Solving Unable to update the EntitySet 'TestInstanceName' because it has a DefiningQuery and no element exists in the element to support the current operation. Problem

Hello,

If you get this error while working with entity framework ...

"Unable to update the EntitySet 'TestInstanceName' because it has a DefiningQuery and no <DeleteFunction> element exists in the <ModificationFunctionMapping> element to support the current operation."

then there is only one thing that you are missing is "Primary Key" in database table  or you are not passing primary key value while updating your data.