c# - 将参数传递给 WebClient.DownloadFileCompleted 事件

Question

我正在使用 WebClient.DownloadFileAsync() 方法，想知道如何将参数传递给 WebClient.DownloadFileCompleted 事件(或任何其他事件这很重要)，并在调用的方法中使用它。

我的代码:

public class MyClass
{
    string downloadPath = "some_path";
    void DownloadFile()
    {
        int fileNameID = 10;
        WebClient webClient = new WebClient();
        webClient.DownloadFileCompleted += DoSomethingOnFinish;
        Uri uri = new Uri(downloadPath + "\" + fileNameID );
        webClient.DownloadFileAsync(uri,ApplicationSettings.GetBaseFilesPath +"\" + fileNameID); 
    }

    void DoSomethingOnFinish(object sender, AsyncCompletedEventArgs e)
    {
        //How can i use fileNameID's value here?
    }

}

如何将参数传递给 DoSomethingOnFinish()？

Answer 1

您可以使用 webClient.QueryString.Add("FileName", YourFileNameID); 添加额外信息。

然后在您的 DoSomethingOnFinish 函数中访问它，

使用 string myFileNameID = ((System.Net.WebClient)(sender)).QueryString["FileName"]; 接收文件名。

代码应该是这样的:

string downloadPath = "some_path";
void DownloadFile()
{
    int fileNameID = 10;
    WebClient webClient = new WebClient();
    webClient.DownloadFileCompleted += new AsyncCompletedEventHandler(DoSomethingOnFinish);
    webClient.QueryString.Add("fileName", fileNameID.ToString());
    Uri uri = new Uri(downloadPath + "\\" + fileNameID);
    webClient.DownloadFileAsync(uri,ApplicationSettings.GetBaseFilesPath +"\\" + fileNameID); 
}

void DoSomethingOnFinish(object sender, AsyncCompletedEventArgs e)
{
    //How can i use fileNameID's value here?
    string myFileNameID = ((System.Net.WebClient)(sender)).QueryString["fileName"];
}

即使这可行，您也应该使用 Unity 的 UnityWebRequest 类。您可能没有听说过它，但它应该是这样的:

void DownloadFile(string url)
 {
     StartCoroutine(downloadFileCOR(url));
 }

 IEnumerator downloadFileCOR(string url)
 {
     UnityWebRequest www = UnityWebRequest.Get(url);

     yield return www.Send();
     if (www.isError)
     {
         Debug.Log(www.error);
     }
     else
     {
         Debug.Log("File Downloaded: " + www.downloadHandler.text);

         // Or retrieve results as binary data
         byte[] results = www.downloadHandler.data;
     }
 }