我可以像在 VB 中一样在 C# 中为控件提供索引属性吗？

Question

I've found similar answers to my question before, but not quite to what I'm trying to do...

In Visual Basic (last I used it, in 06/07) there was an "Index" property you could assign to multiple controls with the same name. I used this primarily to loop through controls, ie:

For i = 1 to 500
    picSeat(i).Print "Hello"
Next i

Is there a way to do this in C#? I know there is a .IndexOf() , but would that really help for what I'm doing? I want to have multiple controls with the same name, just different index. If I'm not being clear, please ask, don't downvote .

EDIT: This is a Windows Form Application, and I'm using Visual Studio 2012. I am talking about controls, not arrays/lists; this was possible in VB and I was wondering if it was possible at all in C#. So I want to have, say, 30 seats in a theatre. I want to have each seat represented by a picturebox named "picSeat". VB would let me name several objects the exact same, and would assign a value to a control property "Index". That way, I could use the above loop to print "Hello" in every picture box with only 3 lines of code.

Answer 1

No, this feature does not exist in C#, and was never implemented in the transition from classic VB to VB.Net.

What I normally do instead is put each of the controls in question in a common parent container. The Form itself can work, but if you need to distinguish these from others of the same type a GroupBox or Panel control will work, too. Then, you access the controls like this:

foreach (var picBox in parentControl.Controls.OfType<PictureBox>())
{
   // do something with each picturebox
}

If you want to use a specific control, just write by name:

pictureBox6.SomeProperty = someValue;

If you need to change a specific control determined at run-time, normally this is in response to a user event:

void PictureBox_Click(object sender, EventArgs e)
{
    var picBox = sender As PictureBox;
    if (picBox == null) return;

    //picBox is now whichever box was clicked
    // (assuming you set all your pictureboxes to use this handler)
}

If you really really want the Control Arrays feature, you can do it by adding code to create the array to your form's Load event:

PictureBox[] pictureBoxes = Me.Controls.OfType<PictureBox>().ToArray();

Answer 2

Are we talking WinForms here? I'm not sure, but I don't think you can have multiple controls in winforms with same name. But I vaguely recall doing something similar and the solution was to name them Button_1, Button_2 etc. Then you can iterate through all controls and get your own index.

Beware though that if you want to instanciate a separate control for each seat in a theatre, you might run into some serious performance issues :) I've done something similar to that as well and ended up drawing the whole thing on a canvas and using mouse coordinates to handle the events correctly.

Answer 3

You may want to check out the Uid property of controls.

( http://msdn.microsoft.com/en-us/library/system.windows.uielement.uid(v=vs.110).aspx )

You can access Control through Uid property with the following

private static UIElement FindUid(this DependencyObject parent, string uid)
{
    var count = VisualTreeHelper.GetChildrenCount(parent);
    if (count == 0) return null;

    for (int i = 0; i < count; i++)
    {
        var el = VisualTreeHelper.GetChild(parent, i) as UIElement;
        if (el == null) continue;

        if (el.Uid == uid) return el;

        el = el.FindUid(uid);
        if (el != null) return el;
    }
    return null;
}

And simply use

var control = FindUid("someUid");

I copied code from this post

Answer 4

If you create an indexed dictionary of your user control, it will behave pretty much the same as in VB6, though you'll not see it on the VS C# GUI. You'll have to get around the placement issues manually. Still - and most importantly -, you'll be able to refer to any instance by the index.

The following example is for 3 pieces for clarity, but of course you could automate every step of the process with appropriate loops.

public partial class Form1 : Form
    {
    ...

        Dictionary<int, UserControl1> NameOfUserControlInstance = new Dictionary<int, UserControl1>()
        {
            { 1, new UserControl1 {}},
            { 2, new UserControl1 {}},
            { 3, new UserControl1 {}}
        };

        private void Form1_Load(object sender, EventArgs e)
        {

            NameOfUserControlInstance[1].Location = new System.Drawing.Point(0, 0);
            NameOfUserControlInstance[2].Location = new System.Drawing.Point(200, 0);
            NameOfUserControlInstance[3].Location = new System.Drawing.Point(400, 0);

            Controls.Add(NameOfUserControlInstance[1]);
            Controls.Add(NameOfUserControlInstance[2]);
            Controls.Add(NameOfUserControlInstance[3]);
        }

        ...

    }  

Answer 5

I like using Tags to apply any type of meta data about the controls

for (int i = 0; i< 10; ++i)
{
  Button button = new Button();
  button.Tag = i;
}