today I want to share an implementation I’m using in my personal prototyping-Framework for Silverlight. This is important to mention, because I have tested it only for “works” but not including any productive parameters like memory-usage or processing-time.

The meaning of a prototyping-framework for me is to get thinks working as quick as possible, to show the outcome to my customer. There are some things I need very often, and so I’m using base-classes a lot.

One of them is ModelBase. Every time I need a Model kind of class, I let it inherit from ModelBase and even my ViewModelBase is inheriting from it.

This base-class is implementing INotifyPropertyChanged and offers me ways to deal with this kind of properties. A typical implementation of a property within a model would look like this:

 	[IsNotifyingProperty(NotifyAlsoFor = "FullName"]
        public string FirstName
        {
            get
            {
                return GetProperty<string>(this);
            }
            set
            {
                SetProperty(this, value);
            }
        }

You recognize two things. First the Attribute called IsNotifyingProperty and the other one are the two access-methods just taking the current object and in case of SetProperty the value to set. You see, its very easy to copy-and-paste if needed, and no further changes are necessary when the name changes (Except the binding somewhere).

The Implementation of the attribute looks like this:

namespace BaumannSolutions.Common.Attributes
{
    public class IsNotifyingProperty : Attribute
    {
        public string NotifyAlsoFor { get; set; }
    }
}

You see, there is one property in it, we will get to this later. A property itself isn’t enough to do what is planned, so there is some code in the constructor of ModelBase that looks like this:

var props = this.GetType().GetProperties();
 
            foreach (PropertyInfo pi in props)
            {
                var attr = pi.GetCustomAttributes(true);
                foreach (object o in attr)
                {
                    if (o is IsNotifyingProperty && !NotificationProperties.ContainsKey(pi.Name))
                    {
                        Type proptype = pi.PropertyType.GetType();
                        NotificationProperties.Add(pi.Name, ModelBase.GetDefault(proptype));
 
                        if (((IsNotificationChanged)o).NotifyAlsoFor != null)
                        {
                            NotificationAlsoProperties.Add(pi.Name, ((IsNotificationChanged) o).NotifyAlsoFor);
                        }
                    }
                }
            }

and these class wide collections:

protected Dictionary<string, object> NotificationProperties = new Dictionary<string, object>();
protected Dictionary<string,object> NotificationAlsoProperties = new Dictionary<string,object>();

As you see in the code, reflection is used to check for the properties and there attributes, and if IsNotificationProperty is found, the Property will be added to the collection NotificationProperties and there will be stored a default-value via a helper method. I wont publish it here, it should be very obvious what the method is doing.

You have also the chance to give a property, for which there should also be a PropertyChanged event in case the current Property is changed. I hope I’ve chosen a good example by using FirstName and FullName. If the FirstName is changed, you may want to raise PropertyChanged also for the FullName, cause FirstName is a subset of it.

the last parts we need are the two methods GetProperty and SetProperty. They look like this:

 
  protected V GetProperty<V>(DependencyObject parent)
        {
             var name = GetPreviousMethodName(MethodBase.GetCurrentMethod()).Replace("get_", "");
             if (NotificationProperties.ContainsKey(name))
             {
                 try
                 {
                     var ret = NotificationProperties[name];
                     if (ret != null)
                         return (V) ret;
 
                     return default(V);
                 }
                 catch (Exception)
                 {
                     return (V)GetDefault(typeof(V));
                 }
 
             }
            return default(V);
        }
 
 
 protected void SetProperty(DependencyObject parent, object value)
        {
            var name = GetPreviousMethodName(MethodBase.GetCurrentMethod()).Replace("set_", "");
            if (NotificationProperties.ContainsKey(name))
            {
                NotificationProperties[name] = value;
                RaisePropertyChanged(name);
            }
 
            if (NotificationAlsoProperties.ContainsKey(name))
            {
                    RaisePropertyChanged(NotificationAlsoProperties[name]);
            }
        }
 
 
  private string GetPreviousMethodName(MethodBase currentMethod)
        {
            string methodName = String.Empty;
 
            try
            {
                StackTrace sTrace = new StackTrace();
 
