Silverlight Tips provides simple and useful tutorials and tips with real life examples, live demos and sample codes to download.
About authors:
Damon Serji
Damon Serji,
Silverlight developer working at Metia in London.
Gavin Wignall
Gavin Wignall,
Interactive Design Lead, working in design for over 10 years, the last 3 being in Silverlight.
Allan Muller
Allan Muller,
Developer, working on various types of Silverlight and WCF projects.

To set the margin or Canvas of an object from the code you can use SetValue() which is a built-in method. SetValue() takes a DependencyProperty such as a Button, and a double value.

Example:

myButton.SetValue(Canvas.LeftProperty, myPoint.X);

In above example ‘myButton’ is a Button on the xaml, and myPoint is a variable of type Point which we use the X value of.

Posted by Damon Serji on 11. January 2010 18:36 under: Basic
 with 0 Comments
Get Microsoft Silverlight

The built-in validation in Silverlight 3.0 is a great new feature that can be used on essential Silverlight controls such as TextBox. Using this feature, it is possible to nicely display an error message and highlight the TextBox that has bad value.

In this post I will only cover validating data in TextBox controls, which are simply used in most forms to receive basic information such as Name, Surname and Email address. The completed and working version of this project can be downloaded from CodePlex from here. I will explain and provide solution on how to validate ComboBox, Radio Button controls or etc in another post soon, so please keep yourself updated on new posts here.

1. Create a basic form with a few TextBox controls in the xaml

2. Create a class, call it CustomValidation
Add the following code to your CustomValidation class:

private string message;
public CustomValidation(string message)
{
    this.message = message;
}
public bool ShowErrorMessage
{
    get;
    set;
}
public object ValidationError
{
    get
    {
        return null;
    }
    set
    {
        if (ShowErrorMessage)
        {
            throw new ValidationException(message);
        }
    }
}

3. Create an Extension class (Extensions)
To understand what is an Extension class and for more information about them visit my tutorial post “Extension methods in Silverlight and C#”.

In brief: Extensions will be your Extension class to extend any object of type FrameworkElement like TextBox controls within your application framework. It means you can use the public methods within this class as a “built-in” method for your TextBox.

Create a static public method and call it SetValidation. This method receives an instance of a FrameWorkElement and a string value, and returns nothing:

public static void SetValidation(this FrameworkElement frameworkElement, string message)
{
    CustomValidation customValidation = new CustomValidation(message);
    Binding binding = new Binding("ValidationError")
    {
        Mode = System.Windows.Data.BindingMode.TwoWay,
        NotifyOnValidationError = true,
        ValidatesOnExceptions = true,
        Source = customValidation
    };
    frameworkElement.SetBinding(Control.TagProperty, binding);
}

CustomValidation is the class we defined earlier.

"Binding" is a class in System.Windows.Data assembly which gets or sets a value that indicates whether to raise the error attached event on the bound object.

What are we doing? Here we have a CustomValidation class that has one property ("ShowErrorMessage") and one public methods ("ValidationError"). "ValidationError" is our source binding object and what we want to be able to do in the future is to bind our frameworkElement, which is a TextBox, to ValidationError. We are in simple words binding the CustomValidation class to our TextBox once we call this method on our TextBox.

For more information on Binding and BindingExpression visi msdn article here.

Create another two methods for displaying validation error and also for clearing validation error when the error was corrected:

public static void RaiseValidationError(this FrameworkElement frameworkElement)
{
    BindingExpression b =
    frameworkElement.GetBindingExpression(Control.TagProperty);
    if (b != null)
    {
        ((CustomValidation)b.DataItem).ShowErrorMessage = true;
        b.UpdateSource();
    }
}

public static void ClearValidationError(this FrameworkElement frameworkElement)
{
    BindingExpression b =
    frameworkElement.GetBindingExpression(Control.TagProperty);
    if (b != null)
    {
        ((CustomValidation)b.DataItem).ShowErrorMessage = false;
        b.UpdateSource();
    }
}

By creating a new BindingExpression you will be creating an instance of your binding so you can control the properties and public methods of your binding source/target. In above case, we are casting the BindingExpression.DataItem as CustomValidation. This enables us to access the properties of this class, "ShowErrorMessage" in this case.

4. RaiseValidationError() and ClearValidationError()
So now we have our TextBox, a method in our Extension class to bind the TextBox to our CustomValidation class and passes our error message, and a method in our Extension class that fires throw new ValidationException(message); from the CustomValidation class.

