Custom combobox control

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I am trying to build a very simple custom ComboBox with a method accessibility(bool), which, with a true argument shows a dropdown list, and when false shows no dropdown, but displays a tooltip.

using System.Windows.Forms;

namespace Test
{
    public partial class ZComboBox : ComboBox
    {
        private object[] itemList;
        private ToolTip toolTip = new ToolTip();
        private string msg = "Message";
        public ZComboBox()
        {
            InitializeComponent();
        }
        public ZComboBox(object[] itemList)
        {
            InitializeComponent();
            this.itemList = itemList;
            Items.AddRange(itemList);
        }

        private AutoScaleMode _autoscaleMode = AutoScaleMode.Dpi;
        public AutoScaleMode AutoScaleMode
        {
            get { return _autoscaleMode; }
            set { _autoscaleMode = value; }
        }
        public void accessibility(bool accessible)
        {
            if (accessible)
            {
                Items.Clear();
                Items.AddRange(itemList);
                toolTip.SetToolTip(this, "");
            }
            else
            {
                Items.Clear();
                toolTip.SetToolTip(this, msg);
            }
        }
    }
}

In my form, I visually dropped in a couple of ZComboBox objects, zComboBox1 and zComboBox2. The form code is

using System.Windows.Forms;

namespace Test
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
            zComboBox1 = new ZComboBox(new object[] { "1", "2" });
            zComboBox1.accessibility(false);
            zComboBox2 = new ZComboBox(new object[] { "a", "b" });
            zComboBox2.accessibility(true); 
        }
    }
}

For a reason I cannot fathom, the controls are not showing any dropdown on accessibility(true), and don't have a tooltip on accessibility(false). Any help would be greatly appreciated.

What I have tried:

I have tried everything, but this eludes me.
It seems that the ZComboBox object I am modifying in the accessibility method is not the same one as is displayed on the form (the object with the same name).

Posted 5-Jan-21 12:44pm

hain

Updated 6-Jan-21 6:15am

v7

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Luc Pattyn · Answer 1 · 2021-01-05T14:34:00

Quote:
In my form I drop a couple of controls

isn't true.

What

zComboBox1 = new ZComboBox(new object[] { "1", "2" });

does is CREATE a ComboBox. It does not make it do anything, it does not make it part of your form; it will not show as you didn't add it to a collection of visible controls, e.g. that of your form. Try adding the line

this.Controls.Add(zComboBox1);

If WinForms is that new to you, I'd suggest you look inside the InitializeComponent method's code; that will show you how C# treats the controls you add with Visual Designer. When adding through your own code you basically need to do similar things.

BTW: your zComboBox1 variable isn't typed, does your code even compile?

BTW2: you also need to set a Location and maybe other properties (e.g. Font).

:)

Maciej Los · Answer 2 · 2021-01-06T00:22:00

This is not an answer, but a tip...

I would:
1. add private variable to return Accessibility

C#

private bool bAcc = false;

2. add Accessibility property

C#

public bool Accessibility => bAcc;

3. change accessibility method to SetAccessibility

C#

public void SetAccessibility(bool accessible)
{
    bAcc = accessible;
    if (bAcc)
    {
        Items.Clear();
        Items.AddRange(itemList);
        toolTip.SetToolTip(this, "");
    }
    else
    {
        Items.Clear();
        toolTip.SetToolTip(this, msg);
    }
}

4. and also add in constructor

C#

public ZComboBox(bool accessible)
{
    InitializeComponent();
    bAcc = accessible;
}

which will help you to create custom combobox with predefined Accessible property in code.

[EDIT]
Another tip:
1. Change custom combobox properties (if you want)
2. Build project
3. Go to form design view,
4. Open Toolbox and drag & drop 2 zCombBox'es on that form,
5. Remove these lines from constructor:

C#

zComboBox1 = new ZComboBox(new object[] { "1", "2" });
zComboBox2 = new ZComboBox(new object[] { "a", "b" });

5. Use SetAccessibiity method (in form constructor) to change Accessibility property

C#

zComboBox1.SetAccessibility(false);
zComboBox2.SetAccessibility(true);

7. Run project (F5).

That's all!

Custom combobox control

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