Yup - it&#39;s not that straightforward.

Here&#39;s what you do:

1 - Right click on the designer, **Add** -&gt; **Association**

2 - Setup the association and cardinalities (People *..1 Gender, People *..1 Race)

3 - Go into the **Model Browser** -&gt; **Associations**

4 - Right click on your newly created associations, click **Properties**

5 - Here you need to setup the endpoints for the key and cascade options. Make sure you get the endpoints correct. You can also setup a referential constraint here for your implicit navigational property.

6 - Map the navigational property to the relevant tables/fields.

7 - Validate your model, cross your fingers.

Hope this helps.

I came across [this blog post](http://ihadthisideaonce.com/2012/01/18/manually-creating-referential-constraints-in-entity-framework-4/) which proposes the following solution, which worked great for me (unfortunately I could not get RPM1984&#39;s to work in my situation).

 1. Add an Association via designer background right click contextual menu
 2. Set up your Association (be sure to uncheck creation of foreign key)
 3. Right click on the association and choose Properties
 4. Click on the &lt;kbd&gt;...&lt;/kbd&gt; button for Referential Constraint
 5. Set up the relation between the keys within
 6. Verify (from the designer contextual menu)
 7. ???
 8. Profit!

Is it a web server or a programming language for server-side scripts?

What exactly is node.js used for?

Given a huge collection of objects, is there a performance difference between the the following?

[Collection.Contains][1]:

    myCollection.Contains(myElement)


[Enumerable.Any][2]:

    myCollection.Any(currentElement =&gt; currentElement == myElement)


  [1]: http://msdn.microsoft.com/en-us/library/ms132407.aspx
  [2]: http://msdn.microsoft.com/en-us/library/bb534972.aspx

LINQ Ring: Any() vs Contains() for Huge Collections

I generated an Entity Framework Model (4.0) from my database. I did not design the database and do not have any control over the schema, but there are a few tables that do not have foreign key constraints defined, but there is an implicit relationship defined.

For example:

I have a table called People that has the following columns:
GenderID
RaceID

There are tables for both Gender and Race but there is no foreign key in the People table.

When I imported the model it did not add Navigation Properties for these relationships. I tried to add it manually but From Role and To Role are disabled. I&#39;m not sure how to add the relationship myself. How do I do this?

Entity Framework - Add Navigation Property Manually

I generated an Entity Framework Model (4.0) from my database. I did not design the database and do not have any control over the schema, but there are a few tables that do not have foreign key constraints defined, but there is an implicit relationship defined.
For example:
I have a table called People that has the following columns:
GenderID
RaceID
There are tables for both Gender and Race but there is no foreign key in the People table.
When I imported the model it did not add Navigation Properties for these relationships. I tried to add it manually but From Role and To Role are disabled. I'm not sure how to add the relationship myself. How do I do this?

    @{ int i = 4; }
    @foreach (string s in &quot;1,2,3&quot;.Split(&#39;,&#39;)) {
       @:s is equal to @s
       @{ i++; }
    }

I get &quot;No overload for method &#39;Write&#39; takes 0 arguments&quot; on the @{ i++; } line of code.  Any thoughts?  Thanks!

Razor: No overload for method &#39;Write&#39; takes 0 arguments

I have developed an application and installed it on a client computer. In my application I need to get its installation path. My application has a registry entry at: 

&lt;!-- language: none --&gt;

    HKEY_LOCAL_MACHINE\SOFTWARE\MyApplication\[AppPath]

How can I read `AppPath` using C#?


Reading a registry key in C#

I&#39;m having another of these &quot;Could not load file or assembly or one of its dependencies&quot; problems.

&gt; Additional information: Could not load
&gt; file or assembly
&gt; &#39;Microsoft.Practices.Unity,
&gt; Version=1.2.0.0, Culture=neutral,
&gt; PublicKeyToken=31bf3856ad364e35&#39; or
&gt; one of its dependencies. The located
&gt; assembly&#39;s manifest definition does
&gt; not match the assembly reference.
&gt; (Exception from HRESULT: 0x80131040)

I have no idea what is causing this or how I could debug it to find the cause.