All we need to do now is to check if a specific TextBox is valid or not. If the TextBox was not valid we can simply use the RaiseValidationError() and ClearValidationError() methods, which should now be available from the intellisense in Visual Studio, to throw the validation exception and display a suitable error message and we do that by following code when the submit button was pressed:

Name.ClearValidationError();
bool isFormValid = true;
if (Name.Text == "")
{
    Name.SetValidation("Please enter your name");
    Name.RaiseValidationError();
    isFormValid = false;
}

use isFormValid variable to check if you have to submit the form or not. The Name.ClearValidationError() makes sure you clear the form everytime you press submit, so if the form was valid the error message had already been cleaned.

I have some extra validation extensions on this project and have organised the code in different class files. Download the project from here.

Posted by Damon Serji on 8. October 2009 19:24 under: Advance, Intermediate
 with 9 Comments

This post is very much a combination of my three previous posts (Silverlight QueryString using TryParse() method, Validate GUID in Silverlight – Parse GUID in C# and Extension methods in Silverlight and C#) to demonstrate all these great features in one place. I have also added an Extension method in this project to validate Date and Time using a simple Regular Expression, for better validation I suggest change the Regular Expression to match your specific needs.

I am not explaining the code for this project as each part is explained in details in the posts I mentioned above, but please do feel free to ask any questions in the comment section below and I will try to answer as soon as I can.

This project can be downloaded from CodePlex from here, and feel free to play with the working version of it below.

Get Microsoft Silverlight
Posted by Damon Serji on 7. October 2009 18:57 under: Intermediate
 with 1 Comments

I have been looking around to find any built-in method to parse GUIDs in Silverlight, or to tell me if a value of type string is a valid GUID or not. After a few research I decided to create an Extension method to validate my GUID using Regular Expressions.

You can read more about Extension methods in Silverlight in my previous post here, but here I have a method to receive a string value and return true/false depending on if the sting value is a valid GUID or not. Anyway, here is what we can do to validate Silverlight GUID!

public static bool IsGUIDValid(string expression)
{
    if (expression != null)
    {
        Regex guidRegEx = new Regex(@"^(\{{0,1}([0-9a-fA-F]){8}-([0-9a-fA-F]){4}-([0-9a-fA-F]){4}-([0-9a-fA-F]){4}-([0-9a-fA-F]){12}\}{0,1})$");

        return guidRegEx.IsMatch(expression);
    }
    return false;
}

Posted by Damon Serji on 7. October 2009 16:17 under: Intermediate
 with 0 Comments

Extension methods are great way to add and use custom functionality on your objects.

So what is an Extension method?

In a short and simple describing: instead of creating a method that takes an instance of your object, applies your changes and then returns you the instance of that control, you can create an Extension method for that specific object to do the same thing but in a way of built-in within your object.

Example: if we had a TextBox that needed to have a valid text input:


<TextBox x:Name=”InputEmail/>

And you have:

string inputEmail = InputEmail.Text;

You can do:

If (inputEmail != “” && ValidateEmail(inputEmail) == true)
{
   .
   .
}
.
.
private bool ValidateEmail(string getInputEmail)
{
   .
   .
}

or you can do it in a much cleaner and easier to understand way using “IsEmailValid” extension, which extends the string:

if (inputEmail.IsEmailValid())
{

}

You can immediately notice from the above example that how much time and line of codes you will save by simply using Extensions instead of re-writing your custom methods to apply the same operation on a common object or element within a project that uses that feature in many places.

How to add an Extension method to Silverilght objects?

First we need to add a new static class that contains a static method for our new Extension method (IsEmailValid).

public static class FrameworkElementExtensionExtensions
{
    public static bool IsEmailValid (this string getInputEmail)
    {
        bool isMatched = true;
        Regex regex = new Regex(@"^[\w-\.]+@([\w-]+\.)+[\w-]{2,4}$");
        
        if (getInputEmail != “” && regex.IsMatch(s))
        {
            isMatched = false;
        }
        return regex.IsMatch(s);
    }
}

Note in the IsEmailValid method we used the keyword “this” before string getInputEmail, this simply means the IsEmailValid Extension method belongs to objects of type “string”.

To use the above extension method anywhere within your project, all you have to do is to import the reference to any of your classes, where you like the extension to be available, by adding “using FrameworkElementExtensionExtensions;” to that class.

