blocks|key|2414327|text|要做到这一点，最简单的方法是在代码背后，尽管这对WPF开发人员来说有点福克斯通行证，但它是视图逻辑，不会破坏单元测试的可能性。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2414328|++++<TextBox+GotFocus="GotFocus"/>
++++<Button+Name="SaveButton"+Command="{Binding+SaveCommand}"+IsEnabled="False">
++++++++<TextBlock+Text="Save"/>
++++</Button>|code-block|syntax|javascript|2414329|然后|2414330|++++private+void+GotFocus(+object+sender,+RoutedEventArgs+e+)
++++{
++++++++SaveButton.IsEnabled+=+true;
++++}|2414331|或者，您可以将一个命令附加到GotFocus事件(http://stackoverflow.com/questions/1048517/wpf-calling-commands-via-events)，在视图模型上设置一个布尔值，该布尔值也是在"SaveCommand“CanExecute方法中查询的。|offset|length|2414332|entityMap|0|LINK|mutability|MUTABLE|url|http://stackoverflow.com/questions/1048517/wpf-calling-commands-via-events^0|0|0|0|0|P|22|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|X|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Y|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|Z|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|10|8|@]|9|@$M|11|N|12|1|13]]|A|$]]|$1|O|3|-4|5|6|7|14|8|@]|9|@]|A|$]]]|P|$Q|$5|R|S|T|A|$U|V]]]]

<p>The easiest way to do this is in the codebehind, although this is a bit of a foux pas with WPF developers, it is view logic and will not destroy unit testing possibilities.</p>

<pre><code>    &lt;TextBox GotFocus="GotFocus"/&gt;
    &lt;Button Name="SaveButton" Command="{Binding SaveCommand}" IsEnabled="False"&gt;
        &lt;TextBlock Text="Save"/&gt;
    &lt;/Button&gt;
</code></pre>

<p>then</p>

<pre><code>    private void GotFocus( object sender, RoutedEventArgs e )
    {
        SaveButton.IsEnabled = true;
    }
</code></pre>

<p>alternatively you could attach a command to the GotFocus event (http://stackoverflow.com/questions/1048517/wpf-calling-commands-via-events) setting a boolean on the viewmodel which is also queried in the "SaveCommand" CanExecute method.</p>


blocks|key|3596907|text|听起来您想要将属性命名为IsDirty，并且仅在模型变脏时才使保存按钮可用。您可以在视图模型上使用CanSave属性，该属性在加载模型时将新模型值与原始值进行比较，例如：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3596908|public+bool+CanSave
{
++get
++{
++++return+this.IsDirty;+++++
++}
}

public+bool+IsDirty
{
++get
++{
++++if+(this.ModelPropertyValue+!=+this.ModelOriginalPropertyValue)
++++{
++++++return+true;++
++++}

++++return+false;
++}
}

private+string+modelPropertyValue;
public+string+ModelPropertyValue
{
++get
++{
++++return+this.modelPropertyValue;
++}

++set
++{
++++if+(this.modelPropertyValue+==+value)+
++++{
++++++return;
++++}

++++this.modelPropertyValue+=+value;
++++OnPropertyChanged(()+=>+this.ModelPropertyValue);
++++OnPropertyChanged(()+=>+this.CanSave);
++}
}|code-block|syntax|javascript|3596909|默认情况下，文本框仅在失去焦点时更新其绑定属性，因此您需要在文本框上设置UpdateSourceTrigger属性：|3596910|<TextBox+Text="{Binding+ModelPropertyValue,+UpdateSourceTrigger=PropertyChanged}"+/>
<Button+IsEnabled="{Binding+CanSave}">Save</Button>|3596911|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

<p>It sounds like you want to name your property IsDirty, and only make the Save button available if the model has become dirty.  You could have a CanSave property on your view model which checks the new model value against the original value when the model was loaded, e.g: </p>

<pre><code>public bool CanSave
{
  get
  {
    return this.IsDirty;     
  }
}

public bool IsDirty
{
  get
  {
    if (this.ModelPropertyValue != this.ModelOriginalPropertyValue)
    {
      return true;  
    }

    return false;
  }
}

private string modelPropertyValue;
public string ModelPropertyValue
{
  get
  {
    return this.modelPropertyValue;
  }

  set
  {
    if (this.modelPropertyValue == value) 
    {
      return;
    }

    this.modelPropertyValue = value;
    OnPropertyChanged(() =&gt; this.ModelPropertyValue);
    OnPropertyChanged(() =&gt; this.CanSave);
  }
}
</code></pre>

<p>Textboxes by default only update their bound property on lost focus, so you will need to set the UpdateSourceTrigger property on your text box:</p>

