EF data model exclusion due to lack of primary key

It is common for some tables to lack primary keys when integrating existing databases into Entity Framework (EF) 4.0. This problem occurs when creating a new entity data model, causing an error message to indicate the missing primary key and then exclude the table.

It is generally believed that physical primary keys must be added to the affected table to resolve this issue. However, there is a workaround that allows you to use these tables without modifying their schema.

As Tillito suggests, this workaround involves modifying the SELECT statement of the problematic view in a new SELECT statement. This way you wrap the original SELECT statement, you can use the ISNULL function to specify the column to be used as the primary key. Instead, you can use the NULLIF function to prevent columns from being specified as primary keys.

Example:

Consider the following example:

SELECT
  ISNULL(MyPrimaryID,-999) MyPrimaryID,
  NULLIF(AnotherProperty,'') AnotherProperty
FROM ( ... ) AS temp

In this example, the ISNULL function forces EF to recognize "MyPrimaryID" as the primary key, while the NULLIF function ensures that "AnotherProperty" is not considered as the primary key.

By applying this technology, you can avoid the need to modify the database schema and seamlessly integrate existing tables into your EF data model, allowing data operations without the need to modify the physical primary key.