! 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

// cs_operator_negation.cs
using System;
class MainClass 
{
    static void Main() 
{
        Console.WriteLine(!true);
        Console.WriteLine(!false);
    }
}

Output

False
True

See Also

Reference

C# Operators

Concepts

C# Programming Guide

Other Resources

C# Reference