wpf 点击按钮弹出新对话框_wpf-打开文件对话框MVVM
ViewModel不应打开对话框，甚至不知道它们的存在。 如果VM位于单独的DLL中，则该项目不应引用PresentationFramework。
我喜欢在视图中为常见对话框使用帮助器类。
helper类公开了XAML中窗口绑定到的命令(不是事件)。 这意味着在视图中使用RelayCommand。 助手类是DepencyObject，因此它可以绑定到视图模型。
class DialogHelper : DependencyObject
{
public ViewModel ViewModel
{
get { return (ViewModel)GetValue(ViewModelProperty); }
set { SetValue(ViewModelProperty, value); }
}
public static readonly DependencyProperty ViewModelProperty =
DependencyProperty.Register("ViewModel", typeof(ViewModel), typeof(DialogHelper),
new UIPropertyMetadata(new PropertyChangedCallback(ViewModelProperty_Changed)));
private static void ViewModelProperty_Changed(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
if (ViewModelProperty != null)
{
Binding myBinding = new Binding("FileName");
myBinding.Source = e.NewValue;
myBinding.Mode = BindingMode.OneWayToSource;
BindingOperations.SetBinding(d, FileNameProperty, myBinding);
}
}
private string FileName
{
get { return (string)GetValue(FileNameProperty); }
set { SetValue(FileNameProperty, value); }
}
private static readonly DependencyProperty FileNameProperty =
DependencyProperty.Register("FileName", typeof(string), typeof(DialogHelper),
new UIPropertyMetadata(new PropertyChangedCallback(FileNameProperty_Changed)));
private static void FileNameProperty_Changed(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
Debug.WriteLine("DialogHelper.FileName = {0}", e.NewValue);
}
public ICommand OpenFile { get; private set; }
public DialogHelper()
{
OpenFile = new RelayCommand(OpenFileAction);
}
private void OpenFileAction(object obj)
{
OpenFileDialog dlg = new OpenFileDialog();
if (dlg.ShowDialog() == true)
{
FileName = dlg.FileName;
}
}
}
helper类需要对ViewModel实例的引用。 请参阅资源字典。 在构造之后，就设置了ViewModel属性(在XAML的同一行中)。 这是当帮助程序类的FileName属性绑定到视图模型上的FileName属性时。
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-namespace:DialogExperiment"
xmlns:vm="clr-namespace:DialogExperimentVM;assembly=DialogExperimentVM"
Title="MainWindow" Height="350" Width="525">