I&#39;ve done a search in my solution catalogs .csproj files, and every where I have Unity I have:

&gt; Reference
&gt; Include=&quot;Microsoft.Practices.Unity,
&gt; Version=2.0.414.0, Culture=neutral,
&gt; PublicKeyToken=31bf3856ad364e35,
&gt; processorArchitecture=MSIL&quot;

Can&#39;t find any reference anywhere which goes against 1.2.0.0 in any of my projects.

Any ideas how I should go about solving this?

Could not load file or assembly or one of its dependencies

The company I work for uses C++ Builder 6.  We&#39;ve been developing native code since conception. Our flagship product is written completely in native code.  

Enters the .NET Framework with its bells and whistles.  I fall, hook, line and sinker.  I convince management that .NET should absolutely be our new framework for all new software development and that we should start migrating our existing codeline ASAP.  With all the benefits it doesn&#39;t take much convincing.  They accept my proposal as usual.  

At this point I start developing my very first .NET application.  It&#39;s all going as planned.  The project is only one component of our product.  And so I get to the point of creating an installer for this new component.  As a company we pride ourselves in making things for the user as easy as possible.  Even Microsoft with thousands of developers don&#39;t create installers like we do.  When you install Microsoft CRM for instance, you will only get a list of failures and prerequisites that needs installing before you can continue.  Not us.  Never.  If you need something, we will install it for you.

This makes our installations feel so easy.  .NET Framework not installed?  No problem!  We&#39;ll do it for you.  Need SQL Native client?  Fine!

The issue is this, now that one single component of our solution is written in .NET, it complicates the installation process incredibly.  Before I can even get to installing our product, I need to do the following:

 - Detect whether the prerequisite is installed
   
 - Install it if it isn&#39;t

 - Verify that it was installed successfully

 - Next prerequisite

To install .NET Framework, I need the Windows Installer 4.5 first.  But there are different versions for the different OSes, so I add OS detection and launch the correct EXE.  Oh, .NET framework is already packaged with 2k8 and the installer exe cannot run on it, you have to run OCSetup.exe with parameters to install it.

And so it carries on.  Then SQL Express 2005 needs to be installed.  The dependencies increase once again.

I argue with management that even Microsoft don&#39;t make it this easy for the user.  Their response is that there is no reason for us to not be better than them in this way.  I can&#39;t argue with that except that I feel that there are very good reasons they&#39;ve gone with their approach.

Suddenly, our installer is massive.  All the prerequisites for .NET, not even talking about 64 bit support which has a whole separate range of EXEs to install.  So now it gets to the point where we want users to be able to download a &quot;quick&quot; evaluation.  What a joke.  You need to download 500MB to get a 30MB application running.  The majority of the installation package is prerequisites.

Management feels that we have too many dependencies/prerequisites.  I understand completely.  They suggest we move away from the .NET framework, back into native land where things were still &quot;easy&quot; in terms of installation.  This is where the one part of me wants to stand up for .NET explaining the benefits in the big picture, the improved development experience, easier maintenance and overall code quality.  The other part of me agrees with them wholeheartedly!  Developing in .NET simply requires you to install too many other prerequisites which complicates the installation.

Yes, some of the .NET advocates will claim that everything should be installed on a patched and updated operating system.  This is true, but not all customers have this, and simply saying &quot;I&#39;m sorry, update first&quot; just won&#39;t cut it.  Remember, we pride ourselves in the overall user experience.

We are now considering writing native code again and I know we&#39;re losing in terms of development speed and all the goodies of .NET.  But we are gaining in this area, be it small if you look at the big picture or not.  As we have native code development skills and .NET is actually new ground for us, it even makes sense to move back.

My question is this: what is your company&#39;s view on this issue if it even is an issue at all and what will the business case look like that I propose to management assuming I want to continue migrating all our products to .NET?

The case for or against .NET (the beast)

I have a program which outputs various results onto a command line console.

How do I save the output to a text file using a `StreamReader` or other techniques?


