C# CheckListBox - How to add object and have that object display text

Question

I want to have a number of objects that can be added to a checkedListBox in C# and have the objects be able to generate their own strings that are displayed in the list. I found an example of what I want to do in visual basic.

However, I can't figure out how to do it in c#. I've tried to implement my own class :

public class Device  {
    String s;

    public Device() {
        s = new String("test".ToCharArray());

    }

    public String toString() {
        return s;
    }
}

But when I run it, it displays "WindowsFormsApplication2.Device" in the list, not test..

Any suggestions would be appreciated.

Thanks, Reza

p.s. would it be possible to display text and a progress bar for each entry in a checklistbox?

You're p.s. is a whole other kind of problem, and warrants a question by it's self. here someone that tried something similar, have a look there. social.msdn.microsoft.com/Forums/en/winforms/thread/… — albertjan
– albertjan, Commented Sep 4, 2011 at 11:24

Ani · Accepted Answer · 2011-09-04 11:13:44Z

4

You are not correctly overriding the Object.ToString() virtual method:

The method-name is spelled incorrectly (C# is case-sensitive).
The override modifier on the method is missing; this is required when over-riding a virtual method.

Do it this way:

public override string ToString()
{
    return s;
}

answered Sep 4, 2011 at 11:13

Ani

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Comments

albertjan · Accepted Answer · 2011-09-04 11:15:03Z

1

make your toString method like this:

public override string ToString(){
    return s;
}

answered Sep 4, 2011 at 11:15

albertjan

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2 Comments

reza Over a year ago

I tried that, but it says 'no suitable method found to override'. I tried to subclass it as a String, but it didn't like that either.

albertjan Over a year ago

Note that ToString starts with a capital T.

Joaquim Rendeiro · Accepted Answer · 2011-09-04 11:20:18Z

1

the_ajp pointed correctly that the real problem is the camelCase toString when it should be PascalCase ToString.

public override String ToString() {
    return s;
}

Also, don't look at Java examples when coding C#, the s = new String("test".ToCharArray()); should be just s = "test";.

edited Sep 4, 2011 at 11:20

answered Sep 4, 2011 at 11:15

Joaquim Rendeiro

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2 Comments

albertjan Over a year ago

toString should be ToString from Object.ToString()

Joaquim Rendeiro Over a year ago

ohh you're so right hahah :) another reason not to look at Java examples when coding C#. I'm correcting my answer but upvoting yours.

Honza · Accepted Answer · 2011-09-04 12:44:40Z

0

You already have an answer, but here's a trick I like to use. The thing I don't like about using ToString() method on your model is that it mixes bussiness and view logic.

Instead, I create a wrapper class (Adapter design pattern), which keeps a reference to the model object and provides it own ToString method. You can combine this with anonymous functions to specify how exactly the displayed string should be obtained (you may want to display slightly different strings in different list boxes).

The wrapper class could look like this:

class ListBoxWrapper<T>
{
    private T obj;
    private Func<T, string> stringFunction;

    public ListBoxWrapper(T obj, Func<T, string> stringFunction)
    {
        this.obj = obj;
        this.stringFunction = stringFunction;
    }

    public override string ToString()
    {
        return stringFunction(obj);
    }
}

To simply use ToString() of the model, you can still do:

ListBox.Items.Add(new ListBoxWrapper<Device>(device, dev => dev.ToString()));

But you could also do (for example):

ListBox.Items.Add(new ListBoxWrapper<Device>(device, dev => dev.SerialNumber.ToString()));

To make this more useful, you can create your own class derived from ListBox or CheckedListBox, which will wrap your objects automatically. That way, you can also have the string function stored with the ListBox instead of with each individual item.

answered Sep 4, 2011 at 12:44

Honza

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2 Comments

user1195948 Over a year ago

To Honza, Can you provide a sample code since I really don't understand what you mean by: [To make this more useful, you can create your own class derived from ListBox or CheckedListBox, which will wrap your objects automatically. That way, you can also have the string function stored with the ListBox instead of with each individual item.] Thanks in advance, DH

Honza Over a year ago

Ok, quick answer. The code is for illustration only, I did not test, I only wrote it to explain what I meant. The simplest way to do it would be something like this: class CustomListBox<T> : ListBox { public Func<T, string> stringFunction { get; set; } public void addItem(T item) { this.Items.Add(new ListBoxWrapper<T>(item, stringFunction)); } }

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