Error of: Application' is an ambiguous reference between 'System.Windows.Application' and 'System.Windows.Forms.Application'

Question

I'm running this in Visual Studio 2013.

For Application.Current.Shutdown I get:

'Application' is an ambiguous reference between 'System.Windows.Application' and 'System.Windows.Forms.Application' .

I tried using using SystemInformation = System.Windows.Forms.SystemInformation; in place of using System.Windows.Forms as one site suggested but I get the error:

The type or namespace name 'OpenFileDialog' could not be found (are you missing a using directive or an assembly reference?) for the line OpenFileDialog dlg = new OpenFileDialog();

How can I fix it so I can use OpenFileDialog? I want an open file dialog box to appear.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Forms;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
using PTDGUI.View;  

private void mnuExit_Click(object sender, RoutedEventArgs e)
{
    Application.Current.Shutdown();
}

private void button1_Click(object sender, EventArgs e)
{
    OpenFileDialog dlg = new OpenFileDialog();
    dlg.ShowDialog();

    if (dlg.ShowDialog() == DialogResult.OK)
    {
       string fileName;
       fileName = dlg.FileName;
       MessageBox.Show(fileName);
    }
}

Answer 1

Try this to avoid ambiguity of Application class.

private void mnuExit_Click(object sender, RoutedEventArgs e)
{
    System.Windows.Application.Current.Shutdown();
}

Update

The reason for this ambiguity is both namespace System.Windows.Forms and System.Windows contains definition for class Application . so at this point c# compiler gets confused which implementation of Application to refer to.

If you are not referring any classes from System.Windows.Forms you can remove it from the list of using.