EF Table per Hierarchy (TPH) not saving because can't insert value null in Discriminator column

I have a table used for multiply type of category and it contains a Discriminator column named 'ClassName' to specify the type of object t开发者_如何学Pythono load. The ClassName column is non nullable with a default value of 'Category'

My problem is when saving a new item , I get the error : 'Cannot insert the value null into column ClassName' table Category.

I tought that ef would set the ClassName value base on the new object class. How can I save my object with the right 'ClassName' value ?

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I changed my db Structure to accept null. EF will set null if the object name match the table name and will set the discreminator name for the derived classes.

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It's old question but I just met it today. In .net 4.0 code first I don't meet "disclaimer column" but when downgrade to net 3.5, it make me tired for a day. This is my solution

Change the column in the database to ALLOW NULL (using alter table) and update the edmx file to make it update the change(allow null)