How to check a var for null value?

.net, .net-4.0, c#, c#-4.0, petapoco

Solution

if (result == null || result.Count() == 0) {
    // Checks whether the entire result is null OR
    // contains no resulting records.
}

I think the problem is not in your check for `null`, because linq is lazy loading. Your error is in using the expression `db.SingleOrDefault<TdUsers>(getUserQuery);`.

`.Single<T>(expression)` does not return null - it errors if the result returns no values. `.SingleOrDefault<T>(expression)`, however, returns a null value if the expression results in no values - and therefore is best combined with an `if (result == null)` type check, as you're using here.

Problem

I am using PetaPoco Micro-ORM with C# 4.0. The code below retrieves a single row from the database: ``` var result = db.SingleOrDefault<TdUsers>(getUserQuery); ``` I would like to check whether or not the result contains any rows, and whether is null. What is the best way to do this?

Original source