How many people have experienced the modal pop up in desktop applications? They are commonly used across a wide variety of applications, one could say, too commonly used. While not appropriate for all situations, sometimes you need to use a pop up.

In XBAP applications the ability to open a pop-up is very limited; in many cases you will use navigation and multiple pages instead of separate windows. In most cases this is sufficient, but sometimes you really need to use a pop-up, and when you do a simple work around is to use the Popup control offered by WPF.

First, you define the Popup in the markup, making sure to set its StaysOpen property to true so it will remain open until you close it. (There’s no point in using the PopupAnimation or AllowsTransparency properties, because they won’t have any effect in a web page.) Include suitable buttons, such as OK and Cancel, and set the Placement property to Center so the popup will appear in the middle of the browser window.

Code sample:

<Popup Name="dialogPopUp" StaysOpen="True" Placement="Center" MaxWidth="200">

    <Border>

        <Border.Background>

            <LinearGradientBrush>

                <GradientStop Color="AliceBlue" Offset="1"></GradientStop>

                <GradientStop Color="LightBlue" Offset="0"></GradientStop>

            </LinearGradientBrush>

        </Border.Background>

        <StackPanel Margin="5" Background="White">

            <TextBlock Margin="10" TextWrapping="Wrap">Please enter your name.

            </TextBlock>

            <TextBox Name="txtName" Margin="10"></TextBox>

            <StackPanel Orientation="Horizontal" Margin="10">

                <Button Click="dialog_boxOK_Click" Padding="3" Margin="0,0,5,0">OK</Button>

                <Button Click="dialog_boxCancel_Click" Padding="3">Cancel</Button>

            </StackPanel>

        </StackPanel>

    </Border>

</Popup>

At the appropriate time (for example, when a button is clicked), disable the rest of your user interface and show the Popup. To disable your user interface, you can set the IsEnabled property of some top-level container, such as a StackPanel or a Grid, to false. (You can also set the Background property of the page to gray, which will draw the user’s attention to Popup.) To show the Popup, simply set its IsVisible property to true.

Here’s an event handler that shows the previously defined Popup:

private void popupTriggerButton_Click(object sender, RoutedEventArgs e)

{

    DisableMainPage();

}

private void DisableMainPage()

{

    mainPage.IsEnabled = false;

    this.Background = Brushes.LightGray;

    dialogPopUp.IsOpen = true;

}

When the user clicks the OK or Cancel button, close the Popup by setting its IsVisible property to false, and re-enable the rest of the user interface:

private void dialog_boxOK_Click(object sender, RoutedEventArgs e)

{

    // Copy name from the Popup into the main page.

    lblName.Content = "You entered: " + txtName.Text;

    EnableMainPage();

} 

private void dialog_boxCancel_Click(object sender, RoutedEventArgs e)

{

    EnableMainPage();

}

private void EnableMainPage()

{

    mainPage.IsEnabled = true;

    this.Background = null;

    dialogPopUp.IsOpen = false;

}

Using the Popup control to create this workaround has one significant limitation. To ensure that the Popup control can’t be used to spoof legitimate system dialog boxes, the Popup window is constrained to the size of the browser window. If you have a large Popup window and a small browser window, this could chop off some of your content. One solution is to wrap the full content of the Popup control in a ScrollViewer with the VerticalScrollBarVisibility property set to Auto.

If a Popup isn’t suitable for you, you can try another more “interesting” approach for showing a dialog box. Using the Windows Form library from .NET 2.0 you can safely create and host any WinForm control in your WPF application. In this case, you can create and show an instance of the System.Windows.Forms.Form class (or any custom form that derives from Form), because it doesn’t require unmanaged code permission. In fact, you can even show the form modelessly, so the page remains responsive. The only drawback is that a security balloon automatically appears superimposed over the form and remains until the user clicks the warning message. You’re also limited in what you can show in the form. Windows Forms controls are acceptable, but WPF content isn’t allowed.

