根据ViewModel属性更改画笔

本文介绍了根据ViewModel属性更改画笔的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

我有一个具有CarViewModel + view(UserControl)的应用程序. 我想要实现的是在绑定的DataContext Car.Status更改时更改画笔的样式.

I have an application which has CarViewModel + view (UserControl). What I want to achieve is to change the style of brushes when the bound DataContext Car.Status changes.

我发现了如何更改画笔(在视图后面的代码中):

I found out how to change the brushes (in code behind of the view):

private void LoadThemeResources(bool isPrepareMode) { if (isPrepareMode) { Uri themeUri = new Uri(@"/../Resources/MyBrushes.Light.xaml", UriKind.Relative); ResourceDictionary themeDictionary = Application.LoadComponent(themeUri) as ResourceDictionary; this.Resources.MergedDictionaries.Add(themeDictionary); } else { this.Resources.MergedDictionaries.Clear(); } }

默认情况下，应用程序和所有内容的深色主题分布在多个文件中.此MyBrushes.Light覆盖其中一些.

By default the application and everthing has a dark theme spread over multiple files. This MyBrushes.Light overwrites some of those.

但是我不知道如何以MVVM友好的方式基于ViewModel中的属性更改执行LoadThemeResources函数.

But I have no clue how I can execute the LoadThemeResources function based on a property change in the ViewModel in a MVVM friendly way.

我可以在视图背后的代码中完成

I can do in the code behind of the view:

var vm = (CarViewModel) DataContext; vm.Car.PropertyChanged += HandleStatusChanged;

但这是View和ViewModel之间的紧密耦合.

But this is a tight coupling between View and ViewModel.

我也可以通过Messenger(来自MVVM Light)来做到这一点，但这在整个应用程序中都被广播了，而且似乎有些过分.

I can also do it via Messenger (From MVVM Light), but that gets broadcasted throughout the whole application and seems overkill.

还有其他方法吗?还是首选方式?

Is there an other way? Or preferred way?

推荐答案

我将准备一些附加属性(在UserControl上使用).将该属性绑定到您的视图模型，并在更改后的属性回调中添加LoadThemeResources的代码逻辑，如下所示:

I would prepare some attached property (used on UserControl). Bind that property to your view-model and add code logic of LoadThemeResources in the property changed callback, something like this:

public static class ThemeService { public static DependencyProperty IsPrepareModeProperty = DependencyProperty.RegisterAttached("IsPrepareMode", typeof(bool), typeof(ThemeService), new PropertyMetadata(isPrepareModeChanged)); public static bool GetIsPrepareMode(UserControl e){ return (bool) e.GetValue(IsPrepareModeProperty); } public static void SetIsPrepareMode(UserControl e, bool value){ e.SetValue(IsPrepareModeProperty, value); } static void isPrepareModeChanged(object sender, DependencyPropertyChangedEventArgs e){ var u = sender as UserControl; u.LoadThemeResources((bool)e.NewValue); } } //you need some public method of LoadThemeResources public void LoadThemeResources(bool isPrepareMode) { //... }

在XAML中的使用 :

Usage in XAML:

<UserControl ... local:ThemeService.IsPrepareMode="{Binding Car.Status}"> <!-- ... --> </UserControl>

您还可以为UserControl的类声明一个普通的DependencyProperty，并使用它代替附加的属性(用法是相同的).

You can also declare a normal DependencyProperty for your UserControl's class and use that instead of the attached property (the usage is just the same).