A value-type variable
contains its data directly as opposed to a reference-type variable,
which contains a reference to its data. Passing a value-type variable to a
method by value means passing a copy of the variable to the method. Any changes
to the parameter that take place inside the method have no affect on the
original data stored in the argument variable. If you want the called method to
change the value of the parameter, you must pass it by reference, using the ref or out keyword.
For simplicity, the following examples use ref.
,
delegate, dynamic,
interface, object,
string
C# Example
private void button1_Click(object sender, EventArgs e)
{
int i = 100;
PassByVal(i); // Don't
change original value
button1.Text = i.ToString(); // OutPut is : 100
PassByRef(ref i); // Change original value
button1.Text = i.ToString(); // OutPut is : 110
}
private void PassByRef(ref int i) { i += 10; }
private void PassByVal(int i) { i += 10; }
More Difference
Value Type
|
Reference Type
|
They are stored on stack
|
They are stored on heap
|
Contains actual value
|
Contains reference to a value
|
Cannot contain null values. However this can be achieved by nullable types
|
Can contain null values.
|
Value type is popped on its own from stack when they go out of scope.
|
Required garbage collector to free memory.
|
Memory is allocated at compile time
|
Memory is allocated at run time
|