Now you should even get the IsEmailValid method in your Visual Studio Intellisense when you add a dot after any string variable. So now you could simply do:

if (inputEmail.IsEmailValid()){
    HtmlPage.Window.Alert("Email was successfully submitted!");
}

Above example was a very simple example, I will update the example solution regularly to include more advanced examples for you to use (copy & paste!) in the future, so please check this post later for updates. Also, this example, along with more examples in the future, is available to download from CodePlex from here.

Posted by Damon Serji on 6. October 2009 09:37 under: Intermediate
 with 4 Comments

In order to get the value of your QueryString parameters from the URL all you need is this line of code:

int id = HtmlPage.Document.QueryString["ID"];

And you need to add Windows.Browser namespace for HtmlPage class:

using System.Windows.Browser;

However, there are always two situations which could break your application:

  1. if there are no “ID” parameters in the url
  2. if there is an “ID” parameter in the url, but it has a string value instead of an integer number.

To avoid breaking the code and causing runtime error we need to add a few conditions and also parse the value to integer instead of assigning it right away. We can use Int32.TryParse() method to test the value which we are about to assign to an integer variable before we actually do so, this way we will only assign it if it really is an integer:

int id = -1;
if (HtmlPage.Document.QueryString.ContainsKey("ID"))
{
    string queryStringValue = HtmlPage.Document.QueryString["ID"];
    if (Int32.TryParse(queryStringValue, out id))
    {
        // the result was successful and
        // the correct ID will be inserted to id
    }
    else
    {
        // the result was not successful                   
    }
}

Using above method, you ensure the id gets assigned a value only if the ID parameter in the url has a valid integer value, or it will remain as -1 if the value was not an integer.

Posted by Damon Serji on 30. September 2009 22:30 under: Basic, Intermediate
 with 3 Comments

In this example I will demonstrate how to use ImageBrush to fill area of shapes like rectangle or ellipse with an image.

In order to fill the area of a control like Rectangle control, we need to create an instance of type BitmapImage, and this is not possible if we do not have a Uri which points to a real image file.

So first, I create an Uri pointing to an image which I had put in the “images” folder in my Silverlight application project.

Hint: try to use Uri.TryCreate to create your Uri as by this way you stop your application from breaking if the path you gave your Uri was not valid or did not exist.

Second, create a new instance of BitmapImage and assign your Uri to its value.

Uri imageUri;
BitmapImage image = null;

if (Uri.TryCreate("images/SilverlightTips.jpg", UriKind.RelativeOrAbsolute, out imageUri))
{
    image = new BitmapImage(imageUri);
}

Now you can create a new instance of ImageBrush and assign your created BitmapImage to its ImageSource value:

ImageBrush imageBrush = new ImageBrush();
imageBrush.ImageSource = image;

Finally, using .Fill method on your Rectangle control fill the entire rectangle (or any other shapes your object is) with your ImageBrush. And here is how your final code should look like:

Uri imageUri;
BitmapImage image = null;

if (Uri.TryCreate("images/SilverlightTips.jpg", UriKind.RelativeOrAbsolute, out imageUri))
{
    image = new BitmapImage(imageUri);
}
if (image != null)
{
    ImageBrush imageBrush = new ImageBrush();
    imageBrush.ImageSource = image;
    Logo.Fill = imageBrush;
    LogoEllipse.Fill = imageBrush;
    LogoRectangle.Fill = imageBrush;
}

Download this project from CodePlex from here. Here it is working:

Posted by Damon Serji on 28. September 2009 13:42 under: Intermediate
 with 2 Comments
Get Microsoft Silverlight

Silverlight Child Window is a great new feature which enables you to use advantage of a fully enhanced popup window. Child Window can be customized just like a normal xaml file to display or request information from the user. In this post I will explain briefly how receive and save information entered by user from a Child Window (ChildWindowForm.xaml in our example) and then display them in the parent window (MainPage.xam).

I am going to create an example in which user enters his/her name and surname in a Child Window and once submitted different details, along with the entered name and surname, are displayed in the main page.

I have uploaded the working example of this post to CodePlex and you can download it from here to test it for yourself.

1. add a new Child Window
in Visual Studio = right click on your Silverlight project, then, Add > New Item > Silverlight Child Window. The Child Window will have an OK and a Cancel button by default when it is created. Add two TextBox controls to the page for users to enter their name and surname.

