WPF程序拋出無法解釋的調用異常

Question

問題是：當我刪除第一個消息框行時，我的程序不運行並在if語句行中拋出「異常已被調用的目標拋出」。但是，當我離開郵箱時，它運行良好。有人可以向我解釋爲什麼會發生這種情況，我能做些什麼來解決它？順便說一句，我對WPF相當陌生，任何幫助將不勝感激。

public BrowserMode() { 

     InitializeComponent(); 

     MessageBox.Show("Entering Browser Mode"); 
     if (webBrowser1.Source.Scheme == "http") 
     { 
      //cancel navigation 
      //this.NavigationService.Navigating += new NavigatingCancelEventHandler(Cancel_Navigation); 

      qd = new QuestionData(); 

      // code where stuff happens 
      var url = webBrowser1.Source; 
      HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url); 

      // from h.RequestUri = "webcam://submit?question_id=45" 
      var parseUrl = request.RequestUri; //the uri that responded to the request. 
      MessageBox.Show("The requested URI is: " + parseUrl); 

Answer 1

這種工作不適合構造，應搬出後才WebBrowser滿載。你有兩種選擇：

1. 鉤Control.Loaded並在那裏執行此行爲。

   public BrowserMode() 
   { 
       InitializeComponent(); 
   
       this.Loaded += BroswerMode_Loaded; 
   } 
   
   void BrowserMode_Loaded(object sender, EventArgs e) 
   { 
       if (webBrowser1.Source != null 
       && webBrowser1.Source.Scheme == "http") 
       { 
        qd = new QuestionData(); 
        // ... 
       } 
   } 
   

2. 鉤WebBrowser.Navigating並在那裏執行此行爲。

   public BrowserMode() 
   { 
       InitializeComponent(); 
   
       this.webBrowser1.Navigating += WebBrowser_Navigating; 
   }  
   
   void WebBrowser_Navigating(object sender, NavigatingCancelEventArgs e) 
   { 
       if (e.Uri.Scheme == "http") 
       { 
        qd = new QuestionData(); 
        // ... 
       } 
   }