POCOs(Plain old CLR objects) are simply entities of your Domain. Normally when we use entity framework the entities are generated automatically for you. This is great but unfortunately these entities are interspersed with database access functionality which is clearly against the SOC (Separation of concern). POCOs are simple entities without any data access functionality but still gives the capabilities all [EntityObject][1] functionalities like

 - Lazy loading 
 - Change tracking

Here is a good start for this

[POCO Entity framework][2]

You can also generate POCOs so easily from your existing Entity framework project using Code generators.

[EF 5.X DbContext code generator][3]


  [1]: http://msdn.microsoft.com/en-us/library/system.data.objects.dataclasses.entityobject.aspx
  [2]: https://msdn.microsoft.com/en-us/library/dd456853(v=vs.100).aspx
  [3]: http://visualstudiogallery.msdn.microsoft.com/da740968-02f9-42a9-9ee4-1a9a06d896a2

After looking around on the internet, I&#39;ve seen a lot of suggestions (use window.onkeypress, use jQuery, etc.) but for almost every option there&#39;s a counterargument. How can I  detect a keypress in Javascript? 


How do I detect keypresses in Javascript?

I have a double value which I have to display at my UI.
Now the condition is that the decimal value of double = 0 eg. - 14.0
In that case I have to show only 14 on my UI.
Also, the max limit for characters is 5 here.

eg.- 12.34  the integer value can be no bigger than 2 digits and so is the decimal value for our double.

What could be the best way of doing this?

How to check if a double value has no decimal part

I just started learning POCO but I cannot understand the usage and advantage. Even the following link of StackOverflow did not help me.

https://stackoverflow.com/questions/2672409/what-is-entity-framework-with-poco

Can anybody explain the usage of POCO with a simple example?

What is POCO in Entity Framework?

I just started learning POCO but I cannot understand the usage and advantage. Even the following link of StackOverflow did not help me.
<a href="https://stackoverflow.com/questions/2672409/what-is-entity-framework-with-poco" target="_blank" rel="noopener noreferrer">https://stackoverflow.com/questions/2672409/what-is-entity-framework-with-poco</a>
Can anybody explain the usage of POCO with a simple example?

We&#39;re working on Visual Studio 2010 and TFS 2010. We have our own BuildTemplate that is a copy of default template, but with some additions like (create Directory...), but the main point, that all that is in DefaultTemplate - is left.

We have witten &quot;unit&quot; tests that also are working. I have made Build definition that runs all the unit tests. Have read the information here - http://geekswithblogs.net/jakob/archive/2009/06/03/tfs-team-build-2010-running-unit-tests.aspx   and a lot of other places also.

Build runs just perfect, the only thing that is&#39;nt working is a Build summary - Test results, Code coverage like in the link above.

So when i&#39;m watching Activity log while building my application, it shows that:

    Run MSTest for Test Assemblies
    c:\Program Files (x86)\Microsoft Visual Studio 10.0\Common7\IDE\MSTest.exe /nologo /usestderr /testSettings:&quot;C:\Builds\7\**Project**\**BuildName**\Sources\**ProgramName**\**ProgNameAndVersion**\Solutions\**SolutionName**\localtestrunDebug.testrunconfig&quot; /searchpathroot:&quot;C:\Builds\7\**Project**\**BuildName**\Binaries&quot; /resultsfileroot:&quot;C:\Builds\7\**Project**\**BuildName**\TestResults&quot; /testcontainer:&quot;C:\Builds\7\**Project**\**BuildName**\Binaries\**TestProjectName**.dll&quot; /publish:&quot;http://***:8080/tfs/MSLN&quot; /publishbuild:&quot;***:///Build/Build/14599&quot; /teamproject:&quot;**ProjectName**&quot; /platform:&quot;x86&quot; /flavor:&quot;**Release**&quot; 
    Loading C:\Builds\7\**Project**\**BuildName**\Sources\**ProgramName**\**ProgNameAndVersion**\Solutions\**SolutionName**\localtestrunDebug.testrunconfig...
    Loading C:\Builds\7\**Project**\**BuildName**\Binaries\**TestProjectName**.dll...
    Starting execution...
    
