我最近在安装Blend 4后开始在我的App.xaml中收到错误，我的所有ViewModel现在都显示错误＃34;对象引用未设置为对象实例＆＃34;。我卸载了Blend 4，错误消失了几个小时，现在又回来了。
我已经检查了我在项目开始之前所做的每一次提交，问题仍然存在，我完全感到困惑。这里发生了什么？这导致我的窗口在设计模式中抛出关于无法找到资源的错误。
编辑：更新：我每隔几次构建它更改的应用程序，这次更改了UserControl上按钮的绑定后更改。之前是UserListViewModel和SettingViewModel。现在是它的SettingsViewModel和MainScreenViewModel。
App.xaml：
<Application x:Class="HelpScoutMetrics.App"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:vm="clr-namespace:HelpScoutMetrics.ViewModel">
<Application.Resources>
<ResourceDictionary>
<vm:MainScreenViewModel x:Key="MainScreenViewModel" />
<vm:SettingsViewModel x:Key="SettingsViewModel" />
<vm:UserListViewModel x:Key="UserListViewModel" />
<ResourceDictionary.MergedDictionaries>
<ResourceDictionary Source="pack://application:,,,/MahApps.Metro;component/Styles/Controls.xaml" />
<ResourceDictionary Source="pack://application:,,,/MahApps.Metro;component/Styles/Fonts.xaml" />
<ResourceDictionary Source="pack://application:,,,/MahApps.Metro;component/Styles/Colors.xaml" />
<ResourceDictionary Source="pack://application:,,,/MahApps.Metro;component/Styles/Accents/Blue.xaml" />
<ResourceDictionary Source="pack://application:,,,/MahApps.Metro;component/Styles/Accents/BaseLight.xaml" />
<ResourceDictionary Source="pack://application:,,,/MahApps.Metro;component/Styles/FlatButton.xaml" />
</ResourceDictionary.MergedDictionaries>
</ResourceDictionary>
</Application.Resources>
的ViewModels：
public class MainScreenViewModel : ViewModelBase
{
public MainScreenViewModel()
{
QuickStatistics = new QuickStats();
QuickStatistics.UserQuickStats = new ObservableCollection<UserQuickStat>();
QuickStatistics.UserQuickStats.Add(new UserQuickStat() { Name = "Test", TotalConversations = 93, TotalReplies = 57 });
ApplicationData.MainViewModel = this; // Temp for debug of issues
}
public static Logger logger = LogManager.GetLogger("MainScreenViewModel");
public MainWindow Window { get; set; }
private UserReport m_UserOverall;
public UserReport UserOverall
{
get { return m_UserOverall; }
set { m_UserOverall = value; RaisePropertyChanged("UserOverall"); }
}
private QuickStats m_QuickStatistics;
public QuickStats QuickStatistics
{
get { return m_QuickStatistics; }
set { m_QuickStatistics = value; RaisePropertyChanged("QuickStatistics"); }
}
private DateTime m_SelectedDate;
public DateTime SelectedDate
{
get { return m_SelectedDate; }
set { m_SelectedDate = value; RaisePropertyChanged("SelectedDate"); }
}
private ObservableCollection<DateTime> m_SelectedDates;
public ObservableCollection<DateTime> SelectedDates
{
get { return m_SelectedDates; }
set { m_SelectedDates = value; RaisePropertyChanged("SelectedDates"); }
}
private bool m_EnableLoadQuickStatsButton;
public bool EnableLoadQuickStatsButton
{
get { return m_EnableLoadQuickStatsButton; }
set { m_EnableLoadQuickStatsButton = value; RaisePropertyChanged("EnableLoadQuickStatsButton"); }
}
private bool m_EnableLoadQuickStatsButtonTest = false;
public bool EnableLoadQuickStatsButtonTest
{
get { return m_EnableLoadQuickStatsButtonTest; }
set { m_EnableLoadQuickStatsButtonTest = value; RaisePropertyChanged("EnableLoadQuickStatsButtonTest"); }
}
public void NewUser()
{
QuickStatistics.UserQuickStats.Add(new UserQuickStat() { Name = "Test2", TotalConversations = 953, TotalReplies = 577 });
}
