Question

I have a method returning IEnumerable object, but I found that sometimes (on error) the method returns null value of IEnumerable.

The method looks something like this.

IEnumerable<string> function(String param1, String param2)
{
    IEnumerable s = null;

    s = (some query over here);

    return s;
}

When I call this method with param2, the function internally fails and returns s which is null at this time.

So, to detect this I used,

 IEnumerable<string> a = function(1,0);
 if (a.count<string> > 0) //not working
 if (a == 0)  //not working.

What is the correct method to use IEnumerable and check whether it is null before any other operation?

Answer 1

Yours s = (some query over here); is returning null. That is why you are getting the exception.

Later your check should be:

if(a != null)

and

if(a.Count() > 0)

You can combine both as:

if(a!=null && a.Count() >0)
{
 // do your work
}