Entity Framework throws exception - Network Related or instance-specific error occurred

Question

I've followed a tutorial in MVC 3, and done this:

Made 4 classes and a DBClass:
User [has a] List of Websites [has a] List of Pages [has a] List of Comments [each marked word is a class of its own].

Then, I made a class called UserDataBaseDB this way:

public partial class UserDataBaseDB : DbContext
    {
        public DbSet<User> Users { get; set; }

        public UserDataBaseDB()
            : base(@"UserDataBaseDB")
        {
            if (this.Database.Exists())
            {
                try
                {
                    this.Database.CompatibleWithModel(false);
                }
                catch (InvalidOperationException)
                {
                    this.Database.Delete();
                }
            }

            if (!this.Database.Exists())
            {
                this.Database.Create();
                Seed();
            }
        }

        private void Seed()
        {
            var Mark = new User();
            Mark.ID = 0;
            Mark.MD5Pass = "4297f44b13955235245b2497399d7a93";
            Mark.UserName = "Admin";

            var Troll = new Comment();
            Troll.CommentData = "Fake!";
            Troll.Writer = Mark;

            var Site = new Website();
            Site.Name = "Admin Site";

            Site.Pages.ElementAt(0).Data = "Awesome website!";
            Site.Pages.ElementAt(0).Comments.Add(Troll);

            Mark.Websites.Add(Site);

            Users.Add(Mark);
        }
        public static UserDataBaseDB Create()
        {
            return new UserDataBaseDB();
        }
        public User FindUserByID(int id)
        {
            return (from item in this.Users
                    where item.ID == id
                    select item).SingleOrDefault();
        }

Then I added the Controller and View, and navigated to http://localhost:40636/Main, and I saw this message:

A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: SQL Network Interfaces, error: 26 - Error Locating Server/Instance Specified)

Line 14:             : base(@"UserDataBaseDB")
Line 15:         {
Line 16:             **if (this.Database.Exists())**
Line 17:             {
Line 18:                 try

Letting the marked line be the red line.

I've tried to re-install Entity Framework, also trying EFCodeFirst, tried making my own SqlDataBase and giving it the connection string, but nothing worked.

Does anyone know what's the solution? Thank you!

PS: I'm using VS Ultimate SP1 on a Win7 64bit machine.

What's your connection string? Does your work station able to connect to the sql server? — ysrb
– ysrb, Commented Oct 15, 2011 at 23:46

Adam Tuliper · Accepted Answer · 2011-10-16 01:02:08Z

This is likely a connect string issue, however I do see that you are trying to seed information and fully use the context in the constructor, which I would highly recommend you dont do. You can implement the OnModelCreating method and attempt your initialization code there, or even better in your application start. It just doesnt seem right to be stuck in the constructor as initialization is just starting at this point.

Set a breakpoint on

 if (this.Database.Exists())

Does the error happen immediately after that line? If so, triple check your connect string. Do you have your code in one project, or broken out? Make sure you are checking the connect string in your root web project's web.config and not any component's app.config if you so happen to be using that design.

Each time you changes from code-first, etc did you change your connect string? A code-first connect string is named after your context class and is simple:


<add name="UserDataBaseDB" connectionString="Data Source=|DataDirectory|test.sdf" providerName="System.Data.SqlServerCe.4.0" /%gt;

That is of course using SQLCe4. Sql Server would be


<add name="UserDataBaseDB" providerName="System.Data.SqlClient" connectionString="Data Source=.\SQLEXPRESS;Initial Catalog=YourDbName;Integrated Security=True;Pooling=False" /%gt;

or for a db in app_Data


<add name="UserDataBaseDB" providerName="System.Data.SqlClient" connectionString="data source=.\SQLEXPRESS;Integrated Security=SSPI;AttachDBFilename=|DataDirectory|\YourDatabase.mdf;User Instance=true" /%gt;

Thank you, that worked. although I have another problem with reading from the website which I will post in another question.

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