从视图模型打印WPF视觉

Question

如何通过调用打印方法来打印视图或窗口，而不使用如本示例中所示的RelayCommand进行打印：Print WPF Visuals with MVVM pattern？

var printDlg = new PrintDialog(); 
printDlg.PrintVisual(View, "JOB PRINTING") 

Answer 1

好吧，这是一个快速，肮脏但可重复使用的附加行为类。 免责声明：我只是在几分钟之内就砍掉了它，它有缺陷，应该很容易克服。

首先我们需要我们的服务类。

public class VisualPrinter 
{ 
    private static RoutedUICommand PrintVisualCommand = new RoutedUICommand("PrintVisualCommand", "PrintVisualCommand", typeof(VisualPrinter)); 

    #region ab PrintCommand 

    public static ICommand GetPrintCommand(DependencyObject aTarget) 
    { 
     return (ICommand)aTarget.GetValue(PrintCommandProperty); 
    } 

    public static void SetPrintCommand(DependencyObject aTarget, ICommand aValue) 
    { 
     aTarget.SetValue(PrintCommandProperty, aValue); 
    } 

    public static readonly DependencyProperty PrintCommandProperty = 
     DependencyProperty.RegisterAttached("PrintCommand", typeof(ICommand), typeof(VisualPrinter), new FrameworkPropertyMetadata(PrintVisualCommand)); 

    #endregion 

    #region ab EnablePrintCommand 

    public static bool GetEnablePrintCommand(DependencyObject aTarget) 
    { 
     return (bool)aTarget.GetValue(EnablePrintCommandProperty); 
    } 
    public static void SetEnablePrintCommand(DependencyObject aTarget, bool aValue) 
    { 
     aTarget.SetValue(EnablePrintCommandProperty, aValue); 
    } 

    public static readonly DependencyProperty EnablePrintCommandProperty = 
     DependencyProperty.RegisterAttached("EnablePrintCommand", typeof(bool), typeof(VisualPrinter), new FrameworkPropertyMetadata(false, OnEnablePrintCommandChanged)); 

    private static void OnEnablePrintCommandChanged(DependencyObject aDependencyObject, DependencyPropertyChangedEventArgs aArgs) 
    { 
     var newValue = (bool)aArgs.NewValue; 
     var element = aDependencyObject as UIElement; 
     if(newValue) 
     { 
      element.CommandBindings.Add(new CommandBinding(PrintVisualCommand, OnPrintVisual)); 
     } 
    } 

    private static void OnPrintVisual(object aSender, ExecutedRoutedEventArgs aE) 
    { 
     // the element is the one were you set the EnablePrintCommand 
     var element = aSender as Visual; 
     var printDlg = new PrintDialog(); 
     // do the printing 
    } 

    #endregion 
} 

这里我们定义两个附加属性。 PrintCommand用于将实际的打印命令注入视图模型，这必须使用OneWayToSource完成。 第二个是EnablePrintCommand，用于启用打印，设置应打印哪个元素并注册命令绑定。

我目前的版本有一个缺陷，即你不能在同一个元素上设置两个属性，但这很容易被克服。因此，要打印的按钮，它看起来像这样：

<Grid local:VisualPrinter.EnablePrintCommand="True"> 
    <Button Content="Test" local:VisualPrinter.PrintCommand="{Binding ViewModelPrint, Mode=OneWayToSource"> 
</Grid> 

虽然ViewModelPrint是类型的ICommand的视图中的模型，其可以被执行，并且然后将打印网格（因此的按钮）的性质。