//设置已选文本提示
private void TextBox_SelectionChanged(object sender, RoutedEventArgs e)
{
System.Windows.Controls.TextBox textBox = sender as System.Windows.Controls.TextBox;
int row = textBox.GetLineIndexFromCharacterIndex(textBox.CaretIndex);
int col = textBox.CaretIndex - textBox.GetCharacterIndexFromLineIndex(row);
txtStatus_row.Text = $"行：{ row + 1}";
txtStatus_col.Text = $"列：{ col + 1}";;
txtStatus_select.Text = "已选：" + textBox.SelectionLength;
}