将WPF命令绑定到C＃XAML中的ViewModel属性 [英] Bind WPF Command to ViewModel property in C# XAML
问题描述
我正在尝试构建通用的 Command ，该命令可以从我的 ViewModel 访问属性。在我的窗口上有几个 TextBoxes ，每个 TextBox 都有一个 Button 旁边。单击按钮时，我显示 OpenFileDialog 并设置 Text TextBox 的c>到所选文件的路径。 TextBox 本身对 ViewModel Binding >。当前，这是通过 ViewModel 中的 Command 实现的。 按钮都调用相同的命令，但是每个按钮具有其属性 CommandParameter 设置为将接收文件路径的 TextBox 。这样做的缺点是，我需要将参数从 Command execution强制转换为 TextBox ，然后设置其文本属性。现在的问题是，如果我无法以某种方式将我的命令绑定到绑定到 TextBox 的同一属性。这是我当前正在执行的操作：
I'm trying to build a generic Command that can access properties from my ViewModel. On my Window are several TextBoxes, each TextBoxhas a Button next to it. When the Button is clicked I show an OpenFileDialog and set the Text of the TextBox to the selected files path. The TextBoxitself has a Binding to a property in the ViewModel. Currently this is implemented with a Command in the ViewModel. The Buttons all call the same Commandbut each Button has a its property CommandParameter set to the TextBox that will receive the filepath. The drawback of this is, that I need to cast the parameter from the Commandexecution to a TextBox and then set its Textproperty. My question is now, if I can't somehow bind my 'Command' to the same property the TextBoxis bound to. Here is what I currently do:
XAML
<TextBox Text="{Binding SettingsPath}" x:Name="txtSettingsPath"></TextBox>
<Button Command="{Binding OpenFile}"
CommandParameter="{Binding ElementName=txtSettingsPath}">...</Button>
C＃
public ICommand OpenFile
{
get
{
bool CanExecuteOpenFileCommand()
{
return true;
}
CommandHandler GetOpenFileCommand()
{
return new CommandHandler((o) =>
{
OpenFileDialog ofd = new OpenFileDialog();
ofd.Multiselect = false;
if (!string.IsNullOrEmpty(SettingsPath) && File.Exists(settingsPath))
{
ofd.InitialDirectory = Path.GetDirectoryName(SettingsPath);
}
if(ofd.ShowDialog() == true)
{
if(o is TextBox txt)
{
txt.Text = ofd.FileName;
}
}
}, CanExecuteOpenFileCommand);
}
return GetOpenFileCommand();
}
}
在XAML中，我想要这样的东西：
In the XAML I would like to have something like this:
<TextBox Text="{Binding SettingsPath}"></TextBox>
<Button Command="{Binding OpenFile}"
CommandParameter="{Binding SettingsPath}">...</Button>
推荐答案
以下是我在评论中谈论的内容：
Here's what I was talking about in comments:
小视图模型。我添加了 Label 属性，因为在我的测试项目中，它们看起来都一样。这不一定是该视图模型的一部分。
The "little viewmodel". I added a Label property because in my test project, they all looked the same. That doesn't have to be part of this viewmodel.
public class SettingsPathSelectorViewModel : ViewModelBase
{
#region Label Property
private String _label = default(String);
public String Label
{
get { return _label; }
set
{
if (value != _label)
{
_label = value;
OnPropertyChanged();
}
}
}
#endregion Label Property
#region SettingsPath Property
private String _settingsPath = null;
public String SettingsPath
{
get { return _settingsPath; }
set
{
if (value != _settingsPath)
{
_settingsPath = value;
OnPropertyChanged();
}
}
}
#endregion SettingsPath Property
public ICommand OpenFile
{
get
{
bool CanExecuteOpenFileCommand()
{
return true;
}
// We're no longer using the parameter, since we now have one
// command per SettingsPath.
CommandHandler GetOpenFileCommand()
{
return new CommandHandler((o) =>
{
OpenFileDialog ofd = new OpenFileDialog();
ofd.Multiselect = false;
if (!string.IsNullOrEmpty(SettingsPath) && System.IO.File.Exists(SettingsPath))
{
ofd.InitialDirectory = System.IO.Path.GetDirectoryName(SettingsPath);
}
if (ofd.ShowDialog() == true)
{
SettingsPath = ofd.FileName;
}
}, o => CanExecuteOpenFileCommand());
}
return GetOpenFileCommand();
}
}
}
演示的快捷工具主视图模型目的。我们将说明两种不同的方式来公开这些内容：要么作为命名属性，要么在 ItemsControl 中显示为不同大小的集合。
A quickie main viewmodel for demo purposes. We'll illustrate two different ways you could expose these things: Either as named properties, or a collection of varying size displayed in an ItemsControl.
public class MainViewModel : ViewModelBase
{
public SettingsPathSelectorViewModel FirstPath { get; } = new SettingsPathSelectorViewModel() { Label = "First Path" };
public SettingsPathSelectorViewModel SecondPath { get; } = new SettingsPathSelectorViewModel() { Label = "Second Path" };
public ObservableCollection<SettingsPathSelectorViewModel> SettingsPaths { get; } = new ObservableCollection<SettingsPathSelectorViewModel>
{
new SettingsPathSelectorViewModel() { Label = "First Collection Path" },
new SettingsPathSelectorViewModel() { Label = "Second Collection Path" },
new SettingsPathSelectorViewModel() { Label = "Third Collection Path" },
};
}
XAML：
<Window.Resources>
<DataTemplate DataType="{x:Type local:SettingsPathSelectorViewModel}">
<!-- GroupBox and Label are optional -->
<GroupBox Header="{Binding Label}">
<StackPanel Orientation="Horizontal">
<TextBox Text="{Binding SettingsPath}" />
<Button
Content="..."
Command="{Binding OpenFile}"
HorizontalAlignment="Left"
MinWidth="40"
Margin="4,0,0,0"
/>
</StackPanel>
</GroupBox>
</DataTemplate>
</Window.Resources>
<Grid>
<StackPanel Orientation="Vertical">
<StackPanel Orientation="Horizontal">
<ContentControl Content="{Binding FirstPath}" />
<ContentControl Content="{Binding SecondPath}" />
</StackPanel>
<ItemsControl
ItemsSource="{Binding SettingsPaths}"
/>
</StackPanel>
</Grid>
这就是我删除 Label 的意思。 GroupBox ：
Here's what I mean about omitting Label and the GroupBox:
<Window.Resources>
<DataTemplate DataType="{x:Type local:SettingsPathSelectorViewModel}">
<StackPanel Orientation="Horizontal">
<TextBox Text="{Binding SettingsPath}" />
<Button
Content="..."
Command="{Binding OpenFile}"
HorizontalAlignment="Left"
MinWidth="40"
Margin="4,0,0,0"
/>
</StackPanel>
</DataTemplate>
</Window.Resources>
<Grid>
<StackPanel Orientation="Vertical">
<Label>First Path</Label>
<ContentControl Content="{Binding FirstPath}" />
<Label>Second Path</Label>
<ContentControl Content="{Binding SecondPath}" />
</StackPanel>
</Grid>
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