    System.Collections.Generic.IEnumerable&lt;String&gt; lines = File.ReadAllLines(@&quot;C:\Test\ntfs8.txt&quot;);

    foreach (String r in lines.Skip(1))
    {
        String[] token = r.Split(&#39;,&#39;);
        String[] datetime = token[0].Split(&#39; &#39;);
        String timeText = datetime[4];
        String actions = token[2];
        Console.WriteLine(&quot;The time for this array is: &quot; + timeText);
        Console.WriteLine(token[7]);
        Console.WriteLine(actions);
        MacActions(actions);
        x = 1;
        Console.WriteLine(&quot;================================================&quot;);
    }

    if (x == 2)
    {
        Console.WriteLine(&quot;The selected time does not exist within the log files!&quot;);
    }

    System.IO.StreamReader reader = ;
    string sRes = reader.ReadToEnd();
    StreamWriter SW;
    SW = File.CreateText(&quot;C:\\temp\\test.bodyfile&quot;);
    SW.WriteLine(sRes);
    SW.Close();
    Console.WriteLine(&quot;File Created&quot;);
    reader.Close();

How to Save Console.WriteLine Output to Text File

I have the following EF query:

    TestEntities db = new TestEntities();
    var questions = from q in db.Questions.Include(&quot;QuestionType&quot;)
                    from sq in db.SurveyQuestions
                    where sq.Survey == surveyTypeID
                    orderby sq.Order
                    select q;

    foreach( var question in questions ) {
        // ERROR: Null Reference Exception
        Console.WriteLine(&quot;Question Type: &quot; + question.QuestionType.Description);
    }
      
I am getting a null reference exception when I access the QuestionType property. I am using Include(&quot;QuestionType&quot;) but it doesn&#39;t appear to be working. What am I doing wrong?

**Edit**: It does not throw a null reference exception when I have Lazy Loading turned on.

**Edit**: Include() seems to be working when i do the following:

    var questions = db.Questions.Include(&quot;QuestionType&quot;).Select(q =&gt; q);

When I predicate on a separate entity Include seems to fail. Is that not allowed when using Include? What about my query is causing this thing to not work?

Entity Framework Include() is not working

How can I do this `SQL` query with `Entity Framework`? 

    SELECT DISTINCT NAME FROM TestAddresses

 

Entity Framework select distinct name

The following is the code sample: 
   

 

    private void loadCustomer(int custIdToQuery) 
        {
            var dbContext = new SampleDB();
            try
            {
                var customerContext = from t in dbContext.tblCustomers		// keeps throwing:
                                       where t.CustID.Equals(custIdToQuery)	// Unable to create a constant value of type &#39;System.Object&#39;. 
                                       select new							// Only primitive types (&#39;such as Int32, String, and Guid&#39;) 
                                       {									// are supported in this context.
                                           branchId = t.CustomerBranchID,	//
                                           branchName = t.BranchName		//
                                       };									//
    
                if (customerContext.ToList().Count() &lt; 1) //Already Tried customerContext.Any()
                {
                    lstbCustomers.DataSource = customerContext;
                    lstbCustomers.DisplayMember = &quot;branchName&quot;;
                    lstbCustomers.ValueMember = &quot;branchId&quot;;
                }
                else
                {
                    lstbCustomers.Items.Add(&quot;There are no branches defined for the selected customer.&quot;);
                    lstbCustomers.Refresh();
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
            finally
            {
                dbContext.Dispose();
            }
        }

i am unable to understand what am i doing wrong. I keep getting **&quot;Unable to create a constant value of type &#39;System.Object&#39;. Only primitive types (&#39;such as Int32, String, and Guid&#39;) are supported in this context.&quot;**

Linq Query keeps throwing &quot;Unable to create a constant value of type System.Object....&quot;, Why?

The only way that my WCF service can return classes from a code first model is by setting the `ProxyCreationEnable` to `false` using the code below.

    ((IObjectContextAdapter)MyDb).ObjectContext.ContextOptions.ProxyCreationEnable = false;

What are the negative consequences of doing this?  One gain is that I can at least get these dynamic types serialized so they can be sent over the wire using WCF.

