[英]Updating a TextBlock Binding
I'm working on a WP7 app and I've had some trouble updating a TextBlock
bound to a property. 我正在开发WP7应用程序,但在更新绑定到属性的
TextBlock
遇到了一些麻烦。 I'm new to MVVM, and C# in general, so I'm not sure what I'm doing wrong. 我是MVVM和C#的新手,所以我不确定自己做错了什么。
In the end I have solved this problem, but I don't understand why my solution works (always fun ...), so I'd really appreciate your guidance. 最后,我解决了这个问题,但是我不明白为什么我的解决方案有效(总是很有趣...),因此,我非常感谢您的指导。
In my app's Model, I originally had something like this: 在我的应用程序模型中,我最初有这样的东西:
// Broken
namespace MyApp.MyModel
{
public class MetaData : INotifyPropertyChanged
{
private StatusType status;
public StatusType Status
{
get { return status; }
set
{
status = value;
statusMessage = ConvertStatusToSomethingMeaningful(value);
}
}
private string statusMessage;
public string StatusMessage
{
get { return statusMessage; }
private set
{
statusMessage = value;
// This doesn't work
NotifyPropertyChanged("StatusMessage");
}
}
...
}
}
Status
is a enum
, and when it's set by my app, it also sets StatusMessage
too (which is a more human readable description to show the user). Status
是一个enum
,当由我的应用设置时,它也会同时设置StatusMessage
(这是更易于理解的描述,以向用户显示)。 My View's TextBlock
is bound to StatusMessage
, but it doesn't update using the above code. 我的视图的
TextBlock
绑定到StatusMessage
,但不会使用上述代码进行更新。
However, if I move NotifyPropertyChanged("StatusMessage")
into Status
, my View's TextBlock
updates like it should. 但是,如果我将
NotifyPropertyChanged("StatusMessage")
移到Status
,则我的View的TextBlock
像应该的那样进行更新。 However, I don't understand why this works when the original code above doesn't? 但是,我不明白为什么上面的原始代码不起作用,为什么这行得通?
// Fixed
namespace MyApp.MyModel
{
public class MetaData : INotifyPropertyChanged
{
private StatusType status;
public StatusType Status
{
get { return status; }
set
{
status = value;
StatusMessage = ConvertStatusToSomethingMeaningful(value);
// This works
NotifyPropertyChanged("StatusMessage");
}
}
public string StatusMessage { get; private set; }
...
}
}
Many thanks in advance for helping a newbie out :) 在此先感谢您帮助新手:)
Issue in this line: 此行中的问题:
statusMessage = ConvertStatusToSomethingMeaningful(value);
StatusMessage setter is never called (NotifyPropertyChanged("StatusMessage") called exactly there) 从不调用StatusMessage设置程序(确切地在其中调用NotifyPropertyChanged(“ StatusMessage”))
StatusMessage = ConvertStatusToSomethingMeaningful(value);
will be the right call 将是正确的选择
Probably my implementation of this would be next: 大概我的实现将是下一个:
namespace MyApp.MyModel
{
public class MetaData : INotifyPropertyChanged
{
private StatusType status;
public StatusType Status
{
get { return status; }
set
{
if (status != value)
{
status = value;
NotifyPropertyChanged("Status");
NotifyPropertyChanged("StatusMessage");
}
}
}
public string StatusMessage
{
get { return ConvertStatusToSomethingMeaningful(status); }
}
...
}
}
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