我有一个带有SQL数据库/实体框架的ASP.NET Web API，我将用它作为我正在构建的应用程序的服务器端。客户端现在将是WPF。我在确定MVVM控件从服务器访问数据的最佳方法时遇到了一些麻烦。我为MVVM完成的所有教程和课程都直接连接到本地数据库，并在加载控件时更新。我想要的是一个常量循环，其中API每分钟调用一次，控件中的数据在该点自动刷新。我有两个主要控件工作（遇到一个问题从另一个线程更新集合，并不得不使用App.Current.Dispatcher.Invoke），但我不确定我是否保持最佳实践运行API调用直接来自视图模型。此外，我需要能够在视图模型之间共享数据。
ScheduledForwardsViewModel具有ActiveForwardsViewModel所需的数据，ActiveForwardsViewModel具有CreateForwardsViewModel所需的数据。每个条目的ActiveForward需要能够查看每个相应的计划项目的计划日期，以便它可以找到下一个事件并显示在ActiveForwardsView中发生该事件之前的剩余时间。 CreateForwardView只需要访问在ActiveForwards数据操作期间创建的AllUsers，AllGroups，AllContacts可观察集合，以便在计划新的转发时可以在下拉字段中使用该数据。我还没有能够让下拉列表工作。我确实可以使用静态对象访问ScheduledForwardsView所需的信息，但我觉得可能有更好的方法。当我的应用程序的一部分已经拥有我需要的数据时，我宁愿不要为相同的数据多次调用API。
基本布局：
MainWindow
CreateForwardView (with view model)
[Drop down boxes to select user and schedule forward]
[Buttons, etc.]
[TabControl]
[TabItem: Active Forwards]
ActiveForwardsView (with view model)
[TabItem: Scheduled Forwards]
ScheduledForwardsView (with view model)
[EndTabControl]
ActiveForwardsViewModel如下所示。 ScheduledForwardsViewModel本质上是相同的，但它调用一个不同的API方法并包含我在ActiveForwardsViewModel中使用的静态对象（请参阅我继续使用UpdateUserObjects之前等待ScheduledForwardsViewModel完成1次运行的部分）。这似乎不是正确的做法，但我这样设置就是为了让我可以转向其他事情。
public class ActiveForwardsViewModel : INotifyPropertyChanged
{
private CancellationToken updater = default(CancellationToken);
private AppLog log;
private FFObject _selectedObject;
private ObservableCollection<FFObject> _activeForwards;
public ObservableCollection<FFObject> ActiveForwards
{
get { return _activeForwards; }
set
{
if (_activeForwards != value)
{
_activeForwards = value;
PropertyChanged(this, new PropertyChangedEventArgs("ActiveForwards"));
}
}
}
public ObservableCollection<FFObject> AllUsers { get; set; }
public ObservableCollection<FFObject> AllGroups { get; set; }
public ObservableCollection<FFObject> AllContacts { get; set; }
public ObservableCollection<FFObject> AllObjects { get; set; }
public bool Running = false;
public bool FirstRunComplete = false;
public event PropertyChangedEventHandler PropertyChanged = delegate { };
public ActiveForwardsViewModel()
{
if (DesignerProperties.GetIsInDesignMode(new System.Windows.DependencyObject()))
{
updater.ThrowIfCancellationRequested();
return;
}
ActiveForwards = new ObservableCollection<FFObject>();
AllUsers = new ObservableCollection<FFObject>();
AllGroups = new ObservableCollection<FFObject>();
AllContacts = new ObservableCollection<FFObject>();
AllObjects = new ObservableCollection<FFObject>();
StartUpdater(updater);
RemoveForwardCommand = new RelayCommand(OnRemove, CanRemove);
}
public async Task StartUpdater(CancellationToken token = default(CancellationToken))
{
while (!token.IsCancellationRequested)
{
Running = true;
await this.Update();
FirstRunComplete = true;
try
{
await Task.Delay(TimeSpan.FromMinutes(1), token);
}
catch (TaskCanceledException)
{
Running = false;
break;
}
}
}
private List<FFObject> UpdateAllObjectList(string strJson)
{
var serializer = new JavaScriptSerializer();
return serializer.Deserialize<List<FFObject>>(strJson);
//return AllObjects;
}
public string GetString(string method)
{
using (var client = new WebClient())
{
var url = string.Format("https://mywebapi.domain.com/api/{0}", method);
return client.DownloadString(url);
}
}
public async Task Update()
{
Func<string, List<FFObject>> getUsersJson = UpdateAllObjectList;
await Task<string>.Factory.StartNew(() => GetString("Users"))
.ContinueWith(antecendent => getUsersJson(antecendent.Result))
.ContinueWith(antecendent => UpdateUserObjects(antecendent.Result));
}
private void CheckRemoved(List<FFObject> all)
{
List<FFObject> RemoveObjects = new List<FFObject>();
foreach (var obj in ActiveForwards)
{
var newObj = all.FirstOrDefault(i => i.ID == obj.ID);
if (newObj == null)
{
RemoveObjects.Add(obj);
}
else
{
if (!(bool) newObj.IsForwarded)
{
RemoveObjects.Add(obj);
}
}
}
foreach (var obj in RemoveObjects)
{
App.Current.Dispatcher.Invoke((Action)delegate
{
ActiveForwards.Remove(obj);
});
}
}
private void UpdateUserObjects(List<FFObject> all)
{
Debug.WriteLine("Starting UpdateUserObject");
if (all != null)
{
AllObjects = new ObservableCollection<FFObject>(all);
CheckRemoved(all);