    Results               Top Level Tests
    -------               ---------------
    Failed                ***.Test.***
    Failed                ***.Test.***
    Failed                ***.Test.***
    Passed                ***.Test.***
    Passed                ***.Test.***
    Inconclusive          ***.Test.***
    Inconclusive          ***.Test.***
    Passed                ***.Test.***
    &lt;many other tests&gt;
    ...
    5/154 test(s) Passed, 147 Failed, 2 Inconclusive
    
    Summary
    -------
    Test Run Failed.
    Failed        147
    Passed          5
    Inconclusive    2
    -----------------
    Total         154
    Results file:  C:\Builds\7\**Project**\**BuildName**\TestResults\***tfsbuild_***TFSBUILDER 2013-04-19 10_03_42_x86_Release.trx
    Test Settings: Local Test Run

And at the end of the Build summary is blank:

1 projects/solutions compiled
 No Test Results
 No Code Coverage Results

**Why does it not show test results like in the link:** http://geekswithblogs.net/jakob/archive/2009/06/03/tfs-team-build-2010-running-unit-tests.aspx

I&#39;m a starter in TFS so help me with this by giving advices in simple language =)

This link seems to have moved to (edited 2019-09-23): https://blog.ehn.nu/2009/06/tfs-team-build-2010-executing-unit-tests/

TFS Build Test Results

I have a Model with 4 properties which are of type string. I know you can validate the length of a single property by using the StringLength annotation. However I want to validate the length of the 4 properties combined. 

What is the MVC way to do this with data annotation?

I&#39;m asking this because I&#39;m new to MVC and want to do it the correct way before making my own solution.

ASP.NET MVC: Custom Validation by DataAnnotation

I am curious about how the `Tuple&lt;T1, T2, T3, ...&gt;` serializes and deserializes. I searched using keywords &quot;json&quot; and &quot;tuple&quot; but I could not find what I want.

How does a Tuple serialize to and deserialize from JSON?

Imagine the code:

    public class obj
    {
        // elided
    }
    
    public static Dictionary&lt;string, obj&gt; dict = new Dictionary&lt;string, obj&gt;();

**Method 1**

    public static obj FromDict1(string name)
    {
        if (dict.ContainsKey(name))
        {
            return dict[name];
        }
        return null;
    }

**Method 2**

    public static obj FromDict2(string name)
    {
        try
        {
            return dict[name];
        }
        catch (KeyNotFoundException)
        {
            return null;
        }
    }

I was curious if there is a difference in performance of these 2 functions, because the first one SHOULD be SLOWER than second one - given that it needs to check twice if the dictionary contains a value, while second function does need to access the dictionary only once but WOW, it&#39;s actually opposite:

Loop for 1 000 000 values (with 100 000 existing and 900 000 non existing):

&gt; first function: 306 milliseconds
&gt; 
&gt; second function: 20483 milliseconds

Why is that?

EDIT: As you can notice in comments below this question, the performance of second function is actually slightly better than first one in case there are 0 non existing keys. But once there is at least 1 or more non existing keys, the performance of second one decrease rapidly.

Why is it faster to check if dictionary contains the key, rather than catch the exception in case it doesn&#39;t?

I recently found out that by default MessageBoxes were not the top most form when displayed by default and I was wondering if anyone knew any circumstances when you wouldn&#39;t want the messagebox to be shown on top of other windows?

I found the issue when I started to show splash screens whilst loading an application, and it looked like my program was still running but there was a `MessageBox` behind the splash screen that was waiting for input.. The splash screen was shown on a different thread to the thread that called the messagebox so I imagine this is why it didn&#39;t appear above the splash; but this still doesn&#39;t explain why MessageBox doesn&#39;t have the `MB_TOPMOST` flag by default?

**Edit**

To better clarify:
in the end I had to do something similar to this in the end to make a messagebox, code isn&#39;t exactly correct as wrote from memory)

    [DllImport(&quot;User32.dll&quot;)]
    private int extern MessageBox(windowhandle, message, caption, flag);
    public static void MessageBox(windowhandle, string message, string caption)
    {
        MessageBox(windowhandle, message,caption, MB_TOPMOST);
    }

Why isn&#39;t MessageBox TopMost?

