Simple Winform program with delegate,Error in the invoke call in the last line.

Question

1.00/5 (1 vote)

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I got a compile error at the lsat line "The name "getPointer" does not exist in the current context"
Thanks in advance.

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
namespace Delagate01
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        public class clsMaths
        {
            public delegate int PointerMaths(int i, int y);
            public PointerMaths getPointer(int intoperation)
            {
                PointerMaths objpointer = null;
                if (intoperation == 1)
                {
                    objpointer = Add;
                }
                else if (intoperation == 2)
                {
                    objpointer = Sub;
                }
                else if (intoperation == 3)
                {
                    objpointer = Multi;
                }
                else if (intoperation == 4)
                {
                    objpointer = Div;
                }
                return objpointer;
            }
            private int Add(int i, int y)
            {
                return i + y;
            }
            private int Sub(int i, int y)
            {
                return i - y;
            }
            private int Multi(int i, int y)
            {
                return i * y;
            }
            private int Div(int i, int y)
            {
                return i / y;
            }
        }
        private void Evaluate_Click(object sender, EventArgs e)
        {
            string resText = "";
            int intNumber1 = int.Parse(number1.Text);
            int intNumber2 = int.Parse(number2.Text);
            int intOperation = int.Parse(request.Text);
                     
           // int intResult = objMath.getPointer(intOPeration).Invoke(intNumber1, intNumber2);
            int intResult = intNumber1 + intNumber2;
            resText = string.Format("{0}", intResult);
            this.result.Text = resText;
            MessageBox.Show(getPointer(intOperation).Invoke(intNumber1, intNumber2));
          
        }
       
    }
}

Posted 2-Mar-11 5:13am

ephibr

Updated 2-Mar-11 5:56am

v3

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Comments

R. Giskard Reventlov 2-Mar-11 11:19am

What's the error? Unlikely anyone will copy and paste your code and try to recreate the problem: you need to give full information.

Yusuf 2-Mar-11 11:40am

You need to provide textual description of your problem

2 solutions

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Olivier Levrey · Answer 1 · 2011-03-02T06:06:00

Solution 2

In addition to Henry's answer:

You are trying to call a method declared in a nested class (so not from the correct class). Just comment the class declaration:

namespace Delagate01
{
    ...
        //remove the class declaration
        //public class clsMaths
        //{
              //keep everything inside
              ...

        //remove the last curly brace
        //}
    ...
}

Now it should compile.
If you want to encapsulate your functions in another class, then you will need to make your functions static for example, or instanciate the class to access its methods.

Posted 2-Mar-11 6:06am

Olivier Levrey

Updated 2-Mar-11 6:08am

v2

Comments

Henry Minute 2-Mar-11 12:12pm

I didn't really examine the whole of the OPs code, just the last line, since that's where they said the error was.

Yours is a much more complete explanation.

Olivier Levrey 2-Mar-11 12:15pm

Well, not complete since I added something from yours!
Anyway, I think OP can fix everything now.

ephibr 2-Mar-11 12:26pm

Thanks a lot but now I have a compile error on "void"
In the line " private void Evaluate_Click(object sender, EventArgs e)"
Thank you.

Espen Harlinn 4-Mar-11 12:39pm

Good points, a 5 - should have been enough :D

Henry Minute · Answer 2 · 2011-03-02T05:55:00

Solution 1

Your getPointer method returns a PointerMaths object. MessageBox is expecting a string and so it complains.

You could try

C#

MessageBox.Show(getPointer(intOperation).Invoke(intNumber1, intNumber2).ToString());

Although you may get "WhateverTheNamespaceIs.PointerMaths" as the output if PointerMaths doesn'y have a ToString() override.

Posted 2-Mar-11 5:55am

Henry Minute

Comments

Olivier Levrey 2-Mar-11 12:10pm

This is correct, but this is not the only error. You may have a look to my answer.

ephibr 2-Mar-11 12:30pm

Thanks a lot but i still got the errot with "ToString()", I tried "Solution 1 and I have an error
at the line " private void Evaluate_Click(object sender, EventArgs e)" compile error on "void"

Henry Minute 2-Mar-11 13:54pm

What is the wording of the error? We are not mind readers you know.

ephibr 2-Mar-11 14:00pm

It OK now you were very helpfull
Thanks a lot