An extension method for checking if an object is null

NotNullExtension.cs

public static class NotNullExtension
{
    public static TResult IfNotNull<TSource, TResult>(this TSource source, Func<TSource, TResult> accessor, TResult @default = default(TResult))
        where TSource : class
    {
        return source != null
            ? accessor(source)
            : @default;
    }
}