public void OpenSettings()
{
if(Window.SettingsFlyout.IsOpen)
{
Window.SettingsFlyout.IsOpen = false;
logger.Log(LogLevel.Info, "Closed Settings Flyout");
}
else
{
SettingsViewModel viewModel = Window.SettingsFlyout.DataContext as SettingsViewModel;
viewModel.MainWindow = Window;
viewModel.LoadSettings();
Window.SettingsFlyout.IsOpen = true;
logger.Log(LogLevel.Info, "Opened Settings Flyout");
}
}
public void OpenUsersList()
{
if(Window.UserListFlyout.IsOpen)
{
Window.UserListFlyout.IsOpen = false;
logger.Log(LogLevel.Info, "Closed Users List Flyout");
}
else
{
UserListViewModel viewModel = Window.UserListFlyout.DataContext as UserListViewModel;
UserListView userListView = Window.UserListFlyoutView;
viewModel.UserListView = userListView;
viewModel.MainWindow = Window;
viewModel.SetupFreshViewModel();
Window.UserListFlyout.IsOpen = true;
logger.Log(LogLevel.Info, "Opened Users List Flyout");
}
}
public void OpenLogWindow()
{
int count = ApplicationData.MainLogEntries.LogEvents.Count;
NLogViewerView window = new NLogViewerView();
window.Show();
logger.Log(LogLevel.Info, "Opened Log Window");
EnableLoadQuickStatsButtonTest = true;
}
public void RefreshView()// Temp for debug of issues
{
foreach (string name in MiscMethods.GetPropertyNames(this))
{
RaisePropertyChanged(name);
}
}
}
public class SettingsViewModel : ViewModelBase
{
public SettingsViewModel()
{
SettingsWindowLogic.LoadSettings(this);
}
private static Logger logger = LogManager.GetLogger("SettingsViewModel");
public MainWindow MainWindow { get; set; }
private string m_APIKey;
public string APIKey
{
get { return m_APIKey; }
set
{
m_APIKey = value; TriedToValidateKey = false;
KeyValidationButtonText = "Verify Key";
VerifyButtonBackground = new SolidColorBrush(Color.FromArgb(255, 213, 213, 213));
ApplicationData.ApplicationSettings.ValidAPIKeyExists = false;
RaisePropertyChanged("APIKey");
}
}
private bool m_SaveAPIKey = true;
public bool SaveAPIKey
{
get { return m_SaveAPIKey; }
set { m_SaveAPIKey = value; RaisePropertyChanged("SaveAPIKey"); }
}
/*====================================================================
* Key Validation & Button
* ==================================================================*/
private bool m_ValidKey;
public bool ValidKey
{
get { return m_ValidKey; }
set
{
m_ValidKey = value;
if(value)
{
KeyValidationButtonText = "Valid!";
VerifyButtonBackground = new SolidColorBrush(Color.FromArgb(255, 18, 145, 47));
ApplicationData.ApplicationSettings.ValidAPIKeyExists = true;
}
else
{
KeyValidationButtonText = "Invalid";
VerifyButtonBackground = new SolidColorBrush(Color.FromArgb(255, 153, 18, 18));
ApplicationData.ApplicationSettings.ValidAPIKeyExists = false;
}
RaisePropertyChanged("ValidKey");
}
}
//Will be true when the eky is in process of verification
private bool m_CurrentlyVerifyingKey;
public bool CurrentlyVerifyingKey
{
get { return m_CurrentlyVerifyingKey; }
set
{
if (value)
{
KeyValidationButtonText = "Verifying...";
}
m_CurrentlyVerifyingKey = value;
RaisePropertyChanged("CurrentlyVerifyingKey");
}
}
private bool m_TriedToValidateKey;
public bool TriedToValidateKey
{
get { return m_TriedToValidateKey; }
set { m_TriedToValidateKey = value; RaisePropertyChanged("TriedToValidateKey"); }
}
private string m_KeyValidationButtonText = "Verify Key";
