Unable to update the EntitySet - because it has a DefiningQuery and no <UpdateFunction> element exist

It usually happens because one of the following reasons:

• Entity Set is mapped from Database view
• A custom Database query
• Database table doesn't have a primary key

After doing so, you may still need to update in the Entity Framework designer (or alternatively delete the entity and then add it) before you stop getting the error.

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>)

This is the case for me. Simply removing resulted in another error. I followed the steps of this post except the last one. For your convenience, I copied the 4 steps from the post that I followed to solve the problem as following:

1. Right click on the edmx file, select Open with, XML editor
2. Locate the entity in the edmx:StorageModels element
3. Remove the DefiningQuery entirely
4. Rename the store:Schema="dbo" to Schema="dbo" (otherwise, the code will generate an error saying the name is invalid)