Strategy Pattern VS Static Class

Question

need someone professional help me get the difference beteen
first :
static class SimpleMathOperations
{
public static double add( double a, double b) { return a + b; }
public static double subtract( double a, double b) { return a - b; }
public static double multiply( double a, double b) { return a * b; }
public static double divide( double a, double b) { return a / b; } }
second : Implementing the strategy pattern
public interface IMathOperation { double PerformOperation( double A, double B); }
// ADD -----------------------------------------------
class AddOperation: IMathOperation
{
#region IMathOperation Members
public double PerformOperation( double A, double B)
{ return A + B; }
#endregion }
// Subtract -----------------------------------------------
class SubtractOperation: IMathOperation
{
#region IMathOperation Members
public double PerformOperation( double A, double B)
{ return A - B; }
#endregion }
// MULTILPY -----------------------------------------------
class MultiplyOperation: IMathOperation
{
#region IMathOperation Members public double PerformOperation( double A, double B) { return A * B; }
#endregion }
// DIVIDE -----------------------------------------------
class DivideOperation: IMathOperation
{ #region IMathOperation Members public double PerformOperation( double A, double B) { return A/B; } #endregion }
I quoted strategy pattern from this website
http://www.c-sharpcorner.com/UploadFile/rmcochran/strategyPattern08072006095804AM/strategyPattern.aspx [ ^ ]

Vulpes · Answer

Well, the strategy pattern in this case seems both long-winded and counter-intuitive, so I'd stick with the static class.

Mohammed Mostafa · Answer

so I don't need to implement the strategy pattern ???? because the static method give me the same result
thx 4 ur reply

Vulpes · Answer

Well, in the first case you just have a static class which has four methods which perform the basic operations on doubles: add, subtract, multiply and divide.
To call one of these you simply do:
double a =  3.5;
double b  = 2.5;
double c = SimpleMathOperations.add(a, b);
Console.WriteLine(c); // 6
In the second case you have an interface which has a single method, PerformOperation, which performs a binary operation on doubles.
To cater for all 4 basic operations, you need to define four classes which implement this interface in the appropriate ways.
For example:
AddOperation addop = new AddOperation();
double a =  3.5;
double b  = 2.5;
double c = addop.PerformOperation(a, b);
Console.WriteLine(c); // 6