Wyatt Says...

One of the great things about Vista and Windows 7 is the user isolation. Even admin users need to “elevate” their account to make system changes. Take this Date and Time dialog from Windows 7 as an example:

Every user can view the Date and time, but only administrators can change it.

Adding this ability to your .NET application

Although this series of articles is called “7 days of Windows 7” this particular article is applicable to Windows 2000 – Windows 7.

Step 1. Do we have permission?

The first step is to check if we can write to system registry or system files & folders. There are many ways to do this, but the easiest method is a simple Windows API call:

// check if user is an admin for Windows 2000 and above
[DllImport("shell32.dll", EntryPoint = "#680", CharSet = CharSet.Unicode)]
public static extern bool IsUserAnAdmin();

This will return false if you’re a limited user on Windows 2000 – Windows 7, and will also return false if you are an admin but aren’t elevated on Windows Vista and Windows 7.

In other words, it will return false if you don’t have permission to access system files & registry. And ‘ IsUserAnAdmin” returns true if you do have permission.

Step 2. Notifying the user that elevation will happen: UAC Shield Icon

To set the shield icon to one of your buttons you have to do a few things. First, set the FlatStyle of your button to “System”:

Next, you need to define a couple of functions:

public static bool AtLeastVista()
{
    return (Environment.OSVersion.Platform == PlatformID.Win32NT && Environment.OSVersion.Version.Major >= 6);
}

[DllImport("user32.dll", CharSet = CharSet.Unicode)]
public static extern IntPtr SendMessage(HandleRef hWnd, UInt32 Msg, IntPtr wParam, IntPtr lParam);

public static void SetButtonShield(Button btn, bool showShield)
{
    //Note: make sure the button FlatStyle = FlatStyle.System
    // BCM_SETSHIELD = 0x0000160C
    SendMessage(new HandleRef(btn, btn.Handle), 0x160C, IntPtr.Zero, showShield ? new IntPtr(1) : IntPtr.Zero);
}

Now, simply use this snippet in your code:

…
// UAC Shield on next button for Windows Vista+
if (AtLeastVista())
    SetButtonShield(btnName, true);
…

Step 3. Re-launching process with administrator privileges

All we have to do now is show the elevation dialog and elevate the current program. You might want to specify some arguments, but the barebones of it is as follows:

ProcessStartInfo psi = new ProcessStartInfo
                           {
                               Arguments = "-justelevated",
                               ErrorDialog = true,

                               // Handle is the handle for your form
                               ErrorDialogParentHandle = Handle,
                               FileName = Application.ExecutablePath,
                               Verb = "runas"
                           };
try
{
    Process.Start(psi);
    Close();
}
catch (Exception ex)
{
    // the process couldn't be started. This happens for 1 of 3 reasons:

    // 1. The user cancelled the UAC box
    // 2. The limited user tried to elevate to an Admin that has a blank password
    // 3. The limited user tries to elevate as a Guest account
    MessageBox.Show(ex.Message);
}

Step 4. Code signing

Chances are that if you try to elevate your application you’ll get an ugly yellow elevation box:

To get the nice UAC box you’ll need to code sign your application. I won’t link to any code signing providers (because the list is huge), but you can get a code signing certificate from anywhere between $100 for 3 years to $400 or $500 for a single year. It depends on the company you use and the amount of searching you want to do.

7 Days of Windows 7

Join me tomorrow when I talk about Every possible Windows Vista and Windows 7 .NET Control You could ever want. See the full list of articles in the series.

In today’s tip I’m going to cover showing drag & drop icons. Specifically keeping the icon overlay shown when you drag files from Windows Explorer to your .NET application. Here’s a close-up of a user dragging files from a folder into wyBuild.

If we had used the normal .NET Framework interfaces for dragging files to wyBuild as soon as the cursor passes into the window the icons would disappear.

But, as you can see in the screenshot, the icons stay when dragging over our window. We can also set the drag & drop text to the current folder the user is dragging over.

How to add this to your app

This is one control I can’t take credit for. Adam Root from Microsoft wrote up a nice control on his blog in a post Shell Style Drag and Drop in .NET – Part 3. The control works for both Windows Form and Windows Presentation Foundation (WPF) applications.

He wrote a 3 part series, and it’s interesting if you want to dig into the nitty-gritty Windows API.

How we use Drag & Drop in wyBuild

We use the Windows Form control in wyBuild, but we have to use a little trickery to get it work right. Because Adam wrote the Drag & Drop control using a .NET Framework 3.5 language feature, and wyBuild is built using .NET Framework 2.0, we have to use this little trick from Daniel Moth.

Just add this snippet of code to your project and you’ll be all set to go.

//HACK: this is to support a .NET language 3.5 feature in .NET 2.0
//see, http://www.danielmoth.com/Blog/2007/05/using-extension-methods-in-fx-20.html
namespace System.Runtime.CompilerServices
{
    public class ExtensionAttribute : Attribute { }
}

7 Days of Windows 7

Join me tomorrow when I talk about Using shield icons, UAC, and process elevation. See the full list of articles in the series.

This will be another easy tip because all the work is already done and wrapped up in a nice little control. It’s open source and handles all of the details, get it here.

Progress bars in Windows 7 are nearly identical to what they were in Windows Vista. They’re green, animated and have 3 states: Normal, Error, and Paused:

Using Windows API

To get both the 3-state progress bar (regular, error, and paused) along with the taskbar progress bar we need to use some Windows API. The easier of the two to implement is changing the state of the progress bar. This works on Windows Vista and Windows 7:

[DllImport("user32.dll", CharSet = CharSet.Auto)]
internal static extern int SendMessage(IntPtr hWnd, int wMsg, int wParam, int lParam);

SetPaused()
{
    // 0x410 = PBM_SETSTATE
    // 0x0003 = PBST_PAUSE
    SendMessage(progressBar.Handle, 0x410, 0x0003, 0);
}

SetError()
{
    // 0x0002 = PBST_ERROR
    SendMessage(progressBar.Handle, 0x410, 0x0002, 0);
}

SetNormal()
{
    // 0x0001 = PBST_NORMAL
    SendMessage(progressBar.Handle, 0x410, 0x0001, 0);
}

Then there’s the matter of the taskbar progress bar in Windows 7. You can download the Windows7ProgressBar source code (zip file) to see how I did it, but the gist of it is you need to implement the ITakbarList3 Interface, and then use the SetProgressState to set the state (Normal, Error, Paused, or Marquee) and SetProgressValue to set the value.

7 Days of Windows 7

Join me Monday when I talk about Drag & Drop icons. See the full list of articles in the series.