Generated query for tinyint column introduces a CAST to int

If you use IList<T>.Contains with a List<byte> the Entity Framework won't cast.

List<byte> byteValue = new List<byte> { 6 };
var entityList = from r in rep.DataContext.FooTable
             where byteValue.Contains(r.TinyintColumn)
             select r;

I ran into the same problem and blogged about it.

The CAST will affect performance because indexes won't be used on TinyintColumn

This is combination of points 2 and 4 in "Ten Common SQL Programming Mistakes". CAST is a function on a column, and without it you'll have a datatype mismatch anyway

@p__linq__0 should be tinyint or explicitly CAST.

However, it could be LINQ doesn't like tinyint primary keys according to MS Connect and (SO) asp.net mvc linq sql problem

You could "byte" the bullet (sorry) and use smallint...

My colleague found very nice trick to overcome this issue on Entity Framework 4.0.
Works for smallint, I didn't try on tinyint.

Insteal of equals (==) - use Contains() operator which was implemented with EF 4.0.

For example:
say you have the column SmallIntColumn.

instead of:

short shortValue = 6;
var entityList = from r in rep.DataContext.FooTable
                 where r.SmallIntColumn == shortValue
                 select r;

use

short[] shortValue = new short[] { 6 };
var entityList = from r in rep.DataContext.FooTable
                 where shortValue.Contains(r.SmallIntColumn)
                 select r;

Check the SQL generated - it is now without the CAST!
And from my tests - the execution plan used my (filtered) index on the column just perfectly.

Hope it helped.
Shlomi