Labels: .NET, c#, code sample, popup, WPF, XBAP

# posted by Romeo Dumitrescu @ 10:36 p.m. 71 comments

In some design scenarios launching multiple copies of the same WPF application is a problem, especially for document-based applications or server applications.

WPF does not provide a native solution for single instance applications; however there are several workarounds for this issue.

The most commonly used solution is to check whether another instance of the application is already running when the Application.Startup event fires. This is easily done using a system wide mutex (provided by the operating system to allow interprocess communication). While this is easily done, it limits the developer’s options by not providing a way for the new instance to communicate with the already running instance. Mainly this will provide only a simple way of limiting the number of running instances to one, while a separate system will be required to handle the new calls (usually through remoting or Windows Communication Foundation).

The recommended and more useful approach is to use the built-in support that’s provided in Windows Forms and originally intended for Visual Basic applications. This approach handles the messy plumbing behind the scenes. This means using an old style application class as wrapper for the WPF application. The wrapper will handle the instance management and will communicate the request to the already running instance of the WPF application.

Solution steps:

1) Add a reference to the Microsoft.VisualBasic.dll assembly.

2) Add a new custom class derived from the Microsoft.VisualBasic.ApplicationServices.WindowsFormsApplicationBase class.

3) The IsSingleInstance must be set to true in the constructor. This enables a single instance application.

4) Override the OnStartup() method to create the WPF application object. (Note: The OnStartup() method is triggered when the application starts)

5) Overide the OnStartupNextInstance() method to handle future instances. (Note: The OnStartupNextInstance() method is triggered in when another instance of the application starts up)

6) Define a Main entry point for the application and create the wrapper object

7) Create the WPF application class

Sample of the application wrapper: 

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using Microsoft.VisualBasic.ApplicationServices;

using System.Windows;

namespace SingleInstanceApplication

{

    //The Main entry point class

    public class Startup

    {

        [STAThread]

        public static void Main(string[] args)

        {

            SingleInstanceAppWrapper wrapper = new SingleInstanceAppWrapper();

            wrapper.Run(args);

        }

    }

    //The old-style application wrapper

    public class SingleInstanceAppWrapper : WindowsFormsApplicationBase

    {

        public SingleInstanceAppWrapper()

        {

            // Enable single-instance mode.

            this.IsSingleInstance = true;

        }

        // Create the WPF application class.

        private WPFApplication _app;

        //Override OnStartup() method to create the WPF application object

        protected override bool OnStartup(

             Microsoft.VisualBasic.ApplicationServices.StartupEventArgs e)

        {

            _app = new WPFApplication();

            _app.Run();

            return false;

        }

        // Override OnStartupNextInstance() to handle multiple application instances.

        protected override void OnStartupNextInstance(

             Microsoft.VisualBasic.ApplicationServices.StartupNextInstanceEventArgs e)

        {

            //In case of command line arguments, send them to the WPF application object    

            if (e.CommandLine.Count > 0)

            {

                _app.HandleCommandLine(e.CommandLine);

            }

        }

    }

}

As you can see, the sample above contains the Main entry point for the application. This is required because the wrapper must be created first.
If Visual Studio is used, by default the App.xaml application definition style is used. This will not work with the wrapper because the App.xaml approach already has a Main entry point.
Remove App.xaml and App.xaml.cs from the project and create a new class for the entry point.

The only thing left to do is to create the WPF application definition:

public class WPFApplication : System.Windows.Application

{

    //Override the OnStartup() method

    protected override void OnStartup(System.Windows.StartupEventArgs e)

    {

        base.OnStartup(e);

        //Load the main window

        Window _MainWindow = new Window();

        _MainWindow.Show();

        //Set the MainWindow property for the WPF application object

        this.MainWindow = _MainWindow;

    }

    //Method used to handle command line arguments

    public void HandleCommandLine (System.Collections.ObjectModel.ReadOnlyCollection<string> e)

