如何使用 MVVM 将焦点设置为 WPF 控件？
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How to set Focus to a WPF Control using MVVM?
提问by user2519971
I am validating user input in my viewmodel and throwing validation message in case validation fails for any of values.
我正在我的视图模型中验证用户输入并抛出验证消息，以防任何值的验证失败。
I just need to set the focus to the particular control for which validation has failed.
我只需要将焦点设置为验证失败的特定控件。
Any idea how to achieve this ?
知道如何实现这一目标吗？
回答by Sheridan
Generally, when we want to use a UI event while adhering to the MVVM methodology, we create an Attached Property:
通常，当我们想要在坚持 MVVM 方法的同时使用 UI 事件时，我们会创建一个Attached Property：
public static DependencyProperty IsFocusedProperty = DependencyProperty.RegisterAttached("IsFocused", typeof(bool), typeof(TextBoxProperties), new UIPropertyMetadata(false, OnIsFocusedChanged));
public static bool GetIsFocused(DependencyObject dependencyObject)
{
return (bool)dependencyObject.GetValue(IsFocusedProperty);
}
public static void SetIsFocused(DependencyObject dependencyObject, bool value)
{
dependencyObject.SetValue(IsFocusedProperty, value);
}
public static void OnIsFocusedChanged(DependencyObject dependencyObject, DependencyPropertyChangedEventArgs dependencyPropertyChangedEventArgs)
{
TextBox textBox = dependencyObject as TextBox;
bool newValue = (bool)dependencyPropertyChangedEventArgs.NewValue;
bool oldValue = (bool)dependencyPropertyChangedEventArgs.OldValue;
if (newValue && !oldValue && !textBox.IsFocused) textBox.Focus();
}
This property is used like this:
这个属性是这样使用的：
<TextBox Attached:TextBoxProperties.IsFocused="{Binding IsFocused}" ... />
Then we can focus the TextBoxfrom the view model by changing the IsFocusedproperty to true:
然后我们可以TextBox通过将IsFocused属性更改为来关注视图模型true：
IsFocused = false; // You may need to set it to false first if it is already true
IsFocused = true;
