Can I create this type of event in C#?

Question

I have a List in my custom user control. I'd like the control to redraw the each Image in the List whenever the contents of that list is changed. Either a movement, addition or removal of an items should fire an event.

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Drawing;
using System.Data;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace WebServiceScanner
{
    public partial class imageList : UserControl
    {
        public imageList()
        {
            InitializeComponent();
        }

        public List<Image> Images { get; set; }

        public void AddImage(Image image)
        {
            Images.Add(image);
        }

        public void RemoveImage(Image image)
        {
            Images.Remove(image);
        }

        public void MoveImageLeft(int index)
        {
            Image tmpImage = Images[index];
            Images[index] = Images[index - 1];
            Images[index - 1] = tmpImage;
        }

        public void MoveImageLeft(int index)
        {
            Image tmpImage = Images[index];
            Images[index] = Images[index + 1];
            Images[index + 1] = tmpImage;
        }
    }
}

Can this be done?

Thanks for your guidance! Eager to learn!

score 4 · Accepted Answer · answered Nov 26 '10 at 23:49

4

You can use an ObservableCollection<T> instead of a List<T> and handle its CollectionChanged event.

answered Nov 26 '10 at 23:49

Frédéric Hamidi

258,201
41
486
479

Sounds exactly what I'm looking for! I'll try it out. – Nov 26 '10 at 23:53

score 0 · Answer 2 · answered Nov 26 '10 at 23:50

public partial class imageList : UserControl
    {

        public event OnChange;

        public imageList()
        {
            InitializeComponent();
        }

        public List<Image> Images { get; set; }

        public void AddImage(Image image)
        {
            Images.Add(image);
            this.OnChange();
        }

        public void RemoveImage(Image image)
        {
            Images.Remove(image);
            this.OnChange();
        }

        public void MoveImageLeft(int index)
        {
            Image tmpImage = Images[index];
            Images[index] = Images[index - 1];
            Images[index - 1] = tmpImage;
            this.OnChange();
        }

        public void MoveImageLeft(int index)
        {
            Image tmpImage = Images[index];
            Images[index] = Images[index + 1];
            Images[index + 1] = tmpImage;
            this.OnChange();
        }
    }

It may be advisable to also make the `Images` property read-only or private, unless it really _needs_ to be publicly settable. Otherwise it's possible to alter the list without calling the desired methods. — David, Nov 26 '10 at 23:52
it raises the onchange event which you can handle outside of the class — Ali Tarhini, Nov 26 '10 at 23:56

score 0 · Answer 3 · edited May 23 '17 at 10:26

0

You could also try using the BindingList. The differences are discussed in here: https://stackoverflow.com/questions/4284663/...

edited May 23 '17 at 10:26

Community

1
1

answered Nov 28 '10 at 01:52

Prasanna K Rao

1,086
2
8
18

Can I create this type of event in C#?

3 Answers3