.NET 擴充實現代碼

class Command
{
public virtual void Execute() { }
}

class InvalidOperationException<T> : InvalidOperationException
where T : Command
{
public InvalidOperationException(string message) : base(message) { }
// some specific information about
// the command type T that threw this exception
}

static class CommandExtensions
{
public static void ThrowInvalidOperationException<TCommand>(
this TCommand command, string message)
where TCommand : Command
{
throw new InvalidOperationException<TCommand>(message);
}
}

class CopyCommand : Command
{
public override void Execute()
{
// after something went wrong:
this.ThrowInvalidOperationException("Something went wrong");
}
}

class CutCommand : Command
{
public override void Execute()
{
// after something went wrong:
this.ThrowInvalidOperationException("Something else went wrong");
}
}