C＃傳遞額外的參數給事件

Question

我想通過三個額外的參數給事件：

geocodeService.GeocodeCompleted += new EventHandler<GeocodeService.GeocodeCompletedEventArgs>(geocodeService_GeocodeCompleted); 

的參數是

• int id
• string color

• double heading

  private void Geocode(string strAddress, int waypointIndex, int id, string color, double heading) 
  { 
  
  
      // Create the service variable and set the callback method using the GeocodeCompleted property. 
      GeocodeService.GeocodeServiceClient geocodeService = new GeocodeService.GeocodeServiceClient("BasicHttpBinding_IGeocodeService"); 
  
      // NEED TO PASS id, color, heading TO THIS EVENT HANDLER 
      geocodeService.GeocodeCompleted += new EventHandler<GeocodeService.GeocodeCompletedEventArgs>(geocodeService_GeocodeCompleted); 
  
      GeocodeService.GeocodeRequest geocodeRequest = new GeocodeService.GeocodeRequest(); 
      geocodeRequest.Credentials = new Credentials(); 
      geocodeRequest.Credentials.ApplicationId = ((ApplicationIdCredentialsProvider)BingMap.CredentialsProvider).ApplicationId; 
      geocodeRequest.Query = strAddress; 
      geocodeService.GeocodeAsync(geocodeRequest, waypointIndex); 
  } 
  
  
  private void geocodeService_GeocodeCompleted(object sender, GeocodeService.GeocodeCompletedEventArgs e) 
  { 
      GeocodeResult result = null; 
  
      if (e.Result.Results.Count > 0) 
      { 
       result = e.Result.Results[0]; 
       if (result != null) 
       { 
        // this.ShowMarker(result); 
        this.ShowShip(result); 
  
  
       } 
      } 
  
  } 
  

Answer 1

可以延長GeocodeService.GeocodeServiceClient添加這些屬性，然後在事件方法使用發送者參數geocodeService_GeocodeCompleted：

var service = (GeocodeService.GeocodeServiceClient) sender; 

的快速和骯髒（IMHO）版本是使用lambda表達式：

Pass parameter to EventHandler

Answer 2

它看起來像GeocodeCompletedEventArgs延伸AsyncCompletedEventArgs。 AsyncCompletedEventArgs的屬性爲UserState，可用於存儲異步事件的狀態信息。此狀態通常作爲參數傳遞給引發事件的方法。

更多信息請參見該問題：Bing GeocodeService userState usage as custom additional parameter