`NotImplementedException`

A C# NotImplementedException has been thrown. An exception's type helps us learn the reason the exception was thrown.

C# type notes

The NotImplementedException indicates in a clear way that the functionality being requested was simply not implemented.

Example

The NotImplementedException should not be thrown in completed programs. When adding a method, you may want the method to exist but you may not be able to implement it yet.

And This can help with a complex system as it is developed. This example uses NotImplementedException in an unimplemented method.

Detail The method signature returns an integer value. A compile-time error would occur if the method simply had a blank body.

Result The NotImplementedException prevents this from happening and so keeps the program compiling.

using System;

class Program
{
    static void Main()
    {
        Method();
    }

    static int Method()
    {
        // Leave this as a stub.
        throw new NotImplementedException();
    }
}Unhandled exception. System.NotImplementedException: The method or operation is not implemented.
   at Program.Method() in /home/sam/programs/consoletemp/Program.cs:line 13
   at Program.Main() in /home/sam/programs/consoletemp/Program.cs:line 7
Aborted (core dumped)

Self-documenting type

When using exceptions, you want to describe the problem as much as possible through the type itself. In error messages, the type of the exception is prominently featured.

Detail When the NotImplementedException occurs, you will realize that the problem is unfinished code—not another error.

Summary

As a descriptive exception type, the NotImplementedException is useful as a way to compile an unfinished program. Visual Studio inserts it in method stubs.