Question

I’m using entity framework 4.1 and can’t add the connection on linqpad, it says that my child entity doesn’t have entity key defined. The message is: “Entity type “CashierPaymentType” has no key defined. Define the key for this entity type.”
I think this is happening when my child table has a composite key.
Example:

Table: Cashier
ID INT (Key)
Name VARCHAR(100)

Table: PaymentType
ID INT (Key)
Name VARCHAR(100)

// I think this is the problem!
Table: CashierPaymentType
CashierID INT (key) (foreign key)
PaymentTypeID INT (key) (foreign key)
Price SMALLMONEY

I’m using linqpad 4.35.1

Any help ?

Answer 1

The problem is that you’re telling LINQPad to new up your typed DbContext with a provider connection string instead of an Entity Framework connection string.

You’ll get the same error in Visual Studio if you construct your typed DbContext with a provider connection string.

A provider connection string is valid only if you’re doing code-first (in which case EF infers the model). In your case, the EDM is part of your project and is embedded in your assembly; therefore you must specify the full EF connection string as specified in your app.config so that EF can find it:

metadata=res://*/Model1.csdl|res://*/Model1.ssdl|res://*/Model1.msl;provider=System.Data.SqlClient;provider connection string="data source=.;initial catalog=TestDatabase;integrated security=True;multipleactiveresultsets=True;App=EntityFramework"

Another solution is to use the following connection string, which defers to the app.config file:

name=TestDatabaseEntities

If you do this in LINQPad, make sure you tell it where the app.config file lives, in the textbox provided.

A more subtle point is that the T4 file for your DbContext is different to the default that VS creates, in that your DbContext is missing the following code:

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
    throw new UnintentionalCodeFirstException();
}

If this override is present, it gives a more helpful error message if you specify the wrong kind of connection string.