[英]Nested Asynchronous function in Silverlight
I am trying to call a nested Asynchronous function but I am not getting the required data. 我试图调用嵌套的异步函数,但我没有得到所需的数据。 Since I am using a wcf service with Silverlight I can only use Asynchronous functions.
由于我在Silverlight中使用wcf服务,因此我只能使用异步函数。
In my code I am saving a set of rows containing userdata. 在我的代码中,我保存了一组包含userdata的行。 Before I save it I need to check the username is unique.
在我保存之前,我需要检查用户名是否唯一。 Now I only need to find out the first one and then break out of loop and show a message to the user.for simplicity sake, I have stripped the function of all the extra data and this is how it looks
现在我只需要找出第一个然后突破循环并向用户显示一条消息。为简单起见,我已经删除了所有额外数据的功能,这就是它的外观
private void SaveUsers(bool CloseForm)
{
ObservableCollection<User> _UpdatedUsers = new ObservableCollection<User>();
DatabaseServiceLocal _dataService = new DatabaseServiceLocal(Database);
foreach (UserViewModel _User in _AllUsers)
{
//bool success = _dataService.IsUserNameUnique(_User.UserName, _User.UserID, Database.CurrentClient.ClientID);
if (_User.Dirty && !_User.IsBlank)
{
_dataService.CheckIsUserNameUnique += (s, e) =>
{
if (e.IsUnique)
_UpdatedUsers.Add(_User.SaveAsUser());
else
{
_UpdatedUsers = new ObservableCollection<User>();
csaMessageBox.Show(string.Format("Username {0} is not allowed as it already exists in the system. Please choose a different username.", ""), null);
return;
}
};
_dataService.IsUserNameUnique(_User.UserName, _User.UserID, Database.CurrentClient.ClientID);
}
_dataService.UpdateStaffAndUsersCompleted += (s, e) =>
{
BusyIndicator = false;
if (e.Success)
{
}
if (CloseForm)
ReturnToHomePage();
else
{
LoadUsers();
OnUsersSaved();
}
}
BusyIndicator = true;
BusyMessage = "Saving...";
_dataService.UpdateUsers(Database.CurrentProject.ProjectID, Database.CurrentClient.ClientID, _UpdatedUsers, _DeletedProjectUsers);
}
In this case I am trying to find if the username is unique,show user a message and return. 在这种情况下,我试图找到用户名是否唯一,向用户显示一条消息并返回。 Obviously it's not as simple as that.I have tried a couple more different ways but it didn't work.
显然它不是那么简单。我尝试了几种不同的方式,但它没有用。 How do I get this working?
我该如何工作?
I think you can make your life easier by adding a couple of helper functions. 我认为通过添加几个辅助函数可以让您的生活更轻松。 The first one is an asynchronous function that checks whether a user is unique.
第一个是异步函数,用于检查用户是否唯一。 You may need to add some code to set
tcs.SetException
if there is an error. 如果出现错误,您可能需要添加一些代码来设置
tcs.SetException
。
private Task<bool> IsUserUniqueAsync(UserViewModel user, DatabaseServiceLocal dataService)
{
var tcs = new TaskCompletionSource<bool>();
dataService.CheckIsUserNameUnique += (s, e) =>
{
tcs.SetResult(e.IsUnique);
};
dataService.IsUserNameUnique(user.UserName, user.UserID, Database.CurrentClient.ClientID);
return tcs.Task;
}
The second one updates all the users asynchrnously 第二个异步更新所有用户
public Task<bool> UpdateUsersAsync(ObservableCollection<User> updatedUsers, DatabaseServiceLocal dataService)
{
var tcs = new TaskCompletionSource<bool>();
BusyIndicator = true;
BusyMessage = "Saving...";
dataService.UpdateStaffAndUsersCompleted += (s, e) =>
{
BusyIndicator = false;
tcs.SetResult(e.Success);
};
dataService.UpdateUsers(Database.CurrentProject.ProjectID, Database.CurrentClient.ClientID, updatedUsers, _DeletedProjectUsers);
return tcs.Task;
}
Then your SaveUsers
method becomes a bit simpler. 然后你的
SaveUsers
方法变得有点简单。
private async void SaveUsers(bool CloseForm)
{
ObservableCollection<User> _UpdatedUsers = new ObservableCollection<User>();
DatabaseServiceLocal _dataService = new DatabaseServiceLocal(Database);
Dictionary<Task<bool>, User> tasks = new Dictionary<Task<bool>, User>();
// start all tasks in parallel
foreach (UserViewModel _User in _AllUsers)
{
if (_User.Dirty && !_User.IsBlank)
{
tasks.Add(IsUserUniqueAsync(_User, _dataService), _User);
}
}
// process each task as it completes
while(tasks.Count() > 0 )
{
var task = await Task.WhenAny(tasks.Keys.ToArray());
if(task.Result)
{
_UpdatedUsers.Add(_User.SaveAsUser());
}
else
{
MessageBox.Show(string.Format("Username {0} is not allowed as it already exists in the system. Please choose a different username.", ""), null);
return;
}
tasks.Remove(task);
}
if( await UpdateUsersAsync(_UpdatedUsers, _dataService))
{
if (CloseForm)
ReturnToHomePage();
else
{
LoadUsers();
OnUsersSaved();
}
}
}
Your code would more or less look like this. 您的代码或多或少会像这样。
ObservableCollection<User> _UpdatedUsers = new ObservableCollection<User>();
int _verifiedUsersCount = 0;
DatabaseServiceLocal _dataService = new DatabaseServiceLocal(Database);
//Verify unique users
private void SaveUsers(bool CloseForm)
{
_dataService.CheckIsUserNameUnique += CheckIsUserNameUnique;
foreach (UserViewModel _User in _AllUsers)
{
//bool success = _dataService.IsUserNameUnique(_User.UserName, _User.UserID, Database.CurrentClient.ClientID);
if (_User.Dirty && !_User.IsBlank)
{
_dataService.IsUserNameUnique(_User.UserName, _User.UserID, Database.CurrentClient.ClientID);
}
}
}
//Store verified users to save
private void CheckIsUserNameUnique(object s, CheckIsUserNameUniqueEventArgs e)
{
if (e.IsUnique)
_UpdatedUsers.Add(_User.SaveAsUser());
else
{
csaMessageBox.Show(string.Format("Username {0} is not allowed as it already exists in the system. Please choose a different username.", ""), null);
}
verifiedUsersCount++;
//Call after all the users have been verified for uniqueness
if (_AllUsers.Count() == verifiedUsersCount)
{
OnUniqueUserVerifyComplete();
}
}
//Save verified users
private void OnUniqueUserVerifyComplete()
{
//No unique users
if (_UpdatedUsers.Count < 1) { return; }
_dataService.UpdateStaffAndUsersCompleted += (s, e) =>
{
BusyIndicator = false;
if (e.Success)
{
}
if (CloseForm)
ReturnToHomePage();
else
{
LoadUsers();
OnUsersSaved();
}
};
BusyIndicator = true;
BusyMessage = "Saving...";
_dataService.UpdateUsers(Database.CurrentProject.ProjectID, Database.CurrentClient.ClientID, _UpdatedUsers, _DeletedProjectUsers);
}
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