Question

Hi we can not define in c# variable like this

if((var input = db.table.FirstOrDefault()) != null)
{
   // and here I could use my 'input' variable
}

but i can do it this way

for(var input = db.table.FirstOrDefault(); input != null; input = null)
{
  //opeartion

}

Can anyone tell me why? Woudn’t that be nice if we could do it using if ?

Answer 1

This is because writing

object input = db.table.FirstOrDefault();

is exactly the same like writing

object input; 
input = db.table.FirstOrDefault();

accoring to the C# specification.

This means that there is no any return value, so there is nothing to check !=null against.

Yes, I think it’s possible to trick this, to make some changes in compiler, but probabbly it doesn’t worth effort.