如何將參數傳遞給EventHandler

Question

不，它不是那種基本問題。我正在做一個應用程序，並得到一個類似的文件，文件將被下載，然後它將被上傳到FTP服務器，然後本地副本將被刪除，然後一個條目將被放置在該文件名的字典中。所以，代碼是

public void download_This_WebPage(string url, string cookies_String, string local_Saving_File_Name_With_Path) 
{ 
    WebClient wb = new WebClient(); 
    wb.Headers.Add(HttpRequestHeader.Cookie, cookies_String); 
    // Below I want to pass this local_File _Path to the event handler 
    wb.DownloadFileCompleted += new System.ComponentModel.AsyncCompletedEventHandler(wb,); 
    wb.DownloadFileAsync(new Uri(url), local_Saving_File_Name_With_Path + ".html"); 
} 

public void data_Download_Completed(Object sender, System.ComponentModel.AsyncCompletedEventArgs args) 
{ 
     //use the file name to upload the file to FTP 

} 

public FTP_Completed 
{ 
    // Delete the file 
} 

但是，我不知道如何將該文件名傳遞給download_Completed事件處理程序。可以有人指導我在這

編輯： 謝謝你從「達林」和「弗雷德裏克」的答案。是否有自定義的數據傳遞給（已定義）事件處理類似下面

void main_Fn() 
{ 
    string my_Data = "Data"; 
    some_object a = new some_object(); 
    some_Object.click_event += new eventHandler(click_Happened); 
    (Assume that the event passes two ints, I also want to pass the string "my_Data" 
     to "click_Happened") 
    some_object.start(); 
} 

void click_Happened(int a, int b) 
{ 
    // I want to get the string "my_Data" here. 
} 

總之如何欺騙簽名任何通用的方式？

Answer 1

可以傳遞userToken參數中的文件名稱爲DownloadFileAsync()。當操作完成後，它會在AsyncCompletedEventArgs參數傳遞的UserState財產可供data_Download_Completed()：

string filename = local_Saving_File_Name_With_Path + ".html"; 
wb.DownloadFileAsync(new Uri(url), filename, filename); 

然後：

public void data_Download_Completed(Object sender, 
    System.ComponentModel.AsyncCompletedEventArgs args) 
{ 
    string filename = (string) args.UserState; 
    // Now do something with 'filename'... 
} 

Answer 2

你可以使用DownloadFileAsync方法，可以讓你的UserState傳遞到完成處理的3擋的說法：

// subscribe to the completed event 
wb.DownloadFileCompleted += data_Download_Completed; 
string file = local_Saving_File_Name_With_Path + ".html"; 
wb.DownloadFileAsync(new Uri("url"), file, file); 

和處理程序中：

public void data_Download_Completed(Object sender, AsyncCompletedEventArgs args) 
{ 
    // extract the filename from the UserState of the args 
    string file = args.UserState as string; 
    ... 

}