Why does not null in LINQ query still return null records? [closed]

Question

Why does the LINQ query return records that are null? I'm using the code below to no avail.

var list = (from t in dal.table
            where t.name != null);

Answer 1

You forgot to select.

var list = (from t in dal.table
            where t.name != null
            select t);

Answer 2

I encountered the same strange behavior. The C# code is

public DbSet<Document> Documents { get; set; }
List<Document> = Documents
    .Where(d => d.BusinessId = 818)
    .Where(d => d.CurrencyId != null)
    .ToList();

but the SQL statement generated is this:

exec sp_executesql N'SELECT 
[Extent1].[DocumentId] AS [DocumentId], 
[Extent1].[DateCreated] AS [DateCreated],
...
FROM [dbo].[Documents] AS [Extent1]
WHERE [Extent1].[BusinessId] = @p__linq__0',N'@p__linq__0 int',@p__linq__0=818    

Clearly LINQ ignores the .Where(d => d.CurrencyId != null) clause.

My solution was as follows:

List<Document> = Documents
    .Where(d => d.BusinessId = 818)
    .ToList() // <== Gel all documents and filter in memory
    .Where(d => d.CurrencyId != null)
    .ToList();

Note: Technically we move the NOT Null filter from Linq-To-Sql to Linq-To-objects.

Very inefficient since we select ALL the documents into memory and filter there (instead of filtering in the db-level).

I my case the number of records is usually small so the solution worked for me.

Answer 3

101 C# LINQ Examples: http://msdn.microsoft.com/en-us/vcsharp/aa336746