使用专门命名的项目设计一个for循环

Question

I often run into this situation when writing code for a GUI and would like to know would be a best-practice way of solving this. The situation is this:

I have a number of identical items on my GUI which have different variable names, ie I have 10 'identical' buttons which are named Button1, Button2, Button3, etc...

The buttons' displayed text is updated in the code and I want to check when they are updated if they meet a certain condition and then change the text color based on that condition. So for button1 I would write:

if (Button1.text == "true"){
    Button1.textcolor = blue}
else if (Button1.text == "false"){
    Button1.textcolor = red}

Now it seems redundant to have to write this code again for each of the 10 buttons, replacing Button1's variable name with Button2's and so on up until Button10. Is there a way to change the "Button1" part of the code in a loop and keep everything else the same? So a pseudo-code example of what I'm looking for would be:

for (all buttons in (button1-button10)){
    if (thisbutton.text == "true"){
        thisbutton.textcolor = blue}
    else if (thisbutton.text == "false"){
        thisbutton.textcolor = red}}

I don't know how to best approach this scenario and would appreciate input and guidance on this.

Thanks

Answer 1

Whenever you have a set of similar objects don´t create a variable for every instance of those objects, instead put them into one single collection. Then you can easily loop this list and manipulate the objects within it:

var buttons = new List<Button>();

// put the buttons into the list using buttons.Add

for (var b in buttons)
{
    if (b.text == "true")
    {
        b.textcolor = blue
    }
    else 
    {
        b.textcolor = red
    }
}

You can also use a GridView to put all those buttons into a ragular grid.

Answer 2

Create your own button.

using System.Windows.Forms;
using System.Drawing;

namespace TestApp
{
    public class TheButton : Button
    {
        public void ChangeColor()
        {
            ForeColor = (Text == "true")  ? Color.Blue : Color.Red ;

        }
    }
}

Rebuild your solution, and you should see TheButton in the toolbox, in your form, Add a container class, like a panel, and add your instances of TheButton class.

You could then write a method, like:

    private void ChangeAllButtons()
    {
        foreach (var control in panel1.Controls.Cast<object>().Where(control => (control as TheButton) != null))
        {
            (control as TheButton).ChangeColor();
        }
    }

You will have to decide the best place to call ChangeAllButtons().

Answer 3

There are many ways to approach this.

As the buttons are created by the designer as fields of the window/panel, to list them you have to analyse the WPF tree (or use reflection on the main window panel which it's not really elegant).

To get all the Button children you can use this method:

public static IEnumerable<T> EnumVisualOfType<T>(Visual visual) where T : Visual
{
    for (var i = 0; i < VisualTreeHelper.GetChildrenCount(visual); i++)
    {
        var visualChild = (Visual)VisualTreeHelper.GetChild(visual, i);

        foreach (var child in EnumVisualOfType<T>(visualChild))
            yield return child;

        var childVisual = visualChild as T;

        if (childVisual != null)
            yield return childVisual;
    }
}

And then invoke it:

var allButtons = EnumVisualOfType<Button>(window).ToList();

And you have the list of all the buttons (which you can, of course, filter on a specific property if you like) and you can write your code once and use it in a foreach loop.

You can also explicitly add all your buttons to a list when the panel is created, but then you will have to remember to add them manually every time you create a new one.