In C#, parameters can be passed either by value or by reference. Passing parameters by reference allows function members, methods, properties, indexers, operators, and constructors, to change the value of the parameters and have that change persist. To pass a parameter by reference, use the ref or out keyword. For simplicity, only the ref keyword is used in the examples in this topic. For more information about the difference between ref and out, see ref, out, and Passing Arrays Using ref and out. For example:

// Passing by value
static void Square(int x)
{
    // code...
}

// Passing by reference
static void Square(ref int x)
{
    // code...
}

This topic includes the following sections:

• Passing Value-Type Parameters

• Passing Reference-Type Parameters