How to implement a c# code if 2 interfaces has same methods

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C#

interface iSame
    {
        void Method();
    }
    interface iSame1
    {
        int Method();
    }

    public partial class Form1 : Form, iSame, iSame1
    {
        public Form1()
        {
            InitializeComponent();
        }

        public void Method()
        {
            MessageBox.Show("This is iSame");
        }

        public int Method()
        {
            MessageBox.Show("This is iSame");
            return 1;
       }

How can i implement a this application with same method names of different interfaces ?

SQL

This gives an error saying already Method is implemented. But if you remove the int Method then also it gives compilation error saying Error    2   'WindowsFormsApplication1.Form1' does not implement interface member 'WindowsFormsApplication1.iSame1.Method()'. 'WindowsFormsApplication1.Form1.Method()' cannot implement 'WindowsFormsApplication1.iSame1.Method()' because it does not have the matching return type of 'int'.  F:\C#\WindowsFormsApplication1\WindowsFormsApplication1\Form1.cs    22  26  WindowsFormsApplication1

If both Tests have the same signature, same return type but differ in the types of exceptions they throw, then the class implements only the one Test, but it must contain the exceptions both Test's

If arguments are different we can implement without any error.

Posted 26-Jun-14 2:44am

code4Better

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2 solutions

Solution 1

This code project article Interfaces in C# (For Beginners)[^] has a section on this very problem (look for "P13.cs" in the article)

Posted 26-Jun-14 2:47am

CHill60

Comments

code4Better 26-Jun-14 9:32am

Hi Chill, thank you for the answer. The link what you have provided has same interface methods with same return types where as in my case the return type of the interface methods are different. That is the reason i am geting error.Do you have any more input on this ??

Sergey Alexandrovich Kryukov 26-Jun-14 14:48pm

Not a very good article, I think (and it even violated good naming conventions :-); and it does not really points out what to use to solve the problem.
If you simply pointed out a chapter in original Microsoft documentation, it would be more useful.
Please see my answer.
—SA

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Sergey Alexandrovich Kryukov · Accepted Answer · 2014-06-26T08:43:00

First of all, the methods are not the same; they only have the same name and signature. Method identity is made of the combination of assembly/type/method, not just name. If an assembly is signed, it even makes each method world-unique, even if other methods have the same name/signature.

You simply need to write explicit interface implementations instead of implicit. Generally, the explicit provides many benefits over the implicit.

Here is how:

C#

interface IFirst { void Method(); }
interface ISecond { void Method(); }

class SomeClass: Form, IFirst, ISecond { // here is where the problem starts
    //this is how it is solved:
    void IFirst.Method() { /* ... */ }
    void ISecond.Method() { /* ... */ }
} //class SomeClass

// now, the instances:

SomeClass classInstance = new SomeClass();
// you cannot use IFirst or ISecond members without a type cast with this variable,
// which is good, because it provides proper isolation

IFirst classInstanceAsIFirst = classInstance; // can use IFirst members
ISecond classInstanceAsISecond = classInstance; // same runtime object, but now you can use ISecond members

I hope this is all clear.

See also this old but still fully valid MSDN article: http://msdn.microsoft.com/en-us/library/aa288461%28v=vs.71%29.aspx[^].

Most recent chapters in MSDN manual:
http://msdn.microsoft.com/en-us/library/ms173157.aspx[^],
http://msdn.microsoft.com/en-us/library/tx1s9z1w.aspx[^].

—SA