Coordinates of Caret in richtextbox C#

Griff's Answer is correct, but only for WPF.

For System.Windows.Forms it is more tricky. The position in text is defined by System.Windows.Forms.RichTextBox.SelectionStart. This is a character index. You probably need a line number and position in line. For this purpose, first use GetLineFromCharIndex; it will give you the line. When you know the line, use GetFirstCharIndexFromLine to get the character index again. The difference between your original character index and the character index at the beginning of the line will calculate the position in the line, that is, a column. See other System.Windows.Forms.RichTextBox.Get... methods for more information.

In addition to Griff's Answer: for WPF, CaretPosition will return an instance of TextPointer. Use this class to find out the line and position in line.

—SA