Question

🙂
I’m making a C# typing program
and I want the user to be unable to type anything when he types a wrong letter,
(I want the typing cursor to freeze at its position)
and when he presses backspace, only then he could resume his typing.

I have done this program in C++ by manipulating the ConsoleScreenCursorCoordinates,
I tried to do the same in C# via manipulating textBox.Location but it didn’t work.

In my program, there are 2 textBoxes, the sourceTextBox and the TypingTextBox
there is also a string variable called ‘text’ which will read from a textFile
via a StreamReader and then I use this text variable to compare each element from it with what the user is typing.

I tired this:

bool madeMistake = false;
Point CurrentTypingPosition;
string whatIsWrittenBeforeTheMistake = "";

private void TypingTextBox_KeyPress(object sender, KeyPressEventArgs e)
{
     try
     {
       if (!madeMistake)
       {
           if (e.KeyChar == text[typingIndex])
           {
               typingIndex++;
           }
           else if (e.KeyChar == backspace)
           {
               typingIndex--;
           }
           else
           {
               CurrentTypingPosition = TypingTextBox.Location;
               madeMistake = true;
               TypingTextBox.Text += " ";
               TypingTextBox.Location = CurrentTypingPosition;
               whatIsWrittenBeforeTheMistake = TypingTextBox.Text;
           }
       }
       else
       {

           if (e.KeyChar == backspace)
               madeMistake = false;
           else
           {
               TypingTextBox.Text = whatIsWrittenBeforeTheMistake;
               TypingTextBox.Location = CurrentTypingPosition;
           }
        }
     }
     catch (Exception ex)
     {
       MessageBox.Show(ex.Message);
     }
   }
}

Answer 1

Another variation on this is to use the Handled property of the KeyPress event args, so you get something like:

void textBox1_KeyPress(object sender, KeyPressEventArgs e)
{

    if (Char.IsControl(e.KeyChar))
    {
        e.Handled = false;
        return;
    }

    char expectedNext = expected[textBox1.SelectionStart];

    if (expectedNext != e.KeyChar)
    {
        e.Handled = true;
        Console.WriteLine("Incorrect input");
    }
}