNameItems.FirstOrDefault(x =&gt; x.UserId == userId);
            }
            return userName;
        }

Entity Framework and calling context.dispose()

I&#39;ve got multiple classes (including TPT) in my project. Each POCO has a `BaseClass`, which has a `GUID` (called `GlobalKey`) as primary key.

First I used `DataAnnotations` to create correct foreign keys. But then I&#39;ve got problems synchronizing the corresponding GUID with the object itself.

Now I want to have only one virtual navigation property so that the GUID field in the database is created by `NamingConvention`. But the field name always adds an underscore followed by the word `GlobalKey` (which is right). When I want to remove the underscore, I don&#39;t want to go thru all my POCOs in the fluent API to do this:

    // Remove underscore from Navigation-Field     
    modelBuilder.Entity&lt;Person&gt;()
                .HasOptional(x =&gt; x.Address)
                .WithMany()
                .Map(a =&gt; a.MapKey(&quot;AddressGlobalKey&quot;));

Any ideas to do this for all POCOS by overwriting a convention?

Thanks in advance.

Andreas


How do I remove underscore of foreign key fields in code first by convention

I wanting to know how to run the &#39;Update-Database&#39; command for a production database.

The &#39;Update-Database&#39; database works fine from my local machine, but how do I get this to work for production data? 

So, if I make a change to my application and then run the &#39;publish&#39; through visual studio this works fine for the code side of things, but how do I run the &#39;Update-Database&#39; command for the production data.

Hope this question makes sense...

Thanks,

Entity framework code first - how to run Update-Database for production database

Ok, I have tri-leveled entities with the following hierarchy: Course -&gt; Module -&gt; Chapter

Here was the original EF LINQ statement:

    Course course = db.Courses
                    .Include(i =&gt; i.Modules.Select(s =&gt; s.Chapters))
                    .Single(x =&gt; x.Id == id); 

Now, I want to include another entity called Lab which is associated with a course.

How do I include the Lab entity?

I tried the following but it didn&#39;t work:

    Course course = db.Courses
                    .Include(i =&gt; i.Modules.Select(s =&gt; s.Chapters) &amp;&amp; i.Lab)
                    .Single(x =&gt; x.Id == id); 

Any ideas on including the 2nd Entity?

Any piece of advise or information would be highly appreciated. Thanks!

EF LINQ include multiple and nested entities

I&#39;m seeing some really strange perf related to a very simple query using Entity Framework Code-First with .NET framework version 4. The LINQ2Entities query looks like this:

     context.MyTables.Where(m =&gt; m.SomeStringProp == stringVar);

This takes over 3000 milliseconds to execute. The generated SQL looks very simple:

     SELECT [Extent1].[ID], [Extent1].[SomeStringProp], [Extent1].[SomeOtherProp],
     ...
     FROM [MyTable] as [Extent1]
     WHERE [Extent1].[SomeStringProp] = &#39;1234567890&#39;

This query runs almost instantaneously when run through Management Studio. When I change the C# code to use the SqlQuery function, it runs in 5-10 milliseconds:

     context.MyTables.SqlQuery(&quot;SELECT [Extent1].[ID] ... WHERE [Extent1].[SomeStringProp] = @param&quot;, stringVar);

So, exact same SQL, the resulting entities are change-tracked in both cases, but wild perf difference between the two. What gives?

Entity Framework query slow, but same SQL in SqlQuery is fast

I am using EF Code First with EF 5 in VS 2012. I use PM `update-database` command and I have a simple seed method to fill some tables with sample data.

I would like to delete and recreate my x.mdb. The update history seems to be out of sync. If I comment out all my DBSets in my context, `update-database` runs with no error but leaves some tables in the DB. As I have no valuable data in the DB it seems to the simplest to reset the all thing.

How can I accomplish this?

How to delete and recreate from scratch an existing EF Code First database

I&#39;ve been wrestling with this for a while and can&#39;t quite figure out what&#39;s happening.  I have a Card entity which contains Sides (usually 2) - and both Cards and Sides have a Stage.  I&#39;m using EF Codefirst migrations and the migrations are failing with this error: 

&gt; Introducing FOREIGN KEY constraint &#39;FK_dbo.Sides_dbo.Cards_CardId&#39; on
&gt; table &#39;Sides&#39; may cause cycles or multiple cascade paths. Specify ON
&gt; DELETE NO ACTION or ON UPDATE NO ACTION, or modify other FOREIGN KEY
&gt; constraints.

Here&#39;s my **Card** entity: 

    public class Card
    {
        public Card()
        {
            Sides = new Collection&lt;Side&gt;();
            Stage = Stage.ONE;
        }
     
        [Key]
        [Required]
        public virtual int CardId { get; set; }

        [Required]
        public virtual Stage Stage { get; set; }

        [Required]
        [ForeignKey(&quot;CardId&quot;)]
        public virtual ICollection&lt;Side&gt; Sides { get; set; }
    }

Here&#39;s my **Side** entity: 

    public class Side
    {
        public Side()
        {
            Stage = Stage.ONE;
        }

        [Key]
        [Required]     
        public virtual int SideId { get; set; } 

        [Required]
        public virtual Stage Stage { get; set; }

        [Required]
        public int CardId { get; set; }

        [ForeignKey(&quot;CardId&quot;)]
        public virtual Card Card { get; set; }

    }

And here&#39;s my **Stage** entity: 

    public class Stage
    {
        // Zero
        public static readonly Stage ONE = new Stage(new TimeSpan(0, 0, 0), &quot;ONE&quot;);
        // Ten seconds
        public static readonly Stage TWO = new Stage(new TimeSpan(0, 0, 10), &quot;TWO&quot;);

        public static IEnumerable&lt;Stage&gt; Values
        {
            get
            {
                yield return ONE;
                yield return TWO;
            }

