[英]Implement Service Layer in WPF application
我正在研究WPF应用程序及其新功能,所以这可能是一个愚蠢的问题,
我想做的是从服务层触发绑定。 为了更好地解释,我创建了一个示例。 在此示例中,我想将WPF屏幕上的已记录消息(来自service方法)绑定到网格。
请参阅Service类中ServiceMethod中的我的评论。 这是我想触发绑定的地方。
我试图以最好的方式进行解释,但是如果您需要进一步的说明,请不要犹豫。
XAML
<Window x:Class="WpfApp1.ServiceExample"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:local="clr-namespace:WpfApp1"
mc:Ignorable="d"
Title="ServiceExample" Height="300" Width="300">
<Window.Resources>
<local:ServiceExampleViewModel x:Key="serviceExampleViewModel"></local:ServiceExampleViewModel>
</Window.Resources>
<Grid>
<StackPanel Orientation="Vertical">
<DataGrid ItemsSource="{Binding MessageLog,
Source={StaticResource serviceExampleViewModel},
Mode=TwoWay,
UpdateSourceTrigger=PropertyChanged}">
</DataGrid>
<Button Content="Call Service" Command="{Binding CallService,
Mode=TwoWay, Source={StaticResource serviceExampleViewModel}}"></Button>
<Label Content="{Binding ServiceResult,
Source={StaticResource serviceExampleViewModel},
Mode=TwoWay,
UpdateSourceTrigger=PropertyChanged}"></Label>
</StackPanel>
</Grid>
</Window>
服务实例
public partial class ServiceExample : Window
{
public ServiceExample()
{
InitializeComponent();
}
}
btnClick
public class btnClick : System.Windows.Input.ICommand
{
private Action WhatToExecute;
private Func<bool> WhenToExecute;
public btnClick(Action what, Func<bool> when)
{
WhatToExecute = what;
WhenToExecute = when;
}
public void Refresh()
{
if (this.CanExecuteChanged != null)
{
CanExecuteChanged(this, EventArgs.Empty);
}
}
public event EventHandler CanExecuteChanged;
public bool CanExecute(object parameter)
{
return WhenToExecute();
}
public void Execute(object parameter)
{
WhatToExecute();
}
}
ServiceExampleViewModel
class ServiceExampleViewModel : System.ComponentModel.INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
private int serviceResult;
public int ServiceResult
{
get { return serviceResult; }
set
{
serviceResult = value;
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs("ServiceResult"));
}
}
public btnClick CallService { get; set; }
public Service ServiceObj { get; set; }
public ServiceExampleViewModel()
{
ServiceObj = new Service();
this.CallService = new btnClick(CallServiceMethod, () => { return true; });
}
private void CallServiceMethod()
{
this.ServiceResult = this.ServiceObj.ServiceMethod();
}
}
信息
class Message
{
public string Text { get; set; }
}
服务
class Service
{
public List<Message> MessageLog;
public Service()
{
this.MessageLog = new List<Message>();
}
public int ServiceMethod()
{
int result = 0;
for (int counter = 0; counter < 10; ++counter)
{
//This is where binding should trigger
this.MessageLog.Add(new Message() { Text = string.Format("{0}:{1}", DateTime.Now.Ticks, counter) });
result += counter;
}
return result;
}
}
在MVVM中,您永远不会有来自服务的绑定。 服务的目的是成为数据的管道,其中可能包含一些有限的业务逻辑。 服务的寿命可能很短,并且通常不维护任何状态。
您的绑定应该在视图和视图模型之间,以任何其他方式绑定都违反了模式。
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