2. Create an EventHandler in Child Window
code to create a new EventHandler:

public event EventHandler SubmitClicked;

3. Create public properties to save the values
it is possible to access the value of the TextBox controls we added in the Child Window directly from the MainPage.xaml.cs, however, this is a terrible practice as it will reduces your code stability in the future. Therefore create two public properties of type string to save the value of both TextBox controls. You will notice in my project I save the value of the TextBox in a private string variable and then save that variable to my public – this is just a better practice for coding so don’t get confused.

public string NameText
{
    get { return _nameText; }
    set
    {
        _nameText = value;
    }
}
public string SurnameText
{
    get { return _surnameText; }
    set
    {
        _surnameText = value;
    }
}


4. Fire the event once submit button is clicked in Child Window
there should already be a method for when the OK (Submit) button is pressed, it is called OKButton_Click. Inside that we need to fire the event which we created earlier, so that our event gets fired when the code reaches this method i.e. when we press OK in Child Window.

private void OKButton_Click(object sender, RoutedEventArgs e)
{
    if (SubmitClicked != null)
    {
        _nameText = Name.Text;
        _surnameText = Surname.Text;
        SubmitClicked(this, new EventArgs());
    }
    this.DialogResult = true;
}


5. In MainPage.xaml create a new instance of the Child Window

in order to display your Child Window first create a private variable your Child Window type - what ever you called your Child Window file will be the type of your variable i.e. ChildWindowForm.xaml:

private ChildWindowForm childWindowForm;

now create a new instance of it:

childWindowForm = new ChildWindowForm();


6. How to show Child Window
you need to display the actual Child Window which you created and have the instance in your MainPage. To do that, use the instance you just created and call the build-in method for any Child Window called “Show”:

childWindowForm.Show();


7. In MainPage.xaml hook up the submit event in Child Window
now we have an event which will get fired up from the Child Window when we click the submit button (OK button). All we have to do is to wire that event up so that we can do something when it is fired:

childWindowForm.SubmitClicked += new
EventHandler(childWindowForm_SubmitClicked);


8. Access the properties of the Child Window

private void childWindowForm_SubmitClicked(object sender, EventArgs e)
{
    Name.Text = childWindowForm.NameText;
    Surname.Text = childWindowForm.SurnameText;
}



I have skipped explaining some features that you will see in the example I created for this project (download from here) to concentrate more on the subject of this post. However if you have any questions about this post or the example please do feel free to post your comments and I will try to help as much as I can.

Posted by Damon Serji on 24. September 2009 21:27 under: Intermediate
 with 8 Comments

You could use a variable globally in your .NET website if you declare it in your Web.config file.

in your Web.config file find <appSettings> tag and insert your variables before it's closing tag:

<appSettings>
  <add key="MyVariable1" value="False" />
  <add key="MyName" value="Damon Serji" />
</appSetting>

Now you can easily access this variable and its value from your C# code:

string myVariable = System.Configuration.ConfigurationSettings.AppSettings["MyName"];

To break the above code down and to make sense of it: System really looks in your Web.Config file and the rest of the line becomes more obvious when you look at your Web.Config structure:


<?xml version="1.0" encoding="UTF-8"?>
  <configuration xmlns="http://schemas.microsoft.com/.NetConfiguration/v2.0">
      <configSections>
      .
      .
      </configSections>     
      .
     <appSettings>
       <add key="MyVariable1" value="False" />
       <add key="MyName" value="Damon Serji" />
     </appSetting>
     .
     .

So your Web.Config is nothing but a simple XML. System.Configuration tells the compiler to look in to <configuration> tag and System.Configuration.ConfigurationSettings.AppSettings tells it specifically to look into the <appSettings> tag. The result is a simple array of other tags which were added by you manually, so to find a specific tag you need to give it the index of the array i.e. an integer, or the "key" for that array, which is another way to find the tag you are looking for.

Posted by Damon Serji on 22. September 2009 18:06 under: Intermediate
 with 1 Comments

meta tags contain useful information that could be used by user’s browser, search engine optimization, Java Script and etc. Some of the most common ones are "keyword" and "Description" meta tags which are used for better optimization.

Changing/Adding these meta tags is particularly useful if you display different data according to user’s setting or your application setting, e.g. if you have more than one language and want to have a different keyword meta tag for each language.

Here is how to add meta tags to your site programmatically:

HtmlMeta htmlMeta = new HtmlMeta();
htmlMeta.Name = "keywords";
htmlMeta.Content = "Tips, Silverlight Tips, SilverlightTips.com";
Page.Header.Controls.Add(htmlMeta);

Above code will generate the following code in your .aspx file:


<meta name="keywords" content="Tips, Silverlight Tips, SilverlightTips.com" />

Posted by Damon Serji on 22. September 2009 17:39 under: Intermediate
 with 0 Comments