如何取消选中 C# 中的单选按钮，同时仍然只允许第一个单选按钮可选项卡？

Question

Not sure if the title makes much sense, so here is the full context:

I'm coding in C#. I've made an app with several UserControls, each one with many textboxes and radiobuttons. All radiobuttons are placed in a panel in a set of 2, looking like this:

[ <label> O <radiobutton1text> O <radiobutton2text> ]

(while the first radiobutton have TabStop = true, and the second's TabStop = false)

When tabbing to such panel, only radiobutton1text is focused, and when hitting the LeftArrow key the radiobutton2text is selected. That's the desired outcome.

In order to make a UserControl load faster the second (and above) time, I'm not closing it but rather replacing it with a different UserControl each time the contents need to change. But this rises an issue: When UserControl X is open, then on top of it I open UserControl Y and then back to X, the textboxes and radiobuttons still have the contents from the first session of when I had UserControl X open for the first time. (I need the contents of textboxes and radiobuttons to be reset after replacing a UserControl).

So I made a function that loops through all controls and empties their contents. The problem is, when I uncheck the radiobuttons (and restore their TabStop state to true) in this function, the second radiobutton is tabbable after I check either one of them and then invoke the function, whereas it wasn't before going through this function.

The function:

        public void BackToMain(object sender, EventArgs e)
        {
            // Go through all controls and empty each TextBox, RichTextBox, RadioButton or ComboBox.
            int parentControlsCount = Controls.Count - 1;
            for (int i = parentControlsCount; i >= 0; i--)
            {
                if (Controls[i].HasChildren == true)
                {
                    int childrenControlsCount = Controls[i].Controls.Count - 1;
                    for (int j = childrenControlsCount; j >= 0; j--)
                    {
                        var controlType = Controls[i].Controls[j].GetType().ToString();

                        switch (controlType)
                        {
                            case "System.Windows.Forms.TextBox":
                            case "System.Windows.Forms.RichTextBox":
                                Controls[i].Controls[j].Text = null;
                                break;

                            case "System.Windows.Forms.RadioButton":
                                // Restore both properties to default value
                                ((RadioButton)Controls[i].Controls[j]).Checked = false;
                                if (j == 1)
                                    ((RadioButton)Controls[i].Controls[j]).TabStop = true;
                                else if (j == 2)
                                    ((RadioButton)Controls[i].Controls[j]).TabStop = false;
                                break;

                            case "System.Windows.Forms.ComboBox":
                                ((ComboBox)Controls[i].Controls[j]).SelectedIndex = -1;
                                break;
                        }
                    }
                }
            }
        }

What am I doing wrong?

Answer 1

I ended up applying this gross hack- a function on every second radiobutton's CheckedChange:

        private void DisableTabStopOnCheckedChange(object sender, EventArgs e)
        {
            // Assume the following STR:
            // 1. In any radiobutton panel, select any radiobutton (without ever invoking BackToMain function in the first post);
            // 2. Invoke the BackToMain function;
            // 3. In the same radiobutton panel as in step #1, click the second radiobutton.
            // Normally, without this function, if the user will now cycle through the controls using the Tab key, both the first and second radiobuttons will be tabbable,
            // and that's because in the BackToMain function we reset their Checked and TabStop properies, and that's something that should be handled automatically by the control itself.
            // Doing it manually means that for the *first time* selecting the second radiobutton, the first one's TabStop state won't update, which means both radiobuttons
            // will have the TabStop state set to true, causing both to be tabbable.
            // This is a gross hack to fix this by disabling TabStop on the first radio button if the second one is checked and the first one's TabStop state
            // is true (this should happen only after BackToMain has been invoked).
            if (((RadioButton)sender).Checked)
            {
                var firstRadioButton = ((RadioButton)sender).Parent.Controls[1];
                if (((RadioButton)firstRadioButton).TabStop == true)
                {
                    ((RadioButton)firstRadioButton).TabStop = false;
                }
            }
        }

Not a pretty solution, I know. But it works.