title: how to implement autoimplemented properties in C# for setting a value
body: <p>I am trying to use autoimplemented properties.
  It shows me error</p>
  
  <pre><code>    public OpenMode OpenFor
      {
          get;//must declare a body because it is not marked as abstract, partial or external. Why so 
          set
          {
              if (value == OpenMode.Add)
              {
                  btnAddGuest.Text = "Save";
                  btnUpdatePreference.Visible = false;
                  dgvGuestInfo.ClearSelection();
              }
              else if (value == OpenMode.Update)
              {
                  btnAddGuest.Text = "Update";
                  btnUpdatePreference.Visible = true;
              }
          }
      }
  </code></pre>