C#: should object variables be assigned to null?

Question

In C#, is it necessary to assign an object variable to null if you have finished using it, even when it will go out of scope anyway?

Answer 1

No. When it comes to local variables it makes no difference at all if you have a reference to the object or not, what matters is if the reference will be used or not.

Putting an extra null assignment in the code doesn't hurt performance much, and it doesn't affect memory management at all, but it will add unmotivated statements to the code that makes it less readable.

The garbage collector knows when the reference is used the last time in the code, so it can collect the object as soon as it's not needed any more.

Example:

{
  // Create an object
  StringBuilder b = new StringBuilder();
  b.Append("asdf");
  // Here is the last use of the object:
  string x = b.ToString();
  // From this point the object can be collected whenever the GC feels like it
  // If you assign a null reference to the variable here is irrelevant
  b = null;
}