Question

I am learning the C# programming language and am making a payroll application add-on for SAP business One. I have built a customized calculator that has various commands, adding, subtracting etc. I am using Visual Studio 2010.

The output “screen” is a rich textbox named ‘formula_display’.

I am able to input numbers and commands and they show properly on the formula_display from left to right i.e, 2 8 9 * <= etc

I also have input buttons for operands e.g (), <>, [] and {}

My problem:

If I type, 4 * () and then try to input some number, e.g 9 inside the brackets (by clicking inside the () in order to place the cursor there), I’m unable to do so because the the number will appear after the bracket, i.e 4 * ()9.

How do I modify my code to be able to fix the problem:

Code Snippet:

private void btn9_Click(object sender, EventArgs e)
    {
        if (inputStatus)
        {
            formula_display.Text += btn9.Text;
        }
        else
        {
            formula_display.Text = btn9.Text;
            inputStatus = true;
        }
    }

Any help appreciated. I am using Windows Forms

Answer 1

Try something like this in WPF:

formula_display.SelectionLength = 0;
formula_display.Text.Insert(formula_display.CaretIndex, btn9.Text);

and something like this in WinForms:

formula_display.SelectionLength = 0;
formula_display.Text.Insert(formula_display.SelectionStart, btn9.Text);