It has a DefiningQuery but no InsertFunction element... err

Question

Well when a table is encountered without a PrimaryKey it is treated as a View.

And views show up in the EDMX file (open in an XML editor to see) in the StorageModel\EntitySet[n]\DefiningQuery element.

When you have a DefiningQuery the Entity becomes readonly unless you add modification functions. You need 3 modifications functions (aka Stored Procedures) one for each of Insert, Update and Delete.

But you have two options:

Change the key definion:

1. And convince the EF that what it thinks is a view is really a table
2. Or add the appropriate modification functions

In your case I recommend (1).

Just Add a primary key to the table. That's it. Problem solved.

ALTER TABLE <TABLE_NAME>
ADD CONSTRAINT <CONSTRAINT_NAME> PRIMARY KEY(<COLUMN_NAME>)

I was missing a primary key on my table and got this error message. One thing I noted was after I added the key to the table, I needed to clear the table from the edmx using the designer, save the edmx, then update it again to add the table back in. It wasn't picking up the key since it was already assigned as a view. This didn't require editing the edmx manually.

Add primary key to table, delete the model from the edmx model, then select update from database, build and run...... works

@Palantir. Verify that both of you tables have Primary Keys set, and be careful with multiple primary keys set in a table.