设置文本框插入符号的最后可能位置

Question

I have a textbox and a TextChanged event with it that, whenever a user types something, a backslash will automatically be added to the end of the textbox IF there isn't one already.

This works fine except, if the user places the cursor at the end of the textbox AFTER the backslash and types, it moves the backslash to the left, adds the new text, and then another backslash at the end.

For instance, user enters C and C\\ appears. Now, if they click after the \\ and type a , C\\a\\ appears, when what I want is just Ca\\ .

So I need a way to set the last position of the cursor in the textbox to right before the backslash, if the user tries to set it after the backslash.

Here's the code for the textchanged event:

private void batchRootFolderText_TextChanged(object sender, EventArgs e)
{
    if (!batchRootFolderText.Text.EndsWith("\\"))
    {
        batchRootFolderText.Text = batchRootFolderText.Text + "\\";
    }
} 

Answer 1

private void batchRootFolderText_TextChanged(object sender, EventArgs e){
    if (!batchRootFolderText.Text.EndsWith("\\")){
        String temp = batchRootFolderText.Text;
        temp = temp.Substring(0, MyString.Length - 1);
        batchRootFolderText.Text = temp + "\\";
    }
} 

Tried cutting the end of the string off then replacing it?

Answer 2

You can add a variable that will keep track of where the backslash is and "move" it to the end when required:

int backSlashIndex = -1;

private void batchRootFolderText_TextChanged(object sender, EventArgs e)
{
    if (!batchRootFolderText.Text.EndsWith("\\"))
    {
        if(backSlashIndex != -1)
        {
            var fullText = batchRootFolderText.Text;

            var beforeBackslashText = fullText.Substring(0, backSlashIndex);
            var afterBackslashText = fullText.Substring(backSlashIndex + 1, fullText.Length - beforeBackslashText.Length - 1);

            batchRootFolderText.Text = beforeBackslashText + afterBackslashText;
        }

        batchRootFolderText.Text = batchRootFolderText.Text + "\\";
        backSlashIndex = batchRootFolderText.Text.Length - 1;
    }
}

Remember to add handling for cases when characters are removed by a user or when a user types the backslash character by themselves.

Answer 3

You can set the cursor position with the SelectionStart property: https://msdn.microsoft.com/en-us/library/system.windows.controls.textbox.selectionstart(v=vs.110).aspx

In the SelectionChanged Event ( https://msdn.microsoft.com/en-us/library/system.windows.controls.primitives.textboxbase.selectionchanged(v=vs.110).aspx ) you can check, if the caret is at the end of the text and if the text ends with a backslash and adjust the position.

if (textBox.SelectionStart == textBox.Length - 1 && textBox.Text.EndsWith(@"\")
    textBox.SelectionStart = textBox.Length - 2;

This code should do the work.