    {

        //Code to handle command line arguments from other instances goes here

    }

}

Because the wrapper approach does not contain a XAML application definition (App.xaml), if you need to load application level resources, the following code can be placed the OnStartup() of the WPF application definition to load the resources from a resource dictionary:

        Application.Current.Resources.MergedDictionaries.Add(

            Application.LoadComponent(

                new Uri("AssemblyName;component/ApplicationResourceDictionary.xaml",

                UriKind.Relative)) as ResourceDictionary);

The above code will work for dynamic resource definitions. The static resource lookup process will fail because the source for the application resources dictionary need to be specified. In that case the code to load the resources will be replaced with the following:

Application.Current.Resources.Source = 

    new Uri("/AssemblyName;component/ApplicationResourceDictionary.xaml", UriKind.Relative);

Note: AssemblyName is a placeholder for the actual assembly name. The Uri for the resource dictionary location can be changed as required.

Labels: .NET, c#, embedded, Visual Basic, Win32, WPF

# posted by Romeo Dumitrescu @ 11:49 a.m. 41 comments

As we have found out in part 1, SharePoint can manipulate data using the user profile management objects and can accept data from external sources. Using these two features apart we have two limited tools with limited usage, but using them together gives us a powerful, flexible and efficient method of storing and using data from any internal or external resource.

It’s time to see this solution to our problems in action.

Code example of getting/setting the profile property from a C# application

The concept is the same for any source of information (web services, web applications, etc.):
Get the user’s profile->Get the required profile property->Get/Set profile property value

Code example: (note that to access profile properties, this code must run with elevated privileges)

string value;
try
{
 SPSecurity.RunWithElevatedPrivileges(delegate()
 {
  
     // Change the site address for different deployment environments
     // Note: WIN2003STD is a place holder for your environment, usually your server name
     SPSite site = new SPSite("http://WIN2003STD/");
     SPWeb web = site.OpenWeb();

     // Get the profile manager object for the site
     UserProfileManager profileManager = new UserProfileManager(ServerContext.GetContext(site));

     // Use the username from the User Information Item to get the full profile of an user
     UserProfile user_profile = profileManager.GetUserProfile(System.Web.HttpContext.Current.User.Identity.Name);

     // Get the required profile property value from the profile
     value = user_profile["MyProperty"].Value.ToString();

  
 });
}
catch (Exception e)
{
 return "Error getting user info: " + e.Message.ToString();
}

user_profile["MyProperty"].Value gets or sets the profile property value.

This is a very convenient way of using profile properties to store required information for each user. Properties can be set as read-only or not to appear in the user’s profile, which gives you even more control.

Tools You Never Knew You Had… (and what to do with them now that you’ve wised up!)

External applications running on the server can access this information the same way, so a bridge between SharePoint and applications like web sites, game servers, messaging apps, etc. can be easily created.

SharePoint Complications, As Usual

Watch out that the profile property might be set as read-only in SharePoint. Even if it’s the case however, the above code should still be able to access the profile because it’s running with elevated privileges. So if there is a situation in which the user is allowed to see the data but only modify it by using a service (like a web application or web service), this is a good way of doing it.

So we now have a way to store data and manipulate it according to our needs. We can control it, we can validate it and most important of all, we decide how the user interacts with the data.

Labels: c#, code quality, SharePoint, string conversion, web development, Win32

# posted by Romeo Dumitrescu @ 9:28 a.m. 49 comments

Public void MyFunction(int TableA_ID, int TableB_ID, String someOtherValue);

int A_ID = 5;
int B_ID = 4;
MyFunction(B_ID, A_ID, "Hello World");

    public struct UserID
 {
     private int value;
     public static implicit operator int(UserID source)
     { return source.value; }

     public UserID(int intValue)
     {
         value = intValue;
     }
  }

 private void TryToFail(UserID test) { } 

 UserId works = new UserId(5);
 int fails = works;

 TryToFail(works) //compiles fine
 TryToFail(fails) //Doesn't compile

Labels: c#, semantic

# posted by Jake @ 2:43 p.m. 17 comments