Operators and Expressions

Boolean Logical Operators

• Unary ! (logical negation) operator.

• Binary & (logical AND), | (logical OR), and ^ (logical exclusive OR) operators. Those operators always evaluate both operands.

• Binary && (conditional logical AND) and || (conditional logical OR) operators. Those operators evaluate the right-hand operand only if it's necessary.

For operands of the integral numeric types, the &, |, and ^ operators perform bitwise logical operations.

Logical negation operator !

bool passed = false;
Console.WriteLine(!passed);  // output: True
Console.WriteLine(!true);    // output: False

Logical AND operator &

bool SecondOperand()
{
    Console.WriteLine("Second operand is evaluated.");
    return true;
}

bool a = false & SecondOperand();
Console.WriteLine(a);
// Output:
// Second operand is evaluated.
// False

bool b = true & SecondOperand();
Console.WriteLine(b);
// Output:
// Second operand is evaluated.
// True

Logical OR operator |

bool SecondOperand()
{
    Console.WriteLine("Second operand is evaluated.");
    return true;
}

bool a = true | SecondOperand();
Console.WriteLine(a);
// Output:
// Second operand is evaluated.
// True

bool b = false | SecondOperand();
Console.WriteLine(b);
// Output:
// Second operand is evaluated.
// True

x	y	x&y	x|y
true	true	true	true
true	false	false	true
true	null	null	true
false	true	false	true
false	false	false	false
false	null	false	null
null	true	null	true
null	false	false	null
null	null	null	null

Logical exclusive OR operator ^

Console.WriteLine(false ^ false);  // output: False
Console.WriteLine(false ^ true);   // output: True
Console.WriteLine(true ^ false);   // output: True
Console.WriteLine(true ^ true);    // output: False

Conditional logical AND operator &&

bool SecondOperand()
{
    Console.WriteLine("Second operand is evaluated.");
    return true;
}

bool a = false && SecondOperand();
Console.WriteLine(a);
// Output:
// False

bool b = true && SecondOperand();
Console.WriteLine(b);
// Output:
// Second operand is evaluated.
// True

Conditional logical OR operator ||

bool SecondOperand()
{
    Console.WriteLine("Second operand is evaluated.");
    return true;
}

bool a = true || SecondOperand();
Console.WriteLine(a);
// Output:
// True

bool b = false || SecondOperand();
Console.WriteLine(b);
// Output:
// Second operand is evaluated.
// True

Operator Precedence
! > & > ^ > | > && > ||

null-coalescing operators (?? and ??=)