c# 清空内容，例如ComboBox，TextBox

在清空窗体或者控件时，可以写成这样，例如：ctl.Text = ""; 但是这样会产生大量的冗余代码。可以写一个方法，批量清空；

例
/// <summary>
/// 清空/重置控件内容
/// </summary>
public void clear_from()
{
  foreach (Control ctl in gpbAddStu.Controls)
  {
    if (ctl is TextBox)
    {
       ctl.Text = string.Empty;
    }
    else if (ctl is DateTimePicker)
    {
       ctl.Text = DateTime.Now.ToString();
    }
    else if (ctl is ComboBox)
    {
      ComboBox com1 = ctl as ComboBox;
      com1.SelectedIndex = -1;
    }
    else if (ctl is PictureBox)
    {
      PictureBox ptb1 = ctl as PictureBox;
      ptb1.Image = null;
      ptb1.Refresh();
    }
    else if (ctl is RadioButton)
    {
       RadioButton rdb = ctl as RadioButton;
       rdb.Checked = false;
    }
  }
}