文本框文字删除最后一个字符

Question

If the string is > 8, I need to remove the last character

How is this possible?

private void textBoxNewPassword_TextChanged(object sender, EventArgs e)
{
    if (textBoxNewPassword.TextLength == 9)
        textBoxNewPassword.Text = textBoxNewPassword.Text.Remove((textBoxNewPassword.Text.Length - 1), 1);
}

The code appears to do nothing.

Answer 1

Take an 8-character substring:

textBoxNewPassword.Text = textBoxNewPassword.Text.Substring(0, 8);

Better yet, set the MaxLength property on your TextBox to 8.

Answer 2

Use String.Substring Method (Int32, Int32) , where the first parameter is the starting index and 2nd parameter is the number of characters. Also if you need to check if the length is greater than 8 the do:

if (textBoxNewPassword.Text.Length > 8)
    textBoxNewPassword.Text = textBoxNewPassword.Text.SubString(0,8);

Answer 3

The spirit of your usage of Remove() is not improper, but you are forgetting that the first argument of Remove(int, int) is zero-based . Therefore, when you establish that in your if statement that the length is 9 ( TextBoxBase.TextLength simply overlays TextBoxBase.String.Length in most - but not all - cases), you are addressing the last character in your string when you Remove at position 8. Your code would have worked if you used instead:

textBoxNewPassword.Text = textBoxNewPassword.Text.Remove((textBoxNewPassword.Text.Length - 2), 1);

But I think everyone can agree that the Substring solution is cleaner and less brittle. I only mention this so we can understand why it was apparently doing nothing in the first place.

Answer 4

To do exactly as your question asks

    private void textBoxNewPassword_TextChanged(object sender, EventArgs e)
    {
        if (textBoxNewPassword.Text.Length > 8)
        {
            textBoxNewPassword.Text = textBoxNewPassword.Text.Substring(0, textBoxNewPassword.Text.Length - 1);
        }
    }

You said you only wanted to remove the last character if it's over a 8 characters long.

Answer 5

This is a possible generic solution.

static void Main(string[] args)
    {
        string text = "The max length is seven".RemoveChars(7);

    }

    public static string RemoveChars(this string text, int length)
    {
        if (!String.IsNullOrEmpty(text) && text.Length > length)
            text = text.Remove(length, text.Length - length);
        return text;
    }

Hope this help.