Dot Net Pulse: January 2008

Thursday, January 31, 2008

System.Reflection - MethodInfo class (usage)

A MethodInfo class provides detailed information about a single method of a class or an interface. The reflected method may be a static method or an instance method. The MethodInfoSpy example shows how to obtain the method information of a class including the access modifiers, type or input parameters:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Drawing;
using System.Reflection;

namespace MethodInfoSpy
{
    class Program
    {

        static void Main(string[] args)
        {
            Type type = typeof(Program);
            MethodInfo [] methodInfos = type.GetMethods();
            foreach (MethodInfo methodInfo in methodInfos)
            {
                // retrive method information
                Console.WriteLine("Name: {0}, Public: {1}, Is Static: {2}, Return Type: {3}",
                                    methodInfo.Name,
                                    methodInfo.IsPublic,
                                    methodInfo.IsStatic,
                                    methodInfo.ReturnType.FullName);

                // retrive method parameters information
                ParameterInfo [] paramInfos =  methodInfo.GetParameters();
                foreach (ParameterInfo paramInfo in paramInfos)
                {
                    Console.WriteLine("Parameter Name: {0}, Parameter Type: {1}",
                        paramInfo.Name, paramInfo.ParameterType.FullName);
                }
            }
            Console.ReadLine();
        }


        public void DoNothing()
        {
        }

        public int Add(int x, int y)
        {
            return x + y;
        }
    }
}

A sample of the output follows:

Name: DoNothing, Public: True, Is Static: False, Return Type: System.Void

Name: Add, Public: True, Is Static: False, Return Type: System.Int32

Parameter Name: x, Parameter Type: System.Int32

Parameter Name: y, Parameter Type: System.Int32

Name: GetType, Public: True, Is Static: False, Return Type: System.Type

Name: ToString, Public: True, Is Static: False, Return Type: System.String

Name: Equals, Public: True, Is Static: False, Return Type: System.Boolean

Parameter Name: obj, Parameter Type: System.Object

Name: GetHashCode, Public: True, Is Static: False, Return Type: System.Int32

Technorati Tags: c#,reflection

How to support != and == operations for C# struct

Sometimes we prefer to use structs instead classes .The C# is a convenient way to store coordinates ,complex number etc .
In an example below I'm presenting how to support == and != operators in case we want to check if our structs are equal.

// <summary>
/// Circle
/// </summary>
struct Circle
{
    public Point Center;
    public double Radius;

    /// <summary>
    /// Compares two Circle objects. The result specifies whether the values
    /// of the Center or Radius properties of the two Circle objects are equal.
    /// </summary>
    /// <param name="left">A Circle to compare.</param>
    /// <param name="right">A Circle to compare.</param>
    /// <returns>true if the the Center properties or the Radius properties 
    /// of left and right are equal; otherwise, false.</returns>
    public static bool operator ==(Circle left, Circle right)
    {
        return (left.Center == right.Center) && (left.Radius == right.Radius);
    }

    /// <summary>
    /// Compares two Circle objects. The result specifies whether the values
    /// of the Center or Radius properties of the two Circle objects are unequal.
    /// </summary>
    /// <param name="left">A Circle to compare.</param>
    /// <param name="right">A Circle to compare.</param>
    /// <returns>true if the values of either the Center properties 
    /// or the Radius properties of left and right differ; otherwise, false.</returns>
    public static bool operator !=(Circle left, Circle right)
    {
        return !(left == right);
    }


    /// <summary>
    /// Specifies whether this Circle contains the same Center and Radius as 
    /// the specified Object.
    /// </summary>
    /// <param name="obj">Another object to compare to.</param>
    /// <returns>
    /// true if obj is a Point and has the same Center and Radius as this Circle.
    /// </returns>
    public override bool Equals(object obj)
    {
        if (!(obj is Circle))
        {
            return false;
        }
        Circle circle = (Circle)obj;
        return (circle.Center == this.Center) && (circle.Radius == this.Radius);
    }

    /// .... You need to overload GetHashCode and ToString methods

}

Testing our struct ...

static void Main(string[] args)


   Circle circle1 = new Circle();
   circle1.Center = new Point(10, 10);
   circle1.Radius = 20;


   Circle circle2 = new Circle();
   circle2.Center = new Point(10, 10);
   circle2.Radius = 20;


   bool result = (circle1==circle2);
   Console.WriteLine("Is circle1 equal to circle2? [{0}]", result );

   circle2.Center = new Point(14, 10);
   result = (circle1 == circle2);
   Console.WriteLine("Is circle1 equal to circle2? [{0}]", result);

   Console.ReadLine();