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Reading/Writing cookies with HtmlPlaceholder for Silverlight

by Kiril Stanoev
May 10, 2011 Web 0 Comments


Recently we received a support ticket with a question whether RadHtmlPlaceholder provides support for cookies. By default, RadHtmlPlaceholder doesn't have a mechanism for reading/writing cookies. However, with the right bits of JavaScript, everything is possible :)
Imagine you have an HTML page which you want to read/write cookies to and all this has to happen from Silverlight.

First, you need few JavaScript methods for reading/writing cookies. Let's call the page we want to read/write cookies to CookiesPage.html.

<html>
    <head>
        <title>Cookies Page</title>
        <script type="text/javascript">
            // Create a cookie with the specified name and value
            function SetCookie(name, value) {
                document.cookie = name + "=" + value;
                alert("Cookie successfully set");
            }
            // Retrieve the value of the cookie with the specified name
            function GetCookie(cookieName) {
                // cookies are separated by semicolons
                var allCookies = document.cookie.split("; ");
                for (var i = 0; i < allCookies.length; i++) {
                    // a name/value pair (a crumb) is separated by an equal sign
                    var currentCookieName = allCookies[i].split("=");
                    if (cookieName == currentCookieName[0])
                        return allCookies[i];
                }
                // a cookie with the requested name does not exist
                return null;
            }
            // Retrieve all cookies
            function GetAllCookies() {
                var allCookies = document.cookie.split("; ");
                return allCookies;
            }
        </script>
    </head>
    <body bgcolor="aqua">
        <h1>Cookies page</h1>
    </body>

</html>

Next, the Silverlight part. On the page, you need several TextBox controls for reading/writing cookies and a RadHtmlPlaceholder for displaying the HTML page that contains the cookies.



The code-behind approach is pretty simple. Execute the JavaScript methods using RadHtmlPlaceholder's IFrame.

public MainPage()
{
    InitializeComponent();
 
    // Get the IFrame from the HtmlPresenter
    HtmlElement iframe = (HtmlElement)htmlPlaceholder1.HtmlPresenter.Children[0];
    // Set an ID to the IFrame so that can be used later when calling the javascript
    iframe.SetAttribute("id", "myIFrame");
}
 
// Writes a cookie
private void SetCookie()
{
    // Define a name for the cookie
    var name = this.txtSetCookieName.Text;
     
    // Define a value for the cookie
    var value = this.txtSetCookieValue.Text;
     
    // Call the SetCookie(name,value) JavaScript method
    string code = string.Format("document.getElementById('myIFrame').contentWindow.SetCookie('{0}','{1}')", name, value);
    HtmlPage.Window.Eval(code);
}
 
// Gets a cookie
private void GetCookie()
{
    // Get the name of the cookie we're looking for
    string name = this.txtGetCookieName.Text;
     
    // Call the GetCookie(name) JavaScript method
    string code = string.Format("document.getElementById('myIFrame').contentWindow.GetCookie('{0}')", name);
    var result = HtmlPage.Window.Eval(code);
     
    // Get the value of the cookie and display it
    var value = result.ToString().Split('=')[1];
    MessageBox.Show("Value: " + value);
}
 
// Gets all cookies
private void GetAllCookies()
{
    // Call the GetAllCookies JavaScript method to retrieve all cookies
    string code = "document.getElementById('myIFrame').contentWindow.GetAllCookies()";
     
    // Display the result in a ListBox
    ScriptObject result = HtmlPage.Window.Eval(code) as ScriptObject;
    int i = 0;
    this.cookies.Clear();
    while (result.GetProperty(i) != null)
    {
        this.cookies.Add(result.GetProperty(i) as string);
        i++;
    }
}

That's it. You can take a look at the video which demonstrates the application or you can download the sample project bellow.

CookiesSupport.zip

RadControls for Silverlight

Telerik UI for Silverlight, XAML
About the Author

Kiril Stanoev

Hi, I'm Kiril and I'm the Product Manager of Telerik UI for Android, Windows Universal and Windows Phone. Feel free to ping me on +KirilStanoev or @KirilStanoev

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