assets/samples/Samples/AppearanceAssetEditing/CS/Request.cs

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using System.Threading;

namespace Revit.SDK.Samples.AppearanceAssetEditing.CS
{  /// <summary>
   ///   A list of requests the dialog has available
   /// </summary>
   /// 
   public enum RequestId : int
   {
      /// <summary>
      /// None
      /// </summary>
      None = 0,
      /// <summary>
      /// "Select" request
      /// </summary>
      Select = 1,
      /// <summary>
      /// "Lighter" request
      /// </summary>
      Lighter = 2,
      /// <summary>
      /// "Darker" request
      /// </summary>
      Darker = 3
   }         

   /// <summary>
   ///   A class around a variable holding the current request.
   /// </summary>
   /// <remarks>
   ///   Access to it is made thread-safe, even though we don't necessarily
   ///   need it if we always disable the dialog between individual requests.
   /// </remarks>
   /// 
   public class Request
   {
      // Storing the value as a plain Int makes using the interlocking mechanism simpler
      private int m_request = (int)RequestId.None;

      /// <summary>
      ///   Take - The Idling handler calls this to obtain the latest request. 
      /// </summary>
      /// <remarks>
      ///   This is not a getter! It takes the request and replaces it
      ///   with 'None' to indicate that the request has been "passed on".
      /// </remarks>
      /// 
      public RequestId Take()
      {
         return (RequestId)Interlocked.Exchange(ref m_request, (int)RequestId.None);
      }

      /// <summary>
      ///   Make - The Dialog calls this when the user presses a command button there. 
      /// </summary>
      /// <remarks>
      ///   It replaces any older request previously made.
      /// </remarks>
      /// 
      public void Make(RequestId request)
      {
         Interlocked.Exchange(ref m_request, (int)request);
      }
   }
}