C# TextBox Auto Caps Lock On

Question

I need the following code : When I press shift key then I write small letters in my TextBox in other case I write big letters something like a “reverse” or all time pressed Caps Lock Key. So This code and other similar is helpless because there are only one kind of letter size :

textBox1.CharacterCasing = CharacterCasing.Upper;
textBox1.CharacterCasing = CharacterCasing.Lower;

Thanks for help !

And why would you want to create a UI that confuses its users? — sticky bit, Jan 07 '20 at 21:34

score 0 · Answer 1 · answered Jan 07 '20 at 22:48

The easiest option is to change the text in the TextChanged event method. After entering a character, change its layout. But you must remember that text can be pasted / cut.

If you ignore this problem, you can use this simple example:

public partial class Form1 : Form
{
    int last_len = 0;
    bool char_to_lower = false;
    public Form1()
    {
        InitializeComponent();
    }

    private void textBox1_TextChanged(object sender, EventArgs e)
    {
        // save last cursor position
        var select_index = textBox1.SelectionStart;
        // if text not delete - change char casing
        if (textBox1.Text.Length > last_len && select_index > 0)
        {
            StringBuilder sb = new StringBuilder();
            sb.Append(textBox1.Text.Take(select_index - 1).ToArray());

            // check SHIFT and CAPS
            if (char_to_lower || Control.IsKeyLocked(Keys.CapsLock))
                sb.Append(textBox1.Text[select_index - 1].ToString().ToLower());
            else
                sb.Append(textBox1.Text[select_index - 1].ToString().ToUpper());

            sb.Append(textBox1.Text.Skip(select_index).ToArray());

            // insert new text in textBox
            textBox1.Text = sb.ToString();
            // return cursor position
            textBox1.SelectionStart = select_index;
        }
        // save last length
        last_len = textBox1.Text.Length;
    }

    private void textBox1_KeyDown(object sender, KeyEventArgs e)
    {
        if (e.KeyCode == Keys.ShiftKey || e.KeyCode == Keys.Shift) char_to_lower = true;
    }

    private void textBox1_KeyUp(object sender, KeyEventArgs e)
    {
        if (e.KeyCode == Keys.ShiftKey || e.KeyCode == Keys.Shift) char_to_lower = false;
    }
}

C# TextBox Auto Caps Lock On

1 Answers1