What are the downsides to turning off ProxyCreationEnabled for CTP5 of EF code first

Is it possible to have Entity Framework (I am using the Code First Approach with CTP5 currently) store all DateTime values as UTC in the database?

Or is there maybe a way to specify it in the mapping, for example in this one for the last_login column:

    modelBuilder.Entity&lt;User&gt;().Property(x =&gt; x.Id).HasColumnName(&quot;id&quot;);
    modelBuilder.Entity&lt;User&gt;().Property(x =&gt; x.IsAdmin).HasColumnName(&quot;admin&quot;);
    modelBuilder.Entity&lt;User&gt;().Property(x =&gt; x.IsEnabled).HasColumnName(&quot;enabled&quot;);
    modelBuilder.Entity&lt;User&gt;().Property(x =&gt; x.PasswordHash).HasColumnName(&quot;password_hash&quot;);
    modelBuilder.Entity&lt;User&gt;().Property(x =&gt; x.LastLogin).HasColumnName(&quot;last_login&quot;);

Entity Framework DateTime and UTC

I&#39;ve seen many articles about how to overcome this matter, all related to CTP4, Or adding my own extension methods.

Is there an &quot;official&quot; EF4 included way to use lambda expressions inside include (for both first level relations and also 2nd and more level) or is it eventually was not included in the RTM ? 

It there is one - I would be glad to learn how to do it, as using lambda expression in my code now (with #system.data.entity #system.data.linq) still gives me: 

Cannot convert lambda expression to type &#39;string&#39; because it is not a delegate type	
on: 

&lt;!-- language: c# --&gt;

    var customers = from c in
    context.Customers.Include(c=&gt;c.Phone)


Using Include in Entity Framework 4 with lambda expressions

I&#39;m trying out Entity Framework 4&#39;s Code First (EF CodeFirst 0.8) and am running into a problem with a simple model that has a 1 &lt;--&gt; 0..1 relationship, between `Person` and `Profile`. Here&#39;s how they&#39;re defined:

    public class Person
    {
        public int PersonId { get; set; }

        public string FirstName { get; set; }
        public string LastName { get; set; }
        public DateTime? DOB { get; set; }

        public virtual Profile Profile { get; set; }
    }

    public class Profile
    {
        public int ProfileId { get; set; }
        public int PersonId { get; set; }
        public string DisplayName { get; set; }

        public virtual Person Person { get; set; }
    }

The DB context looks like this:

    public class BodyDB : DbContext
    {
        public DbSet&lt;Person&gt; People { get; set; }   
    }

I didn&#39;t define a `DbSet` for `Profile` because I consider `People` to be its aggregate root. When I try to add a new `Person` - even one without a `Profile` with this code:

    public Person Add(Person newPerson)
    {
        Person person = _bodyBookEntities.People.Add(newPerson);
        _bodyBookEntities.SaveChanges();
        return person;
    }

I get the following error:

&gt; Cannot insert explicit value for identity column in table &#39;People&#39; when IDENTITY_INSERT is set to OFF. 

The `newPerson` object has a `0` for the `PersonId` property when I call `People.Add()`. The database tables are `People` and `Profiles`. `PersonId` is the PK of `People` and is an auto-increment Identity. `ProfileId` is the PK of `Profiles` and is an auto-incement Identity. `PersonId` is a non-null int column of `Profiles`.

What am I doing wrong? I think I&#39;m adhering to all the EF Code First&#39;s convention over configuration rules.

EF Code First giving me error Cannot insert explicit value for identity column in table &#39;People&#39; when IDENTITY_INSERT is set to OFF.

I&#39;m working with MVC3, and using Entity Framework 4.0 Entities as my model.  So far, everything works great as far as using it as a model (all the crud operations/page generations work out of the box).  I&#39;m wondering, though, how do you get the same robust labels and validation information as when you generate a model manually?

