Two errors I need help with.

Question

Error1:

  foreach (System.Windows.Forms.Button b in this.Controls)
                             {
                                 b.Image = WindowsApp1.Properties.Resources.BtnImg;
                               }

Unable to cast object of type 'System.Windows.Forms.GroupBox' to type 'System.Windows.Forms.Button'.

Error2:

String temp = ListBox1.Items[0].ToString

Cannot convert method group 'ToString' to non-delegate type 'string'. Did you intend to invoke the method?