Question

How come setting OrganizationName = null does not work? I am doing a union and would like to set the value to null.

from a in Activities
select new 
{
    a.ActivityID,
    a.ActivityName,
    a.OrganizationID,
    OrganizationName = null
}

Answer 1

You can’t actually do this:

It is a compile-time error for an
expression in an anonymous object
initializer to be of the null type.

However, you can do this:

from a in Activities 
select new  
 { 
  a.ActivityID, 
  a.ActivityName, 
  a.OrganizationID, 
  OrganizationName = (object)null 
 } 

This is because in an anonymous object it needs to be able to determine the type of that variable, and it doesn’t want to assume it is just object. In fact for your example you may not even want that (you might want a string or a complex type e.g. Organisation). This is the same problem as going:

var a = null; /* What am I oh cruel world */

Having said that I can’t see the utility of what you’re trying to do here so perhaps if you elaborate on your use-case a more useful answer may be found.

References:

• C# Version 3.0 Specification
• Relevant article