<pre><code>&lt;TextBox Text="{Binding ModelPropertyValue, UpdateSourceTrigger=PropertyChanged}" /&gt;
&lt;Button IsEnabled="{Binding CanSave}"&gt;Save&lt;/Button&gt;
</code></pre>


blocks|key|3596945|text|您可以使用Commanding轻松实现这一点。如果您将ViewModel上的命令绑定到按钮，并且CanExecute方法从其他输入中查找有效信息，则它将保持禁用状态，直到满足该条件为止。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|3596946|在MVVM+Light中，它看起来像这样|3596947|public+RelayCommand+LogonCommand+{+get;+private+set;+}

LogonCommand+=+new+RelayCommand(
++++++++++++++++++++Logon,
++++++++++++++++++++CanLogon
++++++++++++++++);

private+Boolean+CanLogon(){
++++return+!String.IsNullOrWhiteSpance(SomeProperty);
}|code-block|syntax|javascript|3596948|在XAML中，只需确保将按钮命令绑定到ViewModel命令：|3596949|<Button+Command="{Binding+LogonCommand}"+/>|3596950|如果你的文本框被绑定到SomeProperty，这将不需要任何额外的工作，也没有必要的代码隐藏。|style|CODE|3596951|另外，如果您想使用这个trigger+on+property+change而不是LostFocus，那么您需要显式地定义它。|3596952|<TextBox>
++<TextBox.Text>
++++<Binding+Source="{StaticResource+myDataSource}"+Path="SomeProperty"
+++++++++++++UpdateSourceTrigger="PropertyChanged"/>
++</TextBox.Text>
</TextBox>|3596953|entityMap|0|LINK|mutability|MUTABLE|url|http://msdn.microsoft.com/en-us/library/ms752308.aspx|1|http://msdn.microsoft.com/en-us/library/system.windows.input.icommand.canexecute.aspx|2|http://www.galasoft.ch/mvvm/getstarted/|3|http://msdn.microsoft.com/en-us/library/system.windows.data.binding.updatesourcetrigger.aspx^0|5|A|0|1C|A|1|0|1|A|2|0|0|0|0|B|C|0|B|Q|3|0|0^^$0|@$1|2|3|4|5|6|7|1A|8|@]|9|@$A|1B|B|1C|1|1D]|$A|1E|B|1F|1|1G]]|C|$]]|$1|D|3|E|5|6|7|1H|8|@]|9|@$A|1I|B|1J|1|1K]]|C|$]]|$1|F|3|G|5|H|7|1L|8|@]|9|@]|C|$I|J]]|$1|K|3|L|5|6|7|1M|8|@]|9|@]|C|$]]|$1|M|3|N|5|H|7|1N|8|@]|9|@]|C|$I|J]]|$1|O|3|P|5|6|7|1O|8|@$A|1P|B|1Q|Q|R]]|9|@]|C|$]]|$1|S|3|T|5|6|7|1R|8|@]|9|@$A|1S|B|1T|1|1U]]|C|$]]|$1|U|3|V|5|H|7|1V|8|@]|9|@]|C|$I|J]]|$1|W|3|-4|5|6|7|1W|8|@]|9|@]|C|$]]]|X|$Y|$5|Z|10|11|C|$12|13]]|14|$5|Z|10|11|C|$12|15]]|16|$5|Z|10|11|C|$12|17]]|18|$5|Z|10|11|C|$12|19]]]]

<p>You can easily accomplish this using <a href="http://msdn.microsoft.com/en-us/library/ms752308.aspx" rel="nofollow">Commanding</a>. If you bind a command on your ViewModel to your button, and the <a href="http://msdn.microsoft.com/en-us/library/system.windows.input.icommand.canexecute.aspx" rel="nofollow">CanExecute</a> method looks for valid info from your other inputs, then it will stay disabled until that condition is met.</p>

<p>In <a href="http://www.galasoft.ch/mvvm/getstarted/" rel="nofollow">MVVM Light</a> it would look something like this</p>

<pre><code>public RelayCommand LogonCommand { get; private set; }

LogonCommand = new RelayCommand(
                    Logon,
                    CanLogon
                );

private Boolean CanLogon(){
    return !String.IsNullOrWhiteSpance(SomeProperty);
}
</code></pre>

<p>In your XAML just be sure to bind the button command to the ViewModel command:</p>

<pre><code>&lt;Button Command="{Binding LogonCommand}" /&gt;
</code></pre>

<p>If your textbox is bound to <code>SomeProperty</code> this will work without any extra work, and no code behind necessary.</p>

<p>Also, if you want to have this <a href="http://msdn.microsoft.com/en-us/library/system.windows.data.binding.updatesourcetrigger.aspx" rel="nofollow">trigger on property change</a> instead of LostFocus, then you need to define that explicitly.</p>

