Question

I am new in c# development. I just trying to study the interface feature. Based on the articles and notes I read about interfaces, I tried to write a sample code to implement interface based on what I understood from those notes and articles.

But when I debugging the project I got a build error

“Inconsistent accessibility: parameter type ‘StartMachine’ is less accessible than method ‘SwitchBoard.switchPress(StartMachine)'”.

What is the problem here ?. or Did I implemented the interface in correct way ? or Is my concept about interface is wrong ?..

Please help.
Thanks in advance.

I posted my code below.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

public partial class _Default : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        StartMachine s1 = new Machine1();
        SwitchBoard switch1 = new SwitchBoard();
        switch1.switchPress(s1);
    }
}

interface StartMachine
{
    void startMachine();
}

public class Machine1 : StartMachine
{
    public void startMachine()
    {
        HttpContext.Current.Response.Write("Machine 1 Started");
    }
}

public class Machine2 : StartMachine
{
    public void startMachine()
    {
        HttpContext.Current.Response.Write("Machine 2 Started");
    }
}

public class SwitchBoard
{
    public void switchPress(StartMachine switchNum)
    {
        switchNum.startMachine();
    }
}

Answer 1

You need to put a public access modifier in front of your interface. The Machine1/2 classes are public, but your interface is defaulting to internal. This is less accessible than public.

Set interface to public access modifer:

public interface StartMachine {...}

Alternatively, you could change your classes to be:

internal class Machine1: StartMachine {...}
internal class Machine2: StartMachine {...}

For more information on access modifiers, take a look on MSDN.

Correction::

The Switchboard class and switchPress method are public. However, the switchPress method is attempting to access the StartMachine.startMachine (ugh, ambigious naming) method, which is internal (by default). You need to either change the StartMachine interface to be public, or change Switchboard/switchPress tointernal.