如何刷新MVVM WPF中的UI

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.

我已经构建了一个显示我的文件系统的树视图。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，因此在操作运行时，有一个禁用的按钮，在操作结束时我启用按钮。

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（如鼠标单击）以查看启用的按钮。

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 ViewModel I 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.

在我执行鼠标单击或任何击键后，UI更新就会发生。

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？

3 个解决方案

#1

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

您可以调整控件绑定模式TwoWay并使用PropertyChanged定义触发器

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

#2

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。我尝试了一切没有成功，最终我发现了这个线程：刷新WPF命令

I have used CommandManager.InvalidateRequerySuggested()

我用过CommandManager.InvalidateRequerySuggested（）

And its works.

它的作品。

Thanks for your help

谢谢你的帮助

#3

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以发送消息来更新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
}

#1