The other day someone asked if they could open the Windows system calculator from LightSwitch. Because it is Silverlight based, I thought there might be a challenge, however it is actually quite easy to do. Here is how…

I know that Microsoft Word can be accessed via some fancy Interop footwork, so I based my approach on that very same assumption that other stuff might be available via Interop. Here is how to get at the Windows Calculator via this interop magic…

First, I created a simple LightSwitch project. No tables, just the project. Then, in the Solution Explorer I go all code monkey and select to view the solution in File View…

Within the file view of the solution, I expand the Client project. I then right-click the Client project and select  to add a new class to the project…

In my example, I named the class file MyCalculator.cs (yes, I am doing C# this time ).

Here is what the class file looks like…

(C#)

using System;
using System.Net;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Ink;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Shapes;
using System.Runtime.InteropServices;
using System.Runtime.InteropServices.Automation;

namespace LightSwitchApplication
{
    public class MyCalculator
    {
        public static void ShowCalculator()
        {
           dynamic calc = AutomationFactory.CreateObject("WScript.Shell");
           calc.Run(@"%SystemRoot%\system32\calc.exe");
        }

    }
}

(VB.Net)

Imports System.Net
Imports System.Text
Imports System.Windows
Imports System.Windows.Controls
Imports System.Windows.Documents
Imports System.Windows.Ink
Imports System.Windows.Input
Imports System.Windows.Media
Imports System.Windows.Media.Animation
Imports System.Windows.Shapes
Imports System.Runtime.InteropServices
Imports System.Runtime.InteropServices.Automation

Namespace LightSwitchApplication
	Public Class MyCalculator
		Public Shared Sub ShowCalculator()
			Dim calc As dynamic = AutomationFactory.CreateObject("WScript.Shell")
			calc.Run("%SystemRoot%\system32\calc.exe")
		End Sub

	End Class
End Namespace

A couple of important thingies here. The first is the use of the System.Runtime.InteropServices namespace. It is via interop services that the magic will occur – which is what you can see being performed in the ShowCalculator method. Using the Windows Script Host object, the code simply runs a command line like call to fire up the calculator.

That is all that is really required.

Next, I go back to the solution explorer and select to view the solution in Logical View…

 In the logical view of the solution explorer, I right-click the Screens node and select to add a screen…

In my example, I am only trying to figure out how to open a calculator, so forget about adding any tables or fancy screens. I just want to say, “Hey, that is cool, and I did it!”.

So, in the Add New Screen dialog, I simply select to add a New Data Screen and click the OK button…

With my new screen, all I need is some way to call that handy method in the MyCalculator class of the Client project. To do that, I’ll add a button to the screen and then call some code from that button. So, I click the Add Data Item button on the top of the screen designer, and then add a Method screen member with a name of ShowCalculator, and then click the OK button.

In the screen designer, I drag and drop the ShowCalculator data item to the screen command bar…

All this work has made me hungry at this point. I leave my home office desk and slather some yummy peanut butter and jam between two slices of bread, nibble away and wash it down with a nice cold glass of milk. Mmmmm milk!

After cleaning the crumbs from my keyboard, I go back to the screen designer and right-click the newly added Show Calculator data item on the screen. In the resulting popup context menu, I click the Edit CanExecute Code item.

In the resulting code window, I first add a using statement that gets me access to the InteropServices.Automation object… some

using System.Runtime.InteropServices.Automation;

This is important, because I need to first evaluate if in fact I can run this interop stuff. Remember, I am assuming that the application is running as a desktop application, and not a web application. So I update the ShowCalculator_CanExecute method with the following  incredibly time consuming code and complicated code…

partial void ShowCalculator_CanExecute(ref bool result)
        {
            result = AutomationFactory.IsAvailable;
        }

The above will tell the screen that, if interop is available, show the button. If not, don’t show it.

Next I go back into the screen designer and just like I did with the CanExecute code, I select Edit Execute Code for the Show Calculator data item…

In the code window, I update the ShowCalculator_Execute method with the following…

partial void ShowCalculator_Execute()
        {
            MyCalculator.ShowCalculator();
        }

Here is the entire code behind for the screen…

(C#)

using System;
using System.Linq;
using System.IO;
using System.IO.IsolatedStorage;
using System.Collections.Generic;
using Microsoft.LightSwitch;
using Microsoft.LightSwitch.Framework.Client;
using Microsoft.LightSwitch.Presentation;
using Microsoft.LightSwitch.Presentation.Extensions;
using System.Runtime.InteropServices.Automation;

namespace LightSwitchApplication
{
    public partial class CreateNew
    {
        partial void ShowCalculator_CanExecute(ref bool result)
        {
            result = AutomationFactory.IsAvailable;
        }

        partial void ShowCalculator_Execute()
        {
            MyCalculator.ShowCalculator();
        }

    }
}

(VB.Net)

Imports System.Linq
Imports System.IO
Imports System.IO.IsolatedStorage
Imports System.Collections.Generic
Imports Microsoft.LightSwitch
Imports Microsoft.LightSwitch.Framework.Client
Imports Microsoft.LightSwitch.Presentation
Imports Microsoft.LightSwitch.Presentation.Extensions
Imports System.Runtime.InteropServices.Automation

Namespace LightSwitchApplication
	Public Partial Class CreateNew
		Private Partial Sub ShowCalculator_CanExecute(ByRef result As Boolean)
			result = AutomationFactory.IsAvailable
		End Sub

		Private Partial Sub ShowCalculator_Execute()
			MyCalculator.ShowCalculator()
		End Sub

	End Class
End Namespace

Now all that is left to do is run it and see what happens…

SCORE!!

That was easy. Now, if wanted to make it real interesting, I would add some nifty logic to Singleton the calculator, or maybe even do some User32.dll calls to handle some callbacks and get the value of the calculator for a field. That would be awesome… let me know when you do it  so I can copy what you did, okay?

Cheers!