                for (Int32 frameCount = 0; frameCount < sTrace.FrameCount; frameCount++)
                {
                    StackFrame sFrame = sTrace.GetFrame(frameCount);
                    MethodBase thisMethod = sFrame.GetMethod();
 
                    if (thisMethod == currentMethod)
                    {
                        if (frameCount + 1 <= sTrace.FrameCount)
                        {
                            StackFrame prevFrame = sTrace.GetFrame(frameCount + 1);
                            MethodBase prevMethod = prevFrame.GetMethod();
                            methodName = prevMethod.Name;
                        }
                        break;
                    }
                }
            }
            catch (Exception ex)
            {
            }
 
            return methodName;
        }

So, you read carefully and have recognized a third method I haven’t mentioned yet Its just a helper-method to get the name if the calling Method. In our cases it will be set_Firstname and get_Firstname, the getter and setter of the property. That’s why you just have to pass this and don’t need to give the property name as a parameter. Just to make it even more simple to use and copy-and-paste the code.

The GetProperty generic method returns the typed property-value from the inner-collection and the SetProperty sets the value within this collection. It also raises PropertyChanged for the value and if defined the PropertyChanged for a related value.

Hope that gives you some inspiration to implement your own little framework to make live easier. I have a similar implementation for DependencyProperties and I will write about that soon.

Cya

Sascha

I originally planed to write a blog-post about the right way to localize Silverlight Apps. While researching I came across two really good posts about that topic already. So instead of writing the same stuff again, I follow an extended D.R.Y.-Principal ( I might call it D.R.O.P – Don’t repeat other people ) and point you in the right direction instead

A short but clear post about Localization was written by Patric Schouler on dotnet-redzone.blogspot.com.

If you like more detail and "Hands-On"-Experience have a look at the Post "Localizing Business Application" by Brad Adams.

Keep on improving !

Sascha

just found a nice Silverlight game for Phone 7. You can play it in the browser, don’t need a phone or emulator.
Check out DroppyPop

Cheers
Sascha

For example, if I want to apply the factory-pattern to my ViewModels and want every Model to have a static Create-Method I can simply implement this Method in the Base-Class.

public class ViewModelBase 
{ 
	public virtual ViewModelBase Create() 
	{ 
		return new ViewModelBase(); 
	} 
}

Of cause, without Generics we are limited to the return-Type. We could now override this method in every specific ViewModel to at least return the right ancestor of ViewModelBase. An easier way is, to use Generics for this case. The class could look like this :

public class ViewModelBase<TViewModel> where TViewModel : ViewModelBase 
{ 
	public virtual TViewModel Create() 
	{ 
		return Activator.CreateInstance(typeof(TViewModel)); 
	} 
}

Now we can simply create our new specific ViewModel like this

public class MyViewModel : ViewModelBase<MyViewModel>

to get what we want generically.

Another possible scenario would be the following. We know, every ViewModel contains a Collection of Models, all inheriting from a class called ModelBase. we could extend out code the following way:

public class ViewModelBase<TViewModel> where TViewModel : ViewModelBase 
{ 
	public virtual TViewModel Create() 
	{ 
		return Activator.CreateInstance(typeof(TViewModel)); 
	} 
 
	public List<ModelBase> MyList {get;set;} 
}

or, the better way, we could extend our Generic header to be type safe.

public class ViewModelBase<TViewModel, TChildModel> 	
                                        where TViewModel : ViewModelBase 
					where TChildModel : ModelBase 
{ 
	public virtual TViewModel Create() 
	{ 
		return Activator.CreateInstance(typeof(TViewModel)); 
	} 
 
	public List<TChildModel> MyList {get;set;} 
}

Defining a Class by

public class MyViewModel : ViewModelBase<MyViewModel, MyModel>

Like always, if we talk about inheritance, you should avoid to go too far with that. I implemented a Framework I use for rapid prototyping where a lot of things are done in the base-class via reflection, but in a productive environment its not always what you want. Plan your development as precise as possible.

• What do you want to be individually implemented by each ViewModel ?
• When is it a good thing to implement it in the Base-Class ?
• How confusing is you inheritance for other developers ?

