我一直在处理能够从picasa获取相册的Windows Phone应用程序，但是我收到了一个错误：'System.Reflection.TargetInvocationException'中出现System.ni.dll类型的例外但未处理相册page.xaml.cs
using System;
using System.Collections.Generic;
using System.Net;
using System.Windows;
using System.Windows.Controls;
using Microsoft.Phone.Controls;
using System.Collections;
using System.IO.IsolatedStorage;
namespace MyPicasa
{
public partial class AlbumsPage : PhoneApplicationPage
{
private IsolatedStorageSettings appSettings;
private const string emailKey = "emailKey";
private const string passwordKey = "passwordKey";
private const string usernameKey = "usernameKey";
private string username = "";
private string email = "";
private string password = "";
private string dataFeed = "";
private App app = App.Current as App;
// Handle loading animation in this page
public bool ShowProgress
{
get { return (bool)GetValue(ShowProgressProperty); }
set { SetValue(ShowProgressProperty, value); }
}
public static readonly DependencyProperty ShowProgressProperty =
DependencyProperty.Register("ShowProgress", typeof(bool), typeof(AlbumsPage), new PropertyMetadata(false));
// Constructor
public AlbumsPage()
{
InitializeComponent();
appSettings = IsolatedStorageSettings.ApplicationSettings;
}
// Navigate to this page
protected override void OnNavigatedTo(System.Windows.Navigation.NavigationEventArgs e)
{
base.OnNavigatedTo(e);
// load and show saved username from isolated storage
if (appSettings.Contains(usernameKey))
{
string differentUsername = (string)appSettings[usernameKey];
if (differentUsername != "") username = differentUsername;
}
// load and show saved email from isolated storage
if (appSettings.Contains(emailKey))
{
email = (string)appSettings[emailKey]; // for example firstname.lastname@gmail.com
if (username == "" && email.IndexOf("@") != -1) username = email.Substring(0, email.IndexOf("@")); // firstname.lastname
dataFeed = String.Format("http://picasaweb.google.com/data/feed/api/user/{0}?alt=json", username);
}
// load password from isolated storage
if (appSettings.Contains(passwordKey))
{
password = (string)appSettings[passwordKey];
}
// we are coming back from AlbumPage
if (e.NavigationMode == System.Windows.Navigation.NavigationMode.Back)
{
AlbumsListBox.ItemsSource = app.albums;
AlbumsListBox.SelectedIndex = -1;
}
else
{
// get authentication from Google
GetAuth();
}
}
// get authentication from Google
private void GetAuth()
{
ShowProgress = true;
string service = "lh2"; // Picasa
string accountType = "GOOGLE";
WebClient webClient = new WebClient();
Uri uri = new Uri(string.Format("https://www.google.com/accounts/ClientLogin?Email={0}&Passwd={1}&service={2}&accountType={3}", email, password, service, accountType));
webClient.DownloadStringCompleted += new DownloadStringCompletedEventHandler(AuthDownloaded);
webClient.DownloadStringAsync(uri);
}
// handle authentication from google
private void AuthDownloaded(object sender, DownloadStringCompletedEventArgs e)
{
try
{
if (e.Result != null && e.Error == null)
{
app.auth = "";
int index = e.Result.IndexOf("Auth=");
if (index != -1)
{
app.auth = e.Result.Substring(index + 5);
}
if (app.auth != "")
{
// get albums from Google
GetAlbums();
return;
}
}
MessageBox.Show("Cannot get authentication from google. Check your login and password.");
ShowProgress = false;
}
catch (WebException)
{
MessageBox.Show("Cannot get authentication from google. Check your login and password.");
ShowProgress = false;
}
}
// Get albums from Google
private void GetAlbums()
{
WebClient webClient = new WebClient();
webClient.Headers[HttpRequestHeader.Authorization] = "GoogleLogin auth=" + app.auth;
Uri uri = new Uri(dataFeed, UriKind.Absolute);
webClient.DownloadStringCompleted += new DownloadStringCompletedEventHandler(AlbumsDownloaded);
webClient.DownloadStringAsync(uri);
}
// Albums loaded from Google
public void AlbumsDownloaded(object sender, DownloadStringCompletedEventArgs e)
{
try
{
if (e.Result == null || e.Error != null)
{
MessageBox.Show("Cannot get albums data from Picasa server!");
ShowProgress = false;
return;
