Code Injection works in C# too!

52 characters

}static Program(){System.Console.Write(0<1);for(;;);

so the whole thing becomes:

class Program
{
    static void Main()
    {
        System.Console.Write( "False" );
    }
    static Program()
    {
        System.Console.Write( 0 < 1 ); 
        for ( ; ; ) ;
    }
}

C#, 51 characters

Console.Write("\b\b\b\b\b");Console.Write("True ");

Will only work on standard output