! Operator (C# Reference)
The logical negation operator (!) is a unary operator that negates its operand. It is defined for bool and returns true if and only if its operand is false.
Remarks
User-defined types can overload the ! operator (see operator).
Example
class MainClass4
{
static void Main()
{
Console.WriteLine(!true);
Console.WriteLine(!false);
}
}
/*
Output:
False
True
*/