var x = 0;
while (!ScheduledForwardsViewModel.RunOnce && x < 5)
{
System.Threading.Thread.Sleep(1000);
x++;
}
foreach (var obj in all)
{
if (obj.ObjectType.ToLower() == "user")
{
var existing = AllUsers.FirstOrDefault(i => i.DistinguishedName == obj.DistinguishedName);
if (existing != null)
{
existing.ForwardedTo = obj.ForwardedTo;
existing.ForwardedToAd = obj.ForwardedToAd;
existing.ForwardedToDn = obj.ForwardedToDn;
existing.ForwardedToPk = obj.ForwardedToPk;
existing.ForwardedToDisplay = obj.ForwardedToDisplay;
existing.IsForwarded = obj.IsForwarded;
existing.DeliverAndRedirect = obj.DeliverAndRedirect;
existing.IsScheduled = obj.IsScheduled;
existing.TimeLeft = obj.TimeLeft;
}
else
{
//AllUsers.Add(obj);
App.Current.Dispatcher.Invoke((Action)delegate // <--- HERE
{
AllUsers.Add(obj);
});
}
if (obj.IsForwarded ?? false)
{
existing = ActiveForwards.FirstOrDefault(i => i.DistinguishedName == obj.DistinguishedName);
obj.TimeLeft = "";
var now = DateTime.Now;
var TimeRemaining = new TimeSpan?();
foreach (var schedule in ScheduledForwardsViewModel.ScheduledForwards)
{
if (schedule.DistinguishedName == obj.DistinguishedName)
{
if (schedule.StopJobStatus == "Scheduled")
{
if (TimeRemaining == null)
{
TimeRemaining = schedule.StopTime - now;
}
else
{
if (schedule.StopTime - now < TimeRemaining)
{
TimeRemaining = schedule.StopTime - now;
}
}
}
}
}
if (TimeRemaining != null)
{
var remaining = (TimeSpan)TimeRemaining;
var min = new int();
if (remaining.Seconds > 30)
{
min = remaining.Minutes + 1;
}
double m = remaining.Minutes / (double)60;
double hm = remaining.Hours + m;
double h = hm / 24;
double dh = remaining.Days + h;
if (remaining.Days > 0)
{
var daysleft = Math.Round(dh, 2);
var quarterRound = Math.Round(dh * 4, MidpointRounding.ToEven) / 4;
obj.TimeLeft = quarterRound + "d";
}
else if (remaining.Hours > 0)
{
var hoursleft = Math.Round(hm, 2);
var quarterRound = Math.Round(hm * 4, MidpointRounding.ToEven) / 4;
obj.TimeLeft = quarterRound + "h";
obj.TimeLeft = remaining.Hours + "h" + remaining.Minutes + "m";
}
else
{
if (min == 0)
{
obj.TimeLeft = "< 30s";
}
else
{
obj.TimeLeft = min + "m";
}
}
}
if (existing != null)
{
existing.ForwardedTo = obj.ForwardedTo;
existing.ForwardedToAd = obj.ForwardedToAd;
existing.ForwardedToDn = obj.ForwardedToDn;
existing.ForwardedToPk = obj.ForwardedToPk;
existing.ForwardedToDisplay = obj.ForwardedToDisplay;
existing.IsForwarded = obj.IsForwarded;
existing.DeliverAndRedirect = obj.DeliverAndRedirect;
existing.IsScheduled = obj.IsScheduled;
existing.TimeLeft = obj.TimeLeft;
}
else
{
//ActiveForwards.Add(obj);
App.Current.Dispatcher.Invoke((Action)delegate // <--- HERE
{
ActiveForwards.Add(obj);
});
}
}
}
else if (obj.ObjectType.ToLower() == "group")
{
if (obj.IsForwarded ?? false)
{
var existing = AllGroups.FirstOrDefault(i => i.DistinguishedName == obj.DistinguishedName);
if (existing != null)
{
existing.ForwardedTo = obj.ForwardedTo;
existing.ForwardedToAd = obj.ForwardedToAd;
existing.ForwardedToDn = obj.ForwardedToDn;
existing.ForwardedToPk = obj.ForwardedToPk;
existing.ForwardedToDisplay = obj.ForwardedToDisplay;
existing.IsForwarded = obj.IsForwarded;
existing.DeliverAndRedirect = obj.DeliverAndRedirect;
existing.IsScheduled = obj.IsScheduled;
existing.TimeLeft = obj.TimeLeft;
}
else
{
//AllGroups.Add(obj);
App.Current.Dispatcher.Invoke((Action)delegate // <--- HERE
{
AllGroups.Add(obj);
});
}
}
}
else if (obj.ObjectType.ToLower() == "contact")
{
if (obj.IsForwarded ?? false)
{
var existing = AllContacts.FirstOrDefault(i => i.DistinguishedName == obj.DistinguishedName);
if (existing != null)
{
existing.ForwardedTo = obj.ForwardedTo;
existing.ForwardedToAd = obj.ForwardedToAd;
existing.ForwardedToDn = obj.ForwardedToDn;
existing.ForwardedToPk = obj.ForwardedToPk;
existing.ForwardedToDisplay = obj.ForwardedToDisplay;
existing.IsForwarded = obj.IsForwarded;
existing.DeliverAndRedirect = obj.DeliverAndRedirect;
existing.IsScheduled = obj.IsScheduled;
existing.TimeLeft = obj.TimeLeft;
}
else
{
//AllContacts.Add(obj);
App.Current.Dispatcher.Invoke((Action)delegate // <--- HERE
{
AllContacts.Add(obj);
});
}
}
}
else
{
throw new NotImplementedException();
}
}
}
RunOnce = true;
}