C# Primitive Type	BCL Type	Description
sbyte	System.SByte	Signed 8-bit value
byte	System.Byte	Unsigned 8-bit value
short	System.Int16	Signed 16-bit value
ushort	System.UInt16	Unsigned 16-bit value
int	System.Int32	Signed 32-bit value
uint	System.UInt32	Unsigned 32-bit value
long	System.Int64	Signed 64-bit value
ulong	System.UInt64	Unsigned 64-bit value
char	System.Char	16-bit Unicode character
float	System.Single	IEEE 32-bit float
double	System.Double	IEEE 64-bit float
bool	System.Boolean	A True/False value
decimal	System.Decimal	96-bit signed integer times 100 through 1028 (common for financial calculations where rounding errors can't be tolerated)
object	System.Object	Base of all types
string	System.String	String type

// Reference Type (because of 'class')
class  RectRef { public int x, y, cx, cy; }

// Value type (because of 'struct')
struct RectVal { public int x, y, cx, cy; }

static void SomeMethod {
   RectRef rr1 = new RectRef();  // Allocated in heap
   RectVal rv1;                  // Allocated on stack (new optional)
   rr1.x = 10;                   // Pointer dereference
   rv1.x = 10;                   // Changed on stack

   RectRef rr2 = rr1;            // Copies pointer only
   RectVal rv2 = rv1;            // Allocate on stack & copies members
   rr1.x = 20;                   // Changes rr1 and rr2
   rv1.x = 20;                   // Changes rv1, not rv2
}

// Declare a value type
struct Point {
   public int x, y;
}

static void Main() {
   ArrayList a = new ArrayList();
   for (int i = 0; i < 10; i++) {
      Point p;                // Allocate a Point (not in the heap)
      p.x = p.y = i;          // Initialize the members in the value type
      a.Add(p);               // Box the value type and add the
                              // reference to the array
   }
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}

public static void Main() {
   Int32 v = 5;             // Create an unboxed value type variable

   // When compiling the following line, v is boxed 3 times
   // wasting heap memory and CPU time
   Console.WriteLine(v + ", " + v + ", " + v);

   // The lines below use less memory and run faster
   Object o = v;           // Manually box v (just once)

   // No boxing occurs to compile the following line
   Console.WriteLine(o + ", " + o + ", " + o);
}