Good Luck

It took me a while to figure it out. My Solution is based on Firefox Portable and these are the steps to do:

1. First uninstall your Silverlight 3 Runtime to be able to install Sl 4

2. Then Install SL 4 Runtime. You can download it from Microsofts getStarted Page

3. Copy the Files C:\Program Files\Microsoft Silverlight\4.xxxxx to a temporary Folder

4. Uninstall Silverlight 4 and reinstall Silverlight 3. If you don’t have the Runtime at hand, you can download it Here. (I could not find the actual Download-Page or a Runtime-Archive. You can help me out here ?

5. Copy the temporary saved files to your Firefox Portable Folder under \Data\plugins

Done that, the IE (and the Rest of the System) uses the installed SL 3 Runtime, while your Firefox Portable uses the SL 4 you copied to the Plug-in Folder.

The only downside is, that the Silverlight-Info within the Browser will show Version 3, cause that’s the officially  installed one on the System.

Anyway, I did a few tests, and everything seems to work fine. Let me know about your experience with this.

Guess what, I found an article from Andy Beaulieu doing exactly that:

" Improved HitTest Method for Silverlight 3" from Andy Beaulieu

one of my expectations as a Software Developer in 2010 is, that the WCF RIA Services for Silverlight will become a huge  thing. So I did some research, and found a nice webcast by Ronnie Sauermann from Microsoft Switzerland. I met him during a project I did last summer, and he has a very good way to explain things. check it out! I unfortunately found no way to directly bookmark the video. So click the link and navigate down to Ronnies Video about RIA Services.

Video from Shapes ‘09 about WCF RIA Services

The Features of this Version are:

• Silverlight 2.0 support
• C# code editor with syntax colorization, keywords and template code completion assist
• Automatic Build & Run
• Configurable Web application launch facilities
• Silverlight Project System and Silverlight Compiler: both an advanced project system for creating Silverlight applications and media experiences.
• XAML Editor & Preview: advanced, standards-compliant XAML editor with code hinting and code completion features which helps detect and correct coding errors.
• Move and Rename refactoring
• Advanced Media Features
• Cross Platform Capabilities (Mac version)
• Complete user documentation & Prescriptive Tutorials
• Defects & Regression Testing
• Developer Usability Testing

Version 2.0 is planned for Spring 2010. This is the roadmap:

• Silverlight 3.0 support
• Completion of re-organization Silverlight development environment
• Completion of the Extensibility, Support for Multiple Projects
• Improvements to Mac Platform
• Completion of Silverlight 3.0 Runtime Support "out of browser"

More Information can be found on the projects website www.eclipse4sl.org

If you are a Mac-User, there is also a plug-in for you. Check out the Microsoft Interop Website for Eclipse4SL.

I wish all of you a relaxing and successful 2010. See you on the other side )

Sascha

With Internet Explorer 8 Microsoft introduced a new feature called Webslices. Little pieces of information within your browser-bar (most commonly) about site-updates.

Now I tried to put a Silverlight app into a Webslice.

Herefor I created a new Silverlight App with a testpage like this (created automatically)

<form id="form1" style="height: 100%;">
<div id="silverlightControlHost">
<object width="100%" height="100%" type="application/x-shockwave-flash">
<param name="source" value="ClientBin/SilverlightWebslice.xap" />
<param name="onError" value="onSilverlightError" /><param name="background" value="white" />
<param name="minRuntimeVersion" value="3.0.40624.0" />
<param name="autoUpgrade" value="true" />
</object></div></form>

In my Silverlight-App I placed a Textblock saying “Welcome to my Silverlight Webslice”.

<Grid x:Name="LayoutRoot">
        <TextBlock Text="Welcome to my Silverlight Webslice"></TextBlock>
  </Grid>

And then, in default.aspx I put the Webslices-Code

<form id="form1">
<div id="SliceID" class="hslice" style="display: none">
<span class="entry-title">Silverlight Slice
<a style="display: none" rel="entry-content" href="SilverlightWebsliceTestPage.html">Alternative</a>
</div></form>

and voila, a silverlight Webslice.

Have fun playing arund with it )

Before I forget, there is an alternative for Firefox Browser called WebChunks. Unfortunately it doesn’t work for the current Version at the moment, hope the developer will keep on working on it.

Sascha