Question

I have a table with a column that has null values… when I try to query for records where that column IS NULL:

THIS WORKS:

        var list = from mt in db.MY_TABLE
                   where mt.PARENT_KEY == null
                   select new { mt.NAME };

THIS DOES NOT:

        int? id = null;
        var list = from mt in db.MY_TABLE
                   where mt.PARENT_KEY == id
                   select new { mt.NAME };

Why?

Answer 1

after some more googling, I found the answer:

ref #1

ref #2

int? id = null;
var list = from mt in db.MY_TABLE
           where object.Equals(mt.PARENT_KEY, id)  //use object.Equals for nullable field
           select new { mt.NAME };

This LINQ renders to SQL as follows:

((mt.PARENT_KEY IS NULL) AND (@id IS NULL)) 
OR ((mt.PARENT_KEY IS NOT NULL) AND (@id IS NOT NULL) AND (mt.PARENT_KEY = @id))