<pre><code>&lt;TextBox&gt;
  &lt;TextBox.Text&gt;
    &lt;Binding Source="{StaticResource myDataSource}" Path="SomeProperty"
             UpdateSourceTrigger="PropertyChanged"/&gt;
  &lt;/TextBox.Text&gt;
&lt;/TextBox&gt;
</code></pre>


blocks|key|2414366|text|您将需要使用EventTrigger。实际上，有两个。一个用于GotFocus，另一个用于LostFocus事件。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2414367|下面是一个示例：|2414368|Using+EventTrigger+in+XAML+for+MVVM+–+No+Code+Behind+Code|2414369|查找SetProperty触发器操作。这对你很有用。|2414370|entityMap|0|LINK|mutability|MUTABLE|url|http://www.kunal-chowdhury.com/2010/11/using-eventtrigger-in-xaml-for-mvvm-no.html^0|6|C|V|8|19|9|0|0|0|1L|0|0|2|B|0^^$0|@$1|2|3|4|5|6|7|T|8|@$9|U|A|V|B|C]|$9|W|A|X|B|C]|$9|Y|A|Z|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|10|8|@]|D|@]|E|$]]|$1|H|3|I|5|6|7|11|8|@]|D|@$9|12|A|13|1|14]]|E|$]]|$1|J|3|K|5|6|7|15|8|@$9|16|A|17|B|C]]|D|@]|E|$]]|$1|L|3|-4|5|6|7|18|8|@]|D|@]|E|$]]]|M|$N|$5|O|P|Q|E|$R|S]]]]

<p>You will need to use an <code>EventTrigger</code>. Actually, two of them. One for <code>GotFocus</code> and other for <code>LostFocus</code> event.</p>

<p>Here is an example:</p>

<p><a href="http://www.kunal-chowdhury.com/2010/11/using-eventtrigger-in-xaml-for-mvvm-no.html" rel="nofollow">Using EventTrigger in XAML for MVVM – No Code Behind Code</a> </p>

<p>Look for <code>SetProperty</code> trigger action. That will be useful for you.</p>


blocks|key|5711648|text|如果你只有一个文本框，懒惰，快速和不那么优雅的解决方案：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|5711649|++++<TextBox+Name="TB"+Width="200"/>
++++<Button+Content="Save">
++++++++<Button.Style>
++++++++++++<Style+TargetType="Button">
++++++++++++++++<Style.Triggers>
++++++++++++++++++++<DataTrigger+Binding="{Binding+ElementName=TB,+Path=Text}"+Value="">
++++++++++++++++++++++++<Setter+Property="IsEnabled"+Value="False"/>
++++++++++++++++++++</DataTrigger>
++++++++++++++++</Style.Triggers>
++++++++++++</Style>
++++++++</Button.Style>
++++</Button>|code-block|syntax|javascript|5711650|该按钮将在文本框中有文本时立即启用。|5711651|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

<p>Lazy, quick and not so elegant solution if you only have one textbox:</p>

<pre><code>    &lt;TextBox Name="TB" Width="200"/&gt;
    &lt;Button Content="Save"&gt;
        &lt;Button.Style&gt;
            &lt;Style TargetType="Button"&gt;
                &lt;Style.Triggers&gt;
                    &lt;DataTrigger Binding="{Binding ElementName=TB, Path=Text}" Value=""&gt;
                        &lt;Setter Property="IsEnabled" Value="False"/&gt;
                    &lt;/DataTrigger&gt;
                &lt;/Style.Triggers&gt;
            &lt;/Style&gt;
        &lt;/Button.Style&gt;
    &lt;/Button&gt;
</code></pre>

<p>The button will be enabled as soon as there is text in the textbox.</p>


<p>I am looking for the correct syntax in my XAML to set a property in my Viewmodel (eg "BusyEditing"), which then has already been linked to the "IsEnabled" Binding of a button.
Basically, I want the "Save" button to be enabled as soon as I enter a field to begin editing it. What would be even cooler is if the property was updated on the CHANGE of the textbox value, and not just the GotFocus.</p>

<p>Thanks in advance.</p>


Update property in ViewModel when a control Gets Focus

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我在我的XAML中寻找正确的语法来设置我的视图模型中的属性(例如"BusyEditing")，然后它已经链接到按钮的"IsEnabled“绑定。基本上，我希望“保存”按钮在我输入一个字段开始编辑时立即启用。更酷的是，如果属性随着textbox值的更改而更新，而不仅仅是GotFocus。提前谢谢。

问当控件获得焦点时更新ViewModel中的属性
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问当控件获得焦点时更新ViewModel中的属性EN