CSHARP

C# check control type

foreach(Control c in List)
{
  if (c is TextBox)
  {
    ((TextBox)c).Text = "This should be the new text";
  }
}

check control type in c#

foreach (Control c in panel.Controls)
    {
        if (c.GetType().Name == "TextBox")
        {
            c.Text = "";
        }
    }