如何在WPF MVVM中将View变量绑定到ViewModel？

Question

I have a created a window ( WPF and MVVM ) - say PrintWidow ( so I have PrintWindow.xaml , PrintWindow.xaml.cs , PrintWindowViewModel.cs- viewmodel)

Now I am going to use(call) this PrintWindow obj from some other class on button click or on some command trigger , I want to set Document Source for this PrintWindow(following MVVM).

How would I do this ? I created a PrintDocument object in PrintWindow.xaml.cs and tried to bind it as follows : (obviously just a blank try - as I cannot do this declaration in XAML)

private PrintDocument printDocuementView;

public PrintDocument PrintDocuement
{
    get { return printDocuementView; }
    set { printDocuementView = value; }
}

//constructor
public PrintWindow()
{
    InitializeComponent();
    this.DataContext = new PrintViewModel();

    Binding b = new Binding();
    b.Source = printDocuementView;
    b.Path = new PropertyPath("PrintDocumentCommand"); // "PrintDocumentCommand" is defined in View Model class and is responsible to set the `PrintDocument` object there.

}

This code (obviously) doesn't work. How should I go about it. Summary : I want to open PrintWindow from another window and eventually set some Property of PrintWindow from code behind of the 'other widow' object.The query is - where should this property go? View ? ViewModel? ?? puzzzeled

I have googled for answers - but couldn't relate any to my problem.

I am a Freshman for WPF and a Rookie for MVVM .

Answer 1

Since your PrintDocumentCommand is in your PrintViewModel but you're setting the Source of this Binding to an instance of the PrintDocument -Class, it can't be found, because the Binding is looking for the PrintDocumentCommand in PrintDocument -Class.

If you want to open the PrintWindow from another Window, place the PrintDocument -Property and the PrintDocumentCommand in the ViewModel of the other Window. Now your function that is executed through the PrintDocumentCommand could look like:

private void Print()
{
    PrintWindow pw = new PrintWindow(PrintDocument);
    pw.ShowDialog();
}

The constructor of your PrintView could be like:

public PrintWindow(PrintDocument pd)
{
    InitializeComponents();
    this.DataContext = new PrintViewModel(pd);
}

and now you can access the PrintDocument in your PrintViewModel.