C# – Getting data out of a Silverlight control

You can use JavaScript:

<script language="javascript">
window.opener.location.reload();
self.close();
</script>

The above code shows how to close the 'opener' window, but it should give you the general idea. (This code is in the Popup window). You can use the same method to pass values to the 'opener' window by calling JavaScript function within it.

<script language="javascript">
window.opener.functionA('ABC123');    
</script>

If you want to pass a variable from your ASP into the JavaScript function, use:

window.opener.functionA('<%=userId%>');

or

var userId = '<%=userId%>';
window.opener.functionA( userId );

Hope that helps!

I suggest that you try out Silverlight to get a feel for how powerful that environment is. Personally I think that jQuery is nice, but you get a much more controlled and rich environment if you use Silverlight.

1. Assuming you are using Visual Studio 2008 download Microsoft® Silverlight™ 3 Tools for Visual Studio 2008 SP1. This will enable you to create Silverlight projects in Visual Studio. You can also use Expression Blend to author Silverlight applications, but as long as you are comfortable writing XAML without a visual designer you might find Visual Studio a bit more mature from a developer standpoint.
2. If you want to you can try Microsoft .NET RIA Services July 2009 Preview. It is a very powerful environment enabling your Silverlight application to seamlessly work with your data-model on your ASP.NET server. In particular there is very good integration with LINQ to SQL and the ADO.NET Entity Framework. However, if you are new to Silverlight you might find the learning curve a bit steep. You will have to load query operations in order to execute them asynchronously etc. Have a look at the Word document found at the download location to get you started.
3. As others have suggested you can simply hide an HTML form in the web page hosting the Silverlight control and then use the HtmlPage object from within Silverlight to access the browser DOM to submit your form.
4. If you want to do POST operations from within Silverlight without using a web service framework like .NET RIA Services or WCF you can use a WebClient or HttpWebRequest object. Silverlight 3 has two HTTP stacks and the default is to use the browser stack ensuring that browser cookies (e.g. forms authentication cookies) are used in your request.
5. Your form has a complex interaction logic and I strongly suggest that you have a look at the MVVM pattern. In Silverlight you create a view-model containing all relevant data for the form. Relevant data not only include the values of the fields in the form but also information about which controls are enabled, selection information if that applies etc. You then data-bind the form (view) to the view-model and by implementing INotifyPropertyChanged in the view-model you get a complex interaction logic if not for free at least in a way that is reasonable easy to handle as a developer. The partial client-side classes generated for you in .NET RIA Services are particular good candidates for view-models making it straightforward to apply the MVVM pattern within that framework.