Open File Dialog MVVM

Question

Ok I really would like to know how expert MVVM developers handle an openfile dialog in WPF.

I don't really want to do this in my ViewModel(where 'Browse' is referenced via a DelegateCommand)

    void Browse(object param)
    {
        //Add code here
        OpenFileDialog d = new OpenFileDialog();


        if (d.ShowDialog() == true)
        {
            //Do stuff
        }
    }

Because I believe that goes against MVVM methodology.

What do I do?

Answer 1

The best thing to do here is use a service.

A service is just a class that you access from a central repository of services, often an IOC container. The service then implements what you need like the OpenFileDialog.

So, assuming you have an IFileDialogService in a Unity container, you could do...

void Browse(object param)
{
    var fileDialogService = container.Resolve<IFileDialogService>();

    string path = fileDialogService.OpenFileDialog();

    if (!string.IsNullOrEmpty(path))
    {
        //Do stuff
    }
}

Answer 2

I use a service which i for example can pass into the constructor of my viewModel or resolve via dependency injection. e.g.

public interface IOpenFileService
{
    string FileName { get; }
    bool OpenFileDialog()
}

and a class implementing it, using OpenFileDialog under the hood. In the viewModel, i only use the interface and thus can mock/replace it if needed.

Answer 3

Having a service is like opening up a view from viewmodel. I have a Dependency property in view, and on the chnage of the property, I open up FileDialog and read the path, update the property and consequently the bound property of the VM