public string KeyValidationButtonText
{
get { return m_KeyValidationButtonText; }
set { m_KeyValidationButtonText = value; RaisePropertyChanged("KeyValidationButtonText"); }
}
private Brush m_VerifyButtonBackground = new SolidColorBrush(Color.FromArgb(255, 213, 213, 213));
public Brush VerifyButtonBackground
{
get { return m_VerifyButtonBackground; }
set { m_VerifyButtonBackground = value; RaisePropertyChanged("VerifyButtonBackground"); }
}
public async void VerifyAPIKey()
{
//Task<Paged<Mailbox>> testPull = new Task<Paged<Mailbox>>(() => client.ListMailboxes());
Task<bool> results = new Task<bool>(() => SettingsWindowLogic.VerifyAPIKey(APIKey));
CurrentlyVerifyingKey = true;
results.Start();
CurrentlyVerifyingKey = false;
if (await results)
{
ValidKey = true;
}
else
{
ValidKey = false;
}
TriedToValidateKey = true;
}
public void SaveSettings()
{
SettingsWindowLogic.SaveSettings(this);
logger.Log(LogLevel.Debug, "Saved Settings");
CloseFlyout();
}
public void LoadSettings()
{
SettingsWindowLogic.LoadSettings(this);
}
public void ResetSettings()
{
APIKey = string.Empty;
SaveAPIKey = false;
ApplicationData.ApplicationSettings.ValidAPIKeyExists = false;
logger.Log(LogLevel.Debug, "Reset Settings");
}
public void CloseFlyout()
{
MainWindow.SettingsFlyout.IsOpen = false;
logger.Log(LogLevel.Info, "Closed Settings Flyout");
}
}
public class UserListViewModel : ViewModelBase
{
public UserListViewModel()
{
// LoadUserList();
}
public static Logger logger = LogManager.GetLogger("UserListViewModel");
public MainWindow MainWindow { get; set; }
public UserListView UserListView { get; set; }
private UserList m_UserList;
public UserList UsersList
{
get { return m_UserList; }
set { m_UserList = value; RaisePropertyChanged("UsersList"); }
}
private List<string> m_TestItems;
public List<string> TestItems
{
get { return m_TestItems; }
set { m_TestItems = value; RaisePropertyChanged("TestItems"); }
}
private string m_NewUserName;
public string NewUserName
{
get { return m_NewUserName; }
set { m_NewUserName = value; RaisePropertyChanged("NewUserName"); }
}
private string m_HelpScoutUserListStatus = "Attempting To Load HelpScout Users...";
public string HelpScoutUserListStatus
{
get { return m_HelpScoutUserListStatus; }
set { m_HelpScoutUserListStatus = value; RaisePropertyChanged("HelpScoutUserListStatus"); }
}
private Brush m_HelpScoutUserListStatusColor = new SolidColorBrush(Color.FromArgb(255, 187, 95, 32));
public Brush HelpScoutUserListStatusColor
{
get { return m_HelpScoutUserListStatusColor; }
set { m_HelpScoutUserListStatusColor = value; RaisePropertyChanged("HelpScoutUserListStatusColor"); }
}
private bool m_HelpScoutUserListLoaded;
public bool HelpScoutUserListLoaded
{
get { return m_HelpScoutUserListLoaded; }
set
{
if(value)
{
HelpScoutUserListStatus = UserListWindowLogic.HelpScutUseListStringStatus[0];
HelpScoutUserListStatusColor = UserListWindowLogic.HelpScoutUserListStatusColors[0];
ReverifyUserList();
}
else
{
HelpScoutUserListStatus = UserListWindowLogic.HelpScutUseListStringStatus[1];
HelpScoutUserListStatusColor = UserListWindowLogic.HelpScoutUserListStatusColors[1];
}
m_HelpScoutUserListLoaded = value;
RaisePropertyChanged("HelpScoutUserListLoaded");
}
}
private List<User> m_HelpScoutUsersList;
public List<User> HelpScoutUsersList
{
