Beginning C# 2008 Objects: From Concept to Code

15.2. C# Exception Handling

Exceptions are a way for the .NET runtime to signal that something has gone wrong during program execution—that something could potentially cause a program to abort. One such situation would be trying to access a nonexistent object, as in the following example:

Student s1 = new Student();
Student s2 = null;

s1.Name = "Fred";  // this line is fine
s2.Name = "Mary";  // this line throws an exception

Let's explore what is happening in the preceding code.

We declare two Student object references but only instantiate one Student object; s2 is assigned the value null, indicating that it isn't presently holding onto any object.

Student s1 = new Student();
Student s2 = null;

When we subsequently attempt to assign a value to ...