Question

I have the following table:

create table tbl
(
    id int identity(1,1),
    val varchar(100)
)

Now when i use Entity Framework to map objects to this table, it works, however when i change the table definition as follows:

create table tbl1
(
    id int,
    val varchar(100)
)

Entity Framework does not maps objects to this table. Any clue as to why is this happening would be appreciated.

Answer 1

Entity Framework requires a Primary Key to generate a model from the database. If there is no Primary Key on a table it will simply select the non-nullable columns as a concatenated primary key and the Entity will be read/only.

In your first table identity definition makes your id column non-nullable so you were able to create an Entity. You should have seen this message while adding that table:

“The table/view ‘tbl1’ does not have a primary key defined. The key
has been inferred and the definition was created as a read-only
table/view.”

In your second table however there is no non-nullable column and EF cannot create an Entity for it. See the message when you try to add it:

“The table/view ‘tbl1’ does not have a primary key defined and no
valid primary key could be inferred. This table/view has been
excluded. To use the entity, you will need to review your schema, add
the correct keys, and uncomment it.”