Interface

A simple example for interface

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

namespace WindowsFormsApplication4
{
    class Factory
    {
        public static ITest create(int itype) // return a ITest(interface) Type. This interface can be used to save the return method.
        {
            if (itype == 1)
            {
                return new Test();
            }
            else if (itype == 2)
            {
                return new Test2();
            }
            else if (itype == 3)
            {
                return new Test3();
            }
            else
            {
                return new Test4();
            }
        }
    }
}

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

namespace WindowsFormsApplication4
{
    interface ITest
    {
        // This interface class collects the same method(s) from Test.cs, Test2.cs, Test3.cs and Test4.cs.
        // So that we can modify these classes through modify the methods in these classes.
        string iText();
        //  string iText2();
    }
}

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

namespace WindowsFormsApplication4
{
    class Test : ITest
    {
        #region ITest Members

        public string iText()
        {
            // TODO:  Add Test.printText implementation
            return ("Test string.");
        }
        //public void testmethod()
        //{
        //    int aaa;
        //}
        #endregion
    }
}

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

namespace WindowsFormsApplication4
{
    class Test2 : ITest
    {
        #region ITest Members

        public string iText()
        {
            // TODO:  Add Test.printText implementation
            return ("Test2 string.");
        }
        //public void testmethod1()
        //{
        //    int aaa;
        //}

        #endregion

    }
}

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

namespace WindowsFormsApplication4
{
    class Test3 : ITest
    {
        #region ITest Members

        public string iText()
        {
            // TODO:  Add Test.printText implementation
            return ("Test3 string.");
        }
       
        #endregion

    }
}

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

namespace WindowsFormsApplication4
{
    class Test4 : ITest
    {
        #region ITest Members

        public string iText()
        {
            // TODO:  Add Test.printText implementation
            return ("Test4 string.");
        }
        //public void testmethod4()
        //{
        //    int aaa;
        //}
        #endregion
    }
}

     private void button1_Click(object sender, EventArgs e)
        {
            ITest it; // We define a interface function it.
            it = Factory.create(4); // Return a interface function, after Factory.create.
            this.label1.Text = it.iText(); // Directly use the interface function "it", just like Test4.iText();
        }