I have an ansyc method


    public Task&lt;Car&gt; GetCar()
    {

    }

I can call this method async and await:

     Car car = await GetCar()

How can I invoke the method using MethodInfo.Invoke and await for the result asynchronously.

     MethodInfo method = obj.GetMethod(&quot;GetCar&quot;);
     method.Invoke( obj, null)

.Net Invoke async method and await

I have below code in c# 4.0.

    //Dictionary object with Key as string and Value as List of Component type object
    Dictionary&lt;String, List&lt;Component&gt;&gt; dic = new Dictionary&lt;String, List&lt;Component&gt;&gt;();
    
    //Here I am trying to do the loping for List&lt;Component&gt;
    foreach (List&lt;Component&gt; lstComp in dic.Values.ToList())
    {
    	// Below I am trying to get first component from the lstComp object.
        // Can we achieve same thing using LINQ?
        // Which one will give more performance as well as good object handling?
    	Component depCountry = lstComp[0].ComponentValue(&quot;Dep&quot;);
    }



How to get first object out from List&lt;Object&gt; using Linq

I often find myself creating a [`Dictionary`][dict] with a non-trivial value class (e.g. [`List`][list]), and then always writing the same code pattern when filling in data.

For example:

&lt;!-- language: lang-csharp --&gt;

    var dict = new Dictionary&lt;string, List&lt;string&gt;&gt;();
    string key = &quot;foo&quot;;
    string aValueForKey = &quot;bar&quot;;

That is, I want to insert `&quot;bar&quot;` into the list that corresponds to key `&quot;foo&quot;`, where key `&quot;foo&quot;` might not be mapped to anything.

This is where I use the ever-repeating pattern:

&lt;!-- language: lang-csharp --&gt;

    List&lt;string&gt; keyValues;
    if (!dict.TryGetValue(key, out keyValues))
      dict.Add(key, keyValues = new List&lt;string&gt;());
    keyValues.Add(aValueForKey);

Is there a more elegant way of doing this?

Related questions that don&#39;t have answers to this question:

* [Is there an IDictionary implementation that returns null on missing key instead of throwing?][1]
* [Find-or-insert with only one lookup in c# dictionary][2]
* [Dictionary returning a default value if the key does not exist][3]

 [dict]: http://msdn.microsoft.com/en-us/library/xfhwa508.aspx
 [list]: http://msdn.microsoft.com/en-us/library/6sh2ey19.aspx
 [1]: https://stackoverflow.com/q/538729/974531
 [2]: https://stackoverflow.com/q/6408916/974531
 [3]: https://stackoverflow.com/q/2601477/974531

.NET Dictionary: get or create new

Java 1.8 is receiving the `Optional&lt;T&gt;` class, that allows us to explicitly say when a method may return a null value and &quot;force&quot; its consumer to verify if it is not null (`isPresent()`) before using it.

I see C# has `Nullable&lt;T&gt;`, that does something similar, but with basic types. It seems to be used for DB queries, to distinguish when a value exists and is 0 from when it doesn&#39;t exist and is null.

But it seems that C#&#39;s `Nullable&lt;T&gt;`doesn&#39;t work for objects, only for basic types, while Java&#39;s `Optional&lt;T&gt;` only works for objects and not for basic types.

Is there a Nullable/Optional class in C#, that forces us to test if object exists before extracting and using it?

Optional return in C#.Net

This is probably the biggest waste of time problem I have spent hours on solving for a long time.


	var db = new hublisherEntities();
	establishment_brands est = new establishment_brands();
	
	est.brand_id = 1;
	est.establishment_id = 1;
	est.price = collection[&quot;price&quot;];
	est.size = collection[&quot;size&quot;];

	db.establishment_brands.Add(est);
	db.SaveChanges();

This gives me an error of

&gt; Value cannot be null. Parameter name: source

stacktrace of

&gt; [ArgumentNullException: Value cannot be null. Parameter name: source] 
&gt; System.Linq.Enumerable.Any(IEnumerable`1 source, Func`2 predicate)
&gt; +4083335    System.Data.Entity.Internal.InternalContext.WrapUpdateException(UpdateException
&gt; updateException) +87   
&gt; System.Data.Entity.Internal.InternalContext.SaveChanges() +193   
&gt; System.Data.Entity.Internal.LazyInternalContext.SaveChanges() +33   
&gt; System.Data.Entity.DbContext.SaveChanges() +20 ... ...

