public static void InsertText(this System.Windows.Controls.TextBox textbox, string sTextToInsert) { int iCaretIndex = textbox.CaretIndex; int iOriginalSelectionLength = textbox.SelectionLength; string sOriginalContent = textbox.Text; textbox.SelectedText = sTextToInsert; if (iOriginalSelectionLength > 0) { textbox.SelectionLength = 0; } textbox.CaretIndex = iCaretIndex + 1; }