Here&#39;s an example of what I mean. This is a class generated by the sample MVC3 project:

    public class LogOnModel
    {
        [Required]
        [Display(Name = &quot;User name&quot;)]
        public string UserName { get; set; }

        [Required]
        [DataType(DataType.Password)]
        [Display(Name = &quot;Password&quot;)]
        public string Password { get; set; }

        [Display(Name = &quot;Remember me?&quot;)]
        public bool RememberMe { get; set; }
    }

With the example above, you can specify what gets rendered in a label for the field (Display), and what type of field to use (Password).  However, when I try to use the entity framework and push it to the view below, I see the automatically generated labels are just the field names, and not anything I want the user to see/have to read:


    @using (Html.BeginForm()) {
        @Html.ValidationSummary(true)
        &lt;fieldset&gt;
            &lt;legend&gt;Person&lt;/legend&gt;
    
            &lt;div class=&quot;editor-label&quot;&gt;
                @Html.LabelFor(model =&gt; model.FirstName)
            &lt;/div&gt;
            &lt;div class=&quot;editor-field&quot;&gt;
                @Html.EditorFor(model =&gt; model.FirstName)
                @Html.ValidationMessageFor(model =&gt; model.FirstName)
            &lt;/div&gt;
    
            &lt;div class=&quot;editor-label&quot;&gt;
                @Html.LabelFor(model =&gt; model.MiddleName)
            &lt;/div&gt;
            &lt;div class=&quot;editor-field&quot;&gt;
                @Html.EditorFor(model =&gt; model.MiddleName)
                @Html.ValidationMessageFor(model =&gt; model.MiddleName)
            &lt;/div&gt;
    
            &lt;div class=&quot;editor-label&quot;&gt;
                @Html.LabelFor(model =&gt; model.LastName)
            &lt;/div&gt;
            &lt;div class=&quot;editor-field&quot;&gt;
                @Html.EditorFor(model =&gt; model.LastName)
                @Html.ValidationMessageFor(model =&gt; model.LastName)
            &lt;/div&gt;
    
            &lt;div class=&quot;editor-label&quot;&gt;
                @Html.LabelFor(model =&gt; model.Birthdate)
            &lt;/div&gt;
            &lt;div class=&quot;editor-field&quot;&gt;
                @Html.EditorFor(model =&gt; model.Birthdate)
                @Html.ValidationMessageFor(model =&gt; model.Birthdate)
            &lt;/div&gt;
    
            &lt;p&gt;
                &lt;input type=&quot;submit&quot; value=&quot;Create&quot; /&gt;
            &lt;/p&gt;
        &lt;/fieldset&gt;}

![enter image description here][1]


**My question is:** How do I add these extra decorations to the entities that are generated using EF4?  Is there something besides System.ComponentModel.DataAnnotations that I should be using? I know entities get regenerated and it&#39;s probably not a good idea to add this to entities&#39; code directly, but for some reason I can&#39;t think of a better approach than manually entering the label text in the view (lame, there&#39;s no reason to have to do that, this is MVC!).  I want to keep it so that the application is dynamic enough to be able to have the correct display information for my model come through and keep an MVC approach.  How do I do it?


  [1]: http://i.stack.imgur.com/N6ZbE.png

Using System.ComponentModel.DataAnnotations with Entity Framework 4.0

I currently have a repository for just about every table in the database and would like to further align myself with DDD by reducing them to aggregate roots only.

Let’s assume that I have the following tables, `User` and `Phone`.  Each user might have one or more phones.  Without the notion of aggregate root I might do something like this:

	//assuming I have the userId in session for example and I want to update a phone number
	List&lt;Phone&gt; phones = PhoneRepository.GetPhoneNumberByUserId(userId);
	phones[0].Number = “911”;
	PhoneRepository.Update(phones[0]);

The concept of aggregate roots is easier to understand on paper than in practice.  I will never have phone numbers that do not belong to a User, so would it make sense to do away with the PhoneRepository and incorporate phone related methods into the UserRepository?  Assuming the answer is yes, I’m going to rewrite the prior code sample.

