Presentation Model (MVVM) Good Practices

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using PresentationModelBase;
using Microsoft.Win32;

namespace App.Configuration.Wpf
{
    class WpfDialogSystem : IDialogSystem
    {
        #region IDialogServicesProvider Members

        public QuestionResult AskQuestion(string question)
        {
            return AskQuestion(question, "Question");
        }

        public QuestionResult AskQuestion(string question, string title)
        {
            var result = System.Windows.MessageBox.Show(question, title, System.Windows.MessageBoxButton.YesNo, System.Windows.MessageBoxImage.Question);
            switch (result)
            {
                case System.Windows.MessageBoxResult.Yes:
                    return QuestionResult.Yes;
                default:
                    return QuestionResult.No;
            }
        }

        public System.IO.FileInfo ChooseFile(string title, string filter)
        {
            OpenFileDialog dialog = new OpenFileDialog();
            dialog.Title = title;
            dialog.Filter = filter;
            dialog.ShowDialog();
            if (dialog.FileName != null && dialog.FileName.Trim() != string.Empty)
                return new System.IO.FileInfo(dialog.FileName);
            return null;
        }

        public System.IO.FileInfo ChooseImage()
        {
            return ChooseImage("");
        }

        public System.IO.FileInfo ChooseImage(string title)
        {
            return ChooseFile(title, "Image Files (*.bmp, *.jpg, *.jpeg, *.png)|*.bmp;*.jpg;*.jpeg;*.png");
        }

        #endregion
    }
}