DataSet ds = new DataSet();
MyClass.MyMethod( ds );

if (ds =!null)
{
    // Error message. Since ds is null.  But why the above ds =! null does not catch it? 
}

MyClass.MyMethod( DataSet ds)
{
     // for testing
     ds = null;
}

"The creative process is nothing but a series of crises." Isaac Bashevis Singer
"My experience is that as soon as people are old enough to know better, they don't know anything at all." Oscar Wilde
"If a nation values anything more than freedom, it will lose its freedom; and the irony of it is that if it is comfort or money that it values more, it will lose that too." W.Somerset Maugham