get { return m_HelpScoutUsersList; }
set { m_HelpScoutUsersList = value; RaisePropertyChanged("HelpScoutUsersList"); }
}
private List<string> m_HelpScoutUsersListStrings = new List<string>();
public List<string> HelpScoutUsersListStrings
{
get { return m_HelpScoutUsersListStrings; }
set { m_HelpScoutUsersListStrings = value; RaisePropertyChanged("HelpScoutUsersListStrings"); }
}
public async void RetrieveHelpScoutUserList()
{
Task<List<User>> task = new Task<List<User>>(() => UserListWindowLogic.RetrieveHelpScoutUserList());
task.Start();
List<User> usersList = await task;
if(usersList != null)
{
HelpScoutUsersList = usersList;
foreach(User userObject in usersList)
{
HelpScoutUsersListStrings.Add(userObject.Name);
}
HelpScoutUserListLoaded = true;
}
else
{
HelpScoutUserListLoaded = false;
}
}
private User MatchUserID(string name)
{
return UserListWindowLogic.FindUserByName(name, HelpScoutUsersList);
}
public void RemoveUser()
{
User user = UserListView.NamesDataGrid.SelectedItem as User;
UsersList.Users.Remove(user);
logger.Log(LogLevel.Debug, "Removed User: " + user.Name);
}
public void AddUser()
{
if (!string.IsNullOrEmpty(NewUserName) && HelpScoutUserListLoaded)
{
User user = MatchUserID(NewUserName);
if(user != null)
{
UsersList.Users.Add(user);
logger.Log(LogLevel.Debug, "Added New Valid User: " + user.Name);
}
else
{
UsersList.Users.Add(new User() { Name = NewUserName });
logger.Log(LogLevel.Debug, "Added New User: " + NewUserName);
}
}
else
{
UsersList.Users.Add(new User() { Name = NewUserName });
logger.Log(LogLevel.Debug, "Added New User: " + NewUserName);
}
ClearNewUserNameTextBox();
}
//Clears the new user textbox
public void ClearNewUserNameTextBox()
{
NewUserName = string.Empty;
}
public void SetupFreshViewModel()
{
m_HelpScoutUserListLoaded = false;
HelpScoutUserListStatusColor = new SolidColorBrush(Color.FromArgb(255, 187, 95, 32));
HelpScoutUserListStatus = "Attempting To Load HelpScout Users...";
LoadUserList();
RetrieveHelpScoutUserList();
}
public void SaveUserList()
{
UserListWindowLogic.SaveUserList(this);
logger.Log(LogLevel.Debug, "Saved Users List");
CloseFlyout();
}
public void ReverifyUserList()
{
UserListWindowLogic.CheckUserListValidity(HelpScoutUsersList);
LoadUserList();
}
public void LoadUserList()
{
UserList userList;
if(ApplicationData.Users != null)
{
userList = XMLSerialize<UserList>.CopyData(ApplicationData.Users);
}
else
{
userList = UserListWindowLogic.CreateNewUserList();
}
UsersList = userList;
}
public void ResetUserList()
{
UsersList = new UserList();
logger.Log(LogLevel.Debug, "Reset Users List");
}
public void CloseFlyout()
{
MainWindow.UserListFlyout.IsOpen = false;
logger.Log(LogLevel.Info, "Closed Users List Flyout");
}
}
public class ViewModelBase : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
public void RaisePropertyChanged(String propertyName)
{
PropertyChangedEventHandler temp = PropertyChanged;
if (temp != null)
{
temp(this, new PropertyChangedEventArgs(propertyName));
}
}
public bool IsInDesignMode
{
get
{
var prop = DesignerProperties.IsInDesignModeProperty;
return (bool)DependencyPropertyDescriptor
.FromProperty(prop, typeof(FrameworkElement))
.Metadata.DefaultValue;
}
}
}
答案 0 :(得分：2)
您需要确保视图模型的构造函数可以在设计时初始化，如果您在构造函数中使用了一些无法在设计时初始化的依赖项，则需要将其放在条件块中： if(!IsInDesignMode)