}
else
{
// Deserialize JSON string to dynamic object
IDictionary<string, object> json = (IDictionary<string, object>)SimpleJson.DeserializeObject(e.Result);
// Feed object
IDictionary<string, object> feed = (IDictionary<string, object>)json["feed"];
// Author List
IList author = (IList)feed["author"];
// First author (and only)
IDictionary<string, object> firstAuthor = (IDictionary<string, object>)author[0];
// Album entries
IList entries = (IList)feed["entry"];
// Delete previous albums from albums list
app.albums.Clear();
// Find album details
for (int i = 0; i < entries.Count; i++)
{
// Create a new Album
Album album = new Album();
// Album entry object
IDictionary<string, object> entry = (IDictionary<string, object>)entries[i];
// Published object
IDictionary<string, object> published = (IDictionary<string, object>)entry["published"];
// Get published date
album.published = (string)published["$t"];
// Title object
IDictionary<string, object> title = (IDictionary<string, object>)entry["title"];
// Album title
album.title = (string)title["$t"];
// Link List
IList link = (IList)entry["link"];
// First link is album data link object
IDictionary<string, object> href = (IDictionary<string, object>)link[0];
// Get album data addres
album.href = (string)href["href"];
// Media group object
IDictionary<string, object> mediagroup = (IDictionary<string, object>)entry["media$group"];
// Media thumbnail object list
IList mediathumbnailList = (IList)mediagroup["media$thumbnail"];
// First thumbnail object (smallest)
var mediathumbnail = (IDictionary<string, object>)mediathumbnailList[0];
// Get thumbnail url
album.thumbnail = (string)mediathumbnail["url"];
// Add album to albums
app.albums.Add(album);
}
// Hide loading... animation
ShowProgress = false;
// Add albums to AlbumListBox
AlbumsListBox.ItemsSource = app.albums;
}
}
catch (WebException)
{
MessageBox.Show("Cannot get albums data from Picasa server!");
ShowProgress = false;
}
catch (KeyNotFoundException)
{
MessageBox.Show("Cannot load images from Picasa Server - JSON parsing error happened!");
ShowProgress = false;
}
}
// Handle selection from AlbumListBox
private void AlbumsListBox_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
// If real selection is happened, go to a AlbumPage
if (AlbumsListBox.SelectedIndex == -1) return;
app.selectedAlbumIndex = AlbumsListBox.SelectedIndex;
this.NavigationService.Navigate(new Uri("/AlbumPage.xaml?SelectedIndex=" + AlbumsListBox.SelectedIndex, UriKind.Relative));
}
}
}
错误发生在这行代码中：
if (e.Result != null && e.Error == null)
错误详情：
{System.Reflection.TargetInvocationException: An exception occurred during the operation, making the result invalid. Check InnerException for exception details. ---> System.Net.WebException: The remote server returned an error: NotFound. ---> System.Net.WebException: The remote server returned an error: NotFound.
at System.Net.Browser.ClientHttpWebRequest.InternalEndGetResponse(IAsyncResult asyncResult)
at System.Net.Browser.ClientHttpWebRequest.<>c__DisplayClasse.<EndGetResponse>b__d(Object sendState)
at System.Net.Browser.AsyncHelper.<>c__DisplayClass1.<BeginOnUI>b__0(Object sendState)
--- End of inner exception stack trace ---
at System.Net.Browser.AsyncHelper.BeginOnUI(SendOrPostCallback beginMethod, Object state)
at System.Net.Browser.ClientHttpWebRequest.EndGetResponse(IAsyncResult asyncResult)
at System.Net.WebClient.GetWebResponse(WebRequest request, IAsyncResult result)
at System.Net.WebClient.DownloadBitsResponseCallback(IAsyncResult result)
--- End of inner exception stack trace ---
at System.ComponentModel.AsyncCompletedEventArgs.RaiseExceptionIfNecessary()
at System.Net.DownloadStringCompletedEventArgs.get_Result()
at MyPicasa.AlbumsPage.AuthDownloaded(Object sender, DownloadStringCompletedEventArgs e)
at System.Net.WebClient.OnDownloadStringCompleted(DownloadStringCompletedEventArgs e)
at System.Net.WebClient.DownloadStringOperationCompleted(Object arg)}
答案 0 :(得分：0)
如果您收到System.Reflection.TargetInvocationException类型的无法处理的异常，理想情况下这意味着您正在调用未等待的async方法：