        }

        public int StageId { get; set; }
        private readonly TimeSpan span;
        public string Title { get; set; }

        Stage(TimeSpan span, string title)
        {
            this.span = span;
            this.Title = title;
        }

        public TimeSpan Span { get { return span; } }
    }

What&#39;s odd is that if I add the following to my Stage class: 

        public int? SideId { get; set; }
        [ForeignKey(&quot;SideId&quot;)]
        public virtual Side Side { get; set; }

The migration runs successfully.  If I open up SSMS and look at the tables, I can see that `Stage_StageId` has been added to `Cards` (as expected/desired), however `Sides` contains no reference to `Stage` (not expected).  

If I then add 

        [Required]
        [ForeignKey(&quot;StageId&quot;)]
        public virtual Stage Stage { get; set; }
        public int StageId { get; set; }

To my Side class, I see `StageId` column added to my `Side` table.  

This is working, but now throughout my application, any reference to `Stage` contains a `SideId`, which is in some cases totally irrelevant.  **I&#39;d like to just give my `Card` and `Side` entities a `Stage` property based on the above Stage class without polluting the stage class with reference properties if possible**... what am I doing wrong?  

Introducing FOREIGN KEY constraint may cause cycles or multiple cascade paths - why?

I&#39;m using Entity Framework code first in my website and I&#39;m just wondering if there is any way to debug the migration codes. You know, like setting breakpoints and stuff like this. 

I&#39;m using Package Manager Console to update the database using `Update-Database`.

Thanks

Debug code-first Entity Framework migration codes

Following the &quot;Code First Modeling&quot; section of the [Pluralsight &quot;Getting Started with Entity Framework 5&quot; course by Julie Lerman][1], I created two POCO classes with a **one-to-zero-or-one** relationship: a parent (User) and an **optional** child (UserDetail).

[User and UserDetail data model diagram (click to view).][2]

Notice in the diagram that **the UserId property is a primary key and a foreign key for UserDetail**.

Relevant code:

    public class User
    {
        //...
        
        [Key]
        [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
        public int UserId { get; set; }
        
        /* Has a 1:0..1 relationship with UserDetail */
        public virtual UserDetail UserDetail { get; set; }

        //...
    }

    public class UserDetail
    {
        //...
        
        /* Has a 0..1:1 relationship with User */
        public virtual User User { get; set; }

        [Key, ForeignKey(&quot;User&quot;)]
        public int UserId { get; set; }
        
        //...
    }

    public class EFDbContext : DbContext
    {
        public DbSet&lt;User&gt; Users { get; set; }
        //public DbSet&lt;UserDetail&gt; UserDetails { get; set; }  /* Explicit declaration not necessary. Context is aware of UserDetail entity due to 0..1:1 relationship with User */

        public EFDbContext()
        {
            Configuration.ProxyCreationEnabled = true;
            Configuration.LazyLoadingEnabled = true;
        }
    }

    public class UserRepository : IUserRepository
    {
        private EFDbContext _context = new EFDbContext();

        public void Delete(User entity)
        {
            entity = _context.Users.Find(entity.UserId);

            //...

            _context.Users.Remove(entity);
            _context.SaveChanges();

            //...
        }
    }

When the Delete() method in the UserRepository class is called, it does not delete the User record in the database because the foreign key in UserDetail does not have cascade delete enabled.

&gt; The DELETE statement conflicted with the REFERENCE constraint &quot;FK_dbo.UserDetail_dbo.User_UserId&quot;.


How would you enable cascading deletes for **one-to-zero-or-one relationships** using Entity Framework Code First (so that deleting a User automatically deletes UserDetail)?


  [1]: http://pluralsight.com/training/Courses/TableOfContents/entity-framework5-getting-started
  [2]: http://i.imgur.com/9wLj4Kj.png

Entity Framework (EF) Code First Cascade Delete for One-to-Zero-or-One relationship

I want to generate an ER diagram of an SQL database using Microsoft [SQL Server Management Studio][1] (SMSS). However, I don’t know how to.

I found this technique online: *[Making ER Diagram from SQL Server 2008 Database][2]*

However, I am not able to see &quot;Database Node&quot; or &quot;Database Diagrams&quot; nodes as mentioned in the first and second steps.

Hence, how can I generate an ER diagram from an existing database?

From the comments, I realize that I was right in my understanding that *Database node* means the node with my database name. But then my problem is I am not able to find the &quot;Database Diagrams&quot; node under my Database name. What should I do so that I can see it?

PS: It’s not a local database.


  [1]: https://en.wikipedia.org/wiki/SQL_Server_Management_Studio
  [2]: http://forums.asp.net/t/1790223.aspx?Making%20ER%20Diagram%20from%20SQL%20Server%202008%20Database





Content Type	Original Author	Original Content on Stackoverflow
Question	parliament	View Question on Stackoverflow
Solution 1 - Entity Framework	Slauma	View Answer on Stackoverflow

MapKey vs HasForeignKey Difference - Fluent Api

Entity Framework Problem Overview

Entity Framework Solutions

Solution 1 - Entity Framework

ProgressDialog spinning circle

Meteor: unexpected mongo exit code 100

Attributions