Question

I’m having a heckuva time trying to match rows where a column is null. I know that in SQL, I have to use the IS keyword to find null columns:

SELECT * FROM Categories WHERE ParentCategoryID IS NULL;

I’m trying to recreate the above query in LINQtoSQL. I’ve tried:

var RootCats = categoriesRepository.Categories
    .Where(c => c.ParentCategoryID == null);

But this doesn’t return any records at all. I have found some posts that use a different syntax than what I’m used to in this post here. But I was having difficulty putting that principle into Lambda form.

How do I use LINQtoSQL and Lambda expressions to find rows with null columns?

Edit

Per question in the comments – ParentCategoryID is an int.

Answer 1

If the ParentCategoryID in your model isn’t nullable then it will get the default value of 0 and 0 != null. Open the designer and change the ParentCategoryID so that it is nullable.