The c# program I'm developing checks the first character of user input and if it starts with `.` (dot) I want to replace each character of user input with pacified character string while the user is writing, but I'm getting the error

> 
> Index out of bounds exception
> 
> 
> 

My code:

```
if (textBox1.Text.StartWith(".")) {
    string MyText = "Hello World";
    int x = 0;
    string NewText;
    while (x <= MyText.Length) {
        NewText = textBox1.Text.Replace(textBox1.Text[x], MyText[x]);
        TextBox1.Text = NewText;
        x++;
    }
}

```