C# structure

Neo

Hi,

I just gone through following link

http://www.csharpfriends.com/Articles/getArticle.aspx?articleID=120

read following code lines. However following code is fine I guess because function MyMethod not initialise any variable. Although you declare MyInterface obj= new MyStruct(); still it will work. Please comment.

interface MyInterface
    {
         void MyMethod();
    }
    struct MyStruct : MyInterface
    {
        public  void MyMethod()
        {
            Console.WriteLine("Struct Method from MyStruct");
            Console.ReadLine();

        } 

    } // end of structure
    class Class1
    {
        /// 
        /// The main entry point for the application.
        /// 
        [STAThread]
        static void Main(string[] args)
        {
             MyInterface obj= new MyStruct();
                 
            obj.MyMethod(); // this is error
    
        }
    } // end of main class

2 Replies

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Neo18y ago
yeah it's polymorphism only; But I am jst wondered the one who posted this article made mistake he/she said error in code which is not true.
18y ago
When you create an instance of MyStruct and depose it as an instance of MyInterface, your simply exposing the members of MyInterface in the object you create, not MyStruct. I call it downcasting, because your casting a decendant class to a baser class.

However, obj.MyMethod() should work because its defined in the MyInterface interface. I just tested it and it worked in Visual Studio 2005.

I think this example shows another form of polymorphism if Im right... or may its composition, I cant remember :( Either way its an object oriented sample. Look at it this way:

Since MyStruct implements the interface MyInterface, it -IS- a MyInterface. Therefore it can be cast to type MyInterface :)