I just want to add an entity to the table. The ORM is EF.

Value cannot be null. Parameter name: source

I have a desktop client application that uses modal windows to set properties for hierarchical objects. Since this is a client application and access to the DbContext is not threaded, I use a long-running context on the main Form that gets passed around to modal children.

These modal windows use the PropertyGrid to display entity properties and also have cancel buttons. If any data is modified and the cancel button is pressed, the changes are reflected in the parent form (where I cannot dispose the `DbContext object`).

Is there a way to discard any changes made if the `DbContext.SaveChanges()` method has NOT been called?

**UPDATE:** Entity Framework Version 4.4.

DbContext discard changes without disposing

I have 4 projects : 

    Toombu.Entities : all models are there
    Toombu.DataAccess: Mapping, Repository and ToombuContext
    Toombu.Logique : Logic of my application
    Toombu.Web : MVC 4 application. With all others DLL.

I tried to enable migration in **Toombu.Web** but i had this error :

    No context type was found in the assembly

How can I enable migration ?

EF 5 Enable-Migrations : No context type was found in the assembly

Well, I have one-to-many related model:

    public class Parent
    {
        public int Id { get; set; }
        public string Name { get; set; }
        public ICollection&lt;Child&gt; Children { get; set; }
    }
    
    public class Child
    {
        public int Id { get; set; }
        public string ChildName { get; set; }
    }

What I want to do is clear `Parent.Children` and remove related child entities from database. I&#39;ve already tried:

**Database context class:**

    modelBuilder.Entity&lt;Parent&gt;()
                .HasMany(p =&gt; p.Children)
                .WithOptional()
                .WillCascadeOnDelete(true);

this works fine, but I still have redundant records in database with `Parent_Id = null` fields when I do 

    parent.Children.Clear();
    repository.InsertOrUpdate(parent);

 in my repository class. Also the same behavior is when I do:

    modelBuilder.Entity&lt;Parent&gt;()
                .HasMany(pr =&gt; pr.Children)
                .WithOptional(ri =&gt; ri.Parent)
                .WillCascadeOnDelete(true);

with additional `Parent` property in `Child` class

    public class Child
    {
        ...
        public Parent Parent { get; set; }
        ...
    }

or when I do

    modelBuilder.Entity&lt;Child&gt;()
                .HasOptional(p =&gt; p.Parent)
                .WithMany(p =&gt; p.Children)
                .HasForeignKey(p =&gt; p.Parent_Id)
                .WillCascadeOnDelete(true);


with additional Parent_Id property in `Child` class

    public class Child
    {
         ...
         public int Parent_Id { get; set; }
         ...
    }
        

**So, how can I configure cascade deleting correctly? Or how should I supposed to remove those child entities? I assume this is casual task but I&#39;m just missing something.**

How to remove child one to many related records in EF code first database?

Here&#39;s what I am looking at

    PM&gt; Add-Migration AddedSubdivion -StartUpProjectName Data -Verbose
    Using StartUp project &#39;Data&#39;.
    Using NuGet project &#39;Registry&#39;.
    Could not load assembly &#39;Registry&#39;. (If you are using Code First Migrations inside 
    Visual Studio this can happen if the startUp project for your solution does not 
    reference the project that contains your migrations. You can either change the startUp 
    project for your solution or use the -StartUpProjectName parameter.)

I have no idea why it&#39;s trying to reference the `Registry` project. `Registry` depends on `Data`, not the other way around. I am very new to this, so I&#39;d appreciate any help. 

Content Type	Original Author	Original Content on Stackoverflow
Question	user1556433	View Question on Stackoverflow
Solution 1 - C#	Prabhu Murthy	View Answer on Stackoverflow

What is POCO in Entity Framework?

C# Problem Overview

C# Solutions

Solution 1 - C#

How to check if a double value has no decimal part

How do I detect keypresses in Javascript?

Attributions