如何在 MVVM WPF 中刷新 UI

How can I refresh the UI in MVVM WPF

提问by Ofir

My project is based on the MVVM pattern.

我的项目基于 MVVM 模式。

I have built a tree view that shows my file system. Each folder has a checkbox for selecting the current folder. The selection process is taking some time so, while the operation runs, there is a button which is disabled and at the end of the operation I`m enabling the button.

我已经构建了一个树视图来显示我的文件系统。每个文件夹都有一个用于选择当前文件夹的复选框。选择过程需要一些时间，所以在操作运行时，有一个按钮被禁用，在操作结束时我启用了该按钮。

My problem is that when the button gets "disabled" I see it immediately. However, when the button is going back to the enabled mode I must do some action (like mouse click) to see the button enabled.

我的问题是，当按钮被“禁用”时，我会立即看到它。但是，当按钮返回启用模式时，我必须执行一些操作（例如鼠标单击）才能看到按钮启用。

How can I make sure that the UI will be updated immediately after the button is enabled?

如何确保在启用按钮后立即更新 UI？

These are my buttons:

这些是我的按钮：

<Button Content="&lt;- Back" Margin="5,0,5,0" Width="80" Height="25"
        IsEnabled="{Binding CanMoveToPreviousPage, UpdateSourceTrigger=PropertyChanged}" 
        Command="{Binding Path=NavigateBackCommand, IsAsync=True}" />

<Button Content="{Binding ButtonNextCaption}" Margin="5,0,5,0" Width="80" Height="25"
        IsEnabled="{Binding CanMoveToNextPage, UpdateSourceTrigger=PropertyChanged}" 
        Command="{Binding Path=NavigateNextCommand, IsAsync=True}" />

In my ViewModelI added this code:

在我的ViewModel 中，我添加了以下代码：

public bool CanMoveToNextPage
{
    get
    {
        return this.CurrentPage != null && this.CurrentPage.CanMoveNext;
    }
    set
    {
        if (CurrentPage != null)
        {
            this.CurrentPage.CanMoveNext = value;
            OnPropertyChanged("CanMoveToNextPage");
        }
    }
}

public bool CanMoveToPreviousPage
{
    get { return 0 < this.CurrentPageIndex && CurrentPage.CanMoveBack; }
    set
    {
        if (CurrentPage != null)
        {
            this.CurrentPage.CanMoveBack = value;
            OnPropertyChanged("CanMoveToPreviousPage");
        }
    }
}

The UI update happens just after I execute a mouse click or any keystroke.

UI 更新发生在我执行鼠标单击或任何击键之后。

This is the code of the action that is disabling and enabling the buttons:

这是禁用和启用按钮的操作代码：

void bg_RunWorkerCompleted(object sender, System.ComponentModel.RunWorkerCompletedEventArgs e)
{
    DecrementDoneCounter();
    if (ThreadSafeCouner == 0)//means all bg workers are done
    {
        UIlimitation(true);
    }
}

private int ThreadSafeCouner; // check how many bgworkers run
public void IncrementDoneCounter() { Interlocked.Increment(ref ThreadSafeCouner); }
public void DecrementDoneCounter() { Interlocked.Decrement(ref ThreadSafeCouner); }


void bg_DoWork(object sender, System.ComponentModel.DoWorkEventArgs e)
{
    IncrementDoneCounter();
    UIlimitation(false);
    ((bgArguments)e.Argument).SelectedDirectory.CanSelected = false;
    MarkItems(((bgArguments)e.Argument).SelectedDirectory, ((bgArguments)e.Argument).IsSelect);
    ((bgArguments)e.Argument).FreeWorkerAllocation();
    ((bgArguments)e.Argument).SelectedDirectory.CanSelected = true;
}

//this is the enabling action which execute the propeties setters at the upper part of this post
private static void UIlimitation(bool limit)
{
    MainWindowViewModel.Instance.CanMoveToNextPage = limit;
    MainWindowViewModel.Instance.CanMoveToPreviousPage = limit;
}

What can I do?

我能做什么？

回答by Aghilas Yakoub

You can adjust on your control Binding mode TwoWayand define triggers with PropertyChanged

您可以调整您的控件 Binding mode TwoWay并定义triggers with PropertyChanged

{Binding ElementName=.., Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}

回答by Ofir

OK I found a solution.
I tried everything without success and eventually I found this thread: Refresh WPF Command

好的，我找到了解决方案。
我尝试了一切都没有成功，最终我找到了这个线程： 刷新 WPF 命令

I have used CommandManager.InvalidateRequerySuggested()

我用过了 CommandManager.InvalidateRequerySuggested()

And its works.

和它的作品。

Thanks for your help

谢谢你的帮助

回答by sfogle

Here's a code example of how you might set up your ViewModel with the INotifyPropertyChanged method of sending messages to update the UI:

下面是一个代码示例，说明如何使用 INotifyPropertyChanged 方法设置 ViewModel 以发送消息以更新 UI：

public class MyViewModel : INotifyPropertyChanged
{
    /******************************************************/
    /* Property that you have created two-way binding for */
    /******************************************************/
    private double _myProperty
    public double MyProperty
    {
        get { return _myProperty; }
        set
        {
            _myProperty = value;

            OnNotifyPropertyChanged("MyProperty");
        }
    }

    #region INotifyPropertyChanged Members

    public event PropertyChangedEventHandler PropertyChanged;

    protected void OnNotifyPropertyChanged(string propertyName)
    {
        if (PropertyChanged != null)
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
    }

    #endregion INotifyPropertyChanged Members
}