How to get row and column number in richtextbox?

Question

C++ / C#

How to get row and column number in richtextbox?
int i = richTextBox1.SelectionStart;
int line = richTextBox1.GetLineFromCharIndex(i);
label1.Text = line.ToString();
int fc = richTextBox1.GetFirstCharIndexFromLine(line);
int column = i - fc;
label2.Text = column.ToString();
it's not right here