How do I Pass a 'user' object from aspx to silverlight 4

Question

First, we are constrained to using an existing web framework that handles authentication and authorization. The web project uses forms authentication and writes to an encrypted cookie. The user information is exposed to the aspx pages as a property:

LoggedInUser.Current

This has several properties including the userId and role list.

I've looked at using initParams, but haven't been very successful there (edit: I couldn't do it dynamically originally). I've created a simple POCO entity with a [Key] attribute, but I need to at least be able to pass the userId from the aspx page to the imbedded silverlight.

What is the easiest way to pass a dynamic object from aspx to silverlight 4?

Thank you slugster:

Set up the initParams on the aspx page
<param name="initParams" value="<%=InitParam%>"/>
in Code behind:

private void LoadSilverlightParams()
    {
        LoggedInUser user = LoggedInUser.Current;
        InitParam = "UserId=" + user.PersonId.ToString() + ",";
        InitParam += "OrganizationId=" + user.OrganizationId.ToString() + ",";
        InitParam += "RoleList=";
        foreach(string s in user.Roles)
        {
            InitParam += s + "|";
        }
        InitParam.Remove(InitParam.Count() - 1);
    }

(not pretty, but it works) Then used Slugster's example to use the values on the Silverlight side.

Warning: Passing user information via init params exposes the info as plain text to the user viewing the page (they just have to view the source). We ended up using an authentication domain service and using the same user object as the aspx

Answer 1

In the constructor of the startup object of your silverlight application you could read the query string of the aspx page hosting the silverlight app.

So you could pass the id via a query string and then use that id to call a wcf service which would return your POCO or any object u can serialize through the wire.

an example of getting the query string is shown below.

string val = System.Windows.Browser.HtmlPage.Document.QueryString["id"];

Hope this helps

Answer 2

You have 3 basic options:

• use the initParams parameter of the Silverlight object plugin
• use the Silverlight-javascript bridge to access values held within the aspx part of the page
• use a WCF (or asmx) webservice call to get the info you require

With initParams, you send through a comma delimited list of values which becomes available as the key/value collection StartupEventArgs parameter in the Application_Startup part of the Silverlight control. You can then just check for the existence of a specific key and then rehydrate a data object with the values you find:

private void Application_Startup(object sender, StartupEventArgs e)
{
    if (e.InitParams != null && e.InitParams.Count > 0)
    {
        foreach (string key in e.InitParams.Keys)
        {
            switch (key.ToLower())
            {
                case "user":
                    MyAppDetails.UserId = int.Parse(e.InitParams["user"]);
                    break;

                case "year":
                    MyAppDetails.SelectedYear = int.Parse(e.InitParams["year"]);
                    break;

                case "userlogonname":
                    MyAppDetails.UserLogonName = e.InitParams["userlogonname"];
                    break;

                case "currentyear":
                    MyAppDetails.CurrentYear = int.Parse(e.InitParams["currentyear"]);
                    break;

                case "debuglevel":
                    MyAppDetails.DebugLevel = (AppDebugLevel)int.Parse(e.InitParams["debuglevel"] ?? "1");
                    break;

                case "uitheme":
                    MyAppDetails.UITheme = e.InitParams["uitheme"];
                    break;

            }
        }

    }

    this.RootVisual = new MainPage();
}

(MyAppDetails is a globally accessible (within the SL app) static object). Using this method i can dynamically populate the initParams at runtime within the aspx page.

A couple of links to get you started are some former answers of mine here and here, and an answer to my own question on the same topic a long time ago here (this answer is more oriented towards the WCF style of doing things).