Am I allowed to have a method on the UserRepository that returns phone numbers? Or should it always return a reference to a User, and then traverse the relationship through the User to get to the phone numbers:

	List&lt;Phone&gt; phones = UserRepository.GetPhoneNumbers(userId);
	// Or
	User user = UserRepository.GetUserWithPhoneNumbers(userId); //this method will join to Phone

Regardless of which way I acquire the phones, assuming I modified one of them, how do I go about updating them?  My limited understanding is that objects under the root should be updated through the root, which would steer me towards choice #1 below.  Although this will work perfectly well with Entity Framework, this seems extremely un-descriptive, because reading the code I have no idea what I’m actually updating, even though Entity Framework is keeping tab on changed objects within the graph.

	UserRepository.Update(user);
	// Or
	UserRepository.UpdatePhone(phone);

Lastly, assuming I have several lookup tables that are not really tied to anything, such as `CountryCodes`, `ColorsCodes`, `SomethingElseCodes`.  I might use them to populate drop downs or for whatever other reason.  Are these standalone repositories?  Can they be combined into some sort of logical grouping/repository such as `CodesRepository`?  Or is that against best practices.


Reducing Repositories to Aggregate Roots

I had seen some books(e.g *programming entity framework code first Julia Lerman*) define their domain classes (POCO) with no initialization of the navigation properties like:

&lt;!-- language: c# --&gt;

    public class User
    {
        public int Id { get; set; }
        public string UserName { get; set; }
    
        public virtual ICollection&lt;Address&gt; Address { get; set; }
        public virtual License License { get; set; }
    }
some other books or tools (e.g *Entity Framework Power Tools*) when generates POCOs initializes the navigation properties of the the class, like:

&lt;!-- language: c# --&gt;

    public class User
    {
        public User()
        {
            this.Addresses = new IList&lt;Address&gt;();
            this.License = new License();
        }
        public int Id { get; set; }
        public string UserName { get; set; }
    
        public virtual ICollection&lt;Address&gt; Addresses { get; set; }
        public virtual License License { get; set; }
    }

&lt;h3&gt;Q1: Which one is better? why? Pros and Cons?&lt;/h3&gt;

**Edit:**

&lt;!-- language: c# --&gt;

    public class License
    {
        public License()
        {
            this.User = new User();
        }
        public int Id { get; set; }
        public string Key { get; set; }
        public DateTime Expirtion { get; set; }

        public virtual User User { get; set; }
    }

&lt;h3&gt;Q2: In second approach there would be stack overflow if the `License` class has a reference to `User` class too. It means we should have one-way reference.(?) How we should decide which one of the navigation properties should be removed?&lt;/h3&gt;

EF codefirst : Should I initialize navigation properties?

As I remember in EF  [navigation property should be virtual][1]:

    public class Blog 
    {  
        public int BlogId { get; set; }  
        public string Name { get; set; }  
        public string Url { get; set; }  
        public string Tags { get; set; }  
    
        public virtual ICollection&lt;Post&gt; Posts { get; set; }  
    }

But I look at [EF Core][2] and don&#39;t see it as virtual:

    public class Student
        {
            public int ID { get; set; }
            public string LastName { get; set; }
            public string FirstMidName { get; set; }
            public DateTime EnrollmentDate { get; set; }
    
            public ICollection&lt;Enrollment&gt; Enrollments { get; set; }
        }

Is it not required anymore?

  [1]: https://stackoverflow.com/questions/25715474/why-navigation-properties-are-virtual-by-default-in-ef
  [2]: https://docs.microsoft.com/en-us/aspnet/core/data/ef-mvc/intro

Content Type	Original Author	Original Content on Stackoverflow
Question	Dismissile	View Question on Stackoverflow
Solution 1 - C#	RPM1984	View Answer on Stackoverflow
Solution 2 - C#	dav_i	View Answer on Stackoverflow

Entity Framework - Add Navigation Property Manually

C# Problem Overview

C# Solutions

Solution 1 - C#

Solution 2 - C#

LINQ Ring: Any() vs Contains() for Huge Collections

What exactly is node.js used for?

Attributions