TextBox : Modify user's input

Question

When the user adds a ;, I want to add ; + Environment.NewLine in the TextBox.

I find this solution :

private void TextBox_OnPreviewTextInput(object sender, TextCompositionEventArgs e)
{
    if (e.Text == ";")
    {
        e.Handled = true;
        TextCompositionManager.StartComposition(
                new TextComposition(InputManager.Current,
                (IInputElement)sender,
                ";" + Environment.NewLine)
        );
    }
}

But after this, the undo don't work.

Can you explain me how control the user input and keep the undo stack?

Mohammad Haeri · Accepted Answer · 2018-09-05 00:33:30Z

2

-------------- Updated Code As Requested ---------

Use this Instead and 100% it's work. I test it for assurance.

private void TextBox_OnPreviewTextInput(object sender, TextCompositionEventArgs e)
{
    if (e.Text == ";")
    {
        // In this line remove preview event to  preventing event repeating
        ((TextBox)sender).PreviewTextInput -= TextBox_OnPreviewTextInput;

        // Whith this code get the current index of you Caret(wher you inputed your semicolon)
        int index = ((TextBox)sender).CaretIndex;

        // Now do The Job in the new way( As you asked)
        ((TextBox)sender).Text = ((TextBox)sender).Text.Insert(index, ";\r\n");

        // Give the Textbox preview Event again
        ((TextBox)sender).PreviewTextInput += TextBox_OnPreviewTextInput;

        // Put the focus on the current index of TextBox after semicolon and newline (Updated Code & I think more optimized code)
        ((TextBox)sender).Select(index + 3, 0);

        // Now enjoy your app
         e.Handled = true;
    }
}

Wish you bests , Heydar

edited Sep 5, 2018 at 0:33

answered Sep 4, 2018 at 22:11

Mohammad Haeri

1631 silver badge9 bronze badges

Sign up to request clarification or add additional context in comments.

4 Comments

vernou Over a year ago

Close, undo work with this solution. But when I press ';' in middle of sentence, ";\r\n" are put in the end.

Mohammad Haeri Over a year ago

I also Updated my asnwer as you asked, be suer to copying all of it. not part of it. I changed the Puting focus on last index too

Mohammad Haeri Over a year ago

I did not get your meaning by the word "dislike magic 3". Since we put 3 character to our text, so we must take 3 step forward till the caret travel to after semicolon. It's compeletly logical. Could you explain your meaning more?

vernou Over a year ago

The main goal of answer is being understandable/readable. Why I prefer ";\r\n".Length. When I read a answer, I don't want put effort to understand logic out of the problem. It's principally philosophical. ;)

vernou · Accepted Answer · 2019-11-29 08:40:26Z

1

Thank to Heydar for the solution. I applied some improvements :

private void TextBox_OnPreviewTextInput(object sender, TextCompositionEventArgs e)
{
    if (e.Text == ";")
    {
        var textBox = (TextBox) sender;
        var selectStart = textBox.SelectionStart;
        var insertedText = ";" + Environment.NewLine;

        // In this line remove preview event to  preventing event repeating
        textBox.PreviewTextInput -= TextBox_OnPreviewTextInput;

        // Now do The Job
        textBox.Text = textBox.Text.Insert(selectStart, insertedText);

        // Give the TextBox preview Event again
        textBox.PreviewTextInput += TextBox_OnPreviewTextInput;

        // Put the focus after the inserted text
        textBox.Select(selectStart + insertedText.Length, 0);

        // Now enjoy your app
        e.Handled = true;
    }
}

edited Nov 29, 2019 at 8:40

answered Sep 4, 2018 at 22:52

vernou

7,6825 gold badges40 silver badges74 bronze badges

2 Comments

Mohammad Haeri Over a year ago

Hi, Did you test it and does it work? See bro I done it more Direct and in less code with out safe case and with direct cast. Yes I accept that the safe cast is better for it safety , but direct cast is faster in writing and less in volume(The code I wrote is in just 6 line) and memory consuming and maybe faster in performance. Since you gonna use this event in TextBox event so the sender is not nothing else . it's just TextBox always, unless you add to an Other control.

vernou Over a year ago

This is an old proposal for improvement. You can ignore it. I edited the answer in this direction.

Collectives™ on Stack Overflow

TextBox : Modify user's input

2 Answers 2

-------------- Updated Code As Requested ---------

4 Comments

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

-------------- Updated Code As Requested ---------

4 Comments

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related