(C#) Getting the index from a remove char of a TextBox WinForms

Question

I have a TextBox where the user can add and remove text, however each char relates to a row on a DataGridView, with a variety of user-selectable options. So knowing what char is being removed is very important because the DataGridView needs to know what row must be removed.

At first, I had a simple string-compare method, but with duplicate char sequences (ei "aaaa") it couldn't figure out which letter was removed and defaulted to returning the index of last char in the sequence. So I went online to see if there was a way to track the text caret's position, and there is...but not for WinForms. The only aspects I found for the Caret was SelectionStart , SelectionLength and SelectionText ; which will be usefully for batch remove, but not when the user hits the backbutton/deletebutton.

I'm pretty stumped right now. The "easiest" solution is switching to XAML because it tracks the Caret Position... but that feels like quiter talk. Though with that said, I still have no idea how to tackle this problem... any suggestions? (─‿‿─;;)

Answer 1

You can try to define the variable originalText to save origianl textbox text and textlength to save text length.

Subscribe to textBox1_Enter to give them the initial value.

private void textBox1_Enter(object sender, EventArgs e)
{
    textlength = textBox1.Text.Length;
    originalText = textBox1.Text;
}

Then subscribe to textBox1_TextChanged to get the deleted chars .

int textlength;
string originalText;

private void textBox1_TextChanged(object sender, EventArgs e)
{
    if (textlength > textBox1.Text.Length)
    {
        Console.WriteLine($"You deleted the char from {textBox1.SelectionStart} to {textBox1.SelectionStart + textlength - textBox1.Text.Length - 1}");
        Console.WriteLine($"deleted substring {originalText.Substring(textBox1.SelectionStart, textlength - textBox1.Text.Length)}");
    }
    // reset
    textlength = textBox1.Text.Length;
    originalText = textBox1.Text;
}