Microsoft.Silverlight.CSharp.targets was not found

Scenario:
Opened an old silverlight project and got following error.

The imported project "C:\Program Files (x86)\MSBuild\Microsoft\Silverlight\v4.0\Microsoft.Silverlight.CSharp.targets" was not found. Confirm that the path in the <import> declaration is correct, and that the file exists on disk.

Solution:
1. Download Silverlight4_Tools from MS Web site and install it

2. Close VS 2010 and start again to load the project

Silverlight parameters

Scenario:
Silverlight and SharePoint 2010 is great combination. Here's a quick post of how to pass parameters to Silverlight and consume them in Silverlight.

Solution #1: (Initialization Parameters)
This is most commonly used way to pass the values. This is how we declare it.

ASPX(C#)

<asp:Silverlight ID="Xaml1" runat="server" 
    Source="~/ClientBin/InitParamsMgr.xap" 
    MinimumVersion="2.0.31005.0" Width="100%" Height="100%"
    InitParameters="param1=value1,param2=value2">
</asp:silverlight>

HTML

<object id="SilverlightPlugin1" width="300" height="300"
    data="data:application/x-silverlight-2," 
    type="application/x-silverlight-2" >
    <param name="source" value="SilverlightApplication1.xap"/>
    <param name="InitParams" value="param1=value1,param2=value2" />
    <!-- Display installation image. -->
    <a href="http://go.microsoft.com/fwlink/?LinkID=149156&v=4.0.50401.0" 
        style="text-decoration: none;">
        <img src="http://go.microsoft.com/fwlink/?LinkId=161376" 
            alt="Get Microsoft Silverlight" 
            style="border-style: none"/>
    </a>
</object>

How to use it in Silverlight:
1. Add the following code Application_Startup method.

private void Application_Startup(object sender, StartupEventArgs e)
      {
          if (e.InitParams != null)
          {
              foreach (var item in e.InitParams)
              {
                  this.Resources.Add(item.Key, Uri.UnescapeDataString(item.Value));              }
          }
          this.RootVisual = new MainPage();
      }

2. Open MainPage.xaml.cs and add the following method

private string GetParam(string p)
      {
          if (App.Current.Resources[p] != null)
              return App.Current.Resources[p].ToString();
          else return string.Empty;
      }

3. Use the following code to read the parameter value

string param1value = GetParam("param1");

Solution #2: ( Query Parameters )
How to use it in Silverlight:
1. Add the following code Application_Startup method.

private void Application_Startup( object sender, StartupEventArgs e ){  
    this.RootVisual = new MainPage();
    string queryParam = HtmlPage.Document.QueryString["key"];
    this.Resources.Add( <resourcekey>, queryParam );
}

2. Use the following code to read the parameter value
in XAML

<silverlightcontrol property={StaticResource ResourceKey} />

or in C#

object parameter = ((App)Application.Current).Resources[<Resourcekey>];

Article:
How to pass initialize parameters..

Related and Referred Articles:
MSDN
Decoding paramters

Current Web Url in Silverlight

Scenario:
Client Object Model and Silverlight is best combo which I use often and always get this question on how to get the Current SharePoint Web Url from within Silverlight without passing it from initparam's manually.

Answer is simple

Steps:
1. Open App.xaml.cs and add the following using statements to the top of the file

using Microsoft.SharePoint.Client;
using System.Threading;

2. Add the following code to the beginning of the Application_Startup method.

ApplicationContext.Init(e.InitParams, SynchronizationContext.Current);

3. Open MainPage.xaml.cs and add the following using statement to the top of the file

using Microsoft.SharePoint.Client;

4. Use the following code to get the client context for current web

ClientContext context = new ClientContext(ApplicationContext.Current.Url);
context.Load(context.Web);

List listSharedDocuments = context.Web.Lists.GetByTitle("Shared Documents");
context.Load(listSharedDocuments);

Unable to open Silverlight 4 projects in VS2010

Scenario:
I was trying new features of Silverlight 4 and got following error opening the project

The imported project "C:\Program Files (x86)\MSBuild\Microsoft\Silverlight\v4.0\Microsoft.Silverlight.CSharp.targets" was not found.
Confirm that the path in the declaration is correct, and that the file exists on disk.

Solution:
Reason is simple Visual Studio 2010 is missing the support for Silverlight 4, so you will need Silverlight 4 for VS 2010 to be able to make it work

1. Google for 'Web Installer 2.0'
2. Download and install it.
3. Now launch the Web Installer and look for Silverlight 4 add-on for Visual Studio 2010.
4. Select it and install it.

Just in case Web Installer is not able to install the component or you want to download the Silverlight 4 tools for VS 2010. You can get it from this here

Silverlight security error connecting SharePoint

Scenario:
Wrote a small Silverlight application which was trying to display the title of the site using Client Object Model and to my surprise I got the following error :

{System.Security.SecurityException ---> System.Security.SecurityException: Security error.
at System.Net.BrowserHttpWebRequest.InternalEndGetResponse(IAsyncResult asyncResult)
at System.Net.BrowserHttpWebRequest.<>c__DisplayClass5.b__4(Object sendState)
at System.Net.AsyncHelper.<>c__DisplayClass2.b__0(Object sendState)
--- End of inner exception stack trace ---
at System.Net.AsyncHelper.BeginOnUI(SendOrPostCallback beginMethod, Object state)
at System.Net.BrowserHttpWebRequest.EndGetResponse(IAsyncResult asyncResult)
at System.Net.WebClient.GetWebResponse(WebRequest request, IAsyncResult result)
at System.Net.WebClient.OpenReadAsyncCallback(IAsyncResult result)}

Solution:
This can be because of few reasons

1. Make sure the web URL used to create the Client context object exist and brows-able.

2. This might be because of missing client policy access file missing for the SharePoint Web Application not allowing you to connect. Create a new XML file named ClientAccessPolicy.xml with content below and save it to 'C:\inetpub\wwwroot\VirtualDirectories\80'

Note : Update policy file and port number as needed.

ClientAccessPolicy.xml:

<?xml version="1.0" encoding="utf-8" ?> 
  <access-policy>
    <cross-domain-access>
      <policy>
        <allow-from http-request-headers="*">
           <domain uri="*" /> 
        </allow-from>
        <grant-to>
          <resource path="/" include-subpaths="true" /> 
        </grant-to>
     </policy>
   </cross-domain-access>
  </access-policy>

Once you have the file copied to right location, do an IISReset and make sure you can access the file using following url :

http://servername:portno/clientaccesspolicy.xml
Note
This setting is only for Development Environment. Read the following article how to tweak the policy file for production environment.

Article:MSDN

Error referencing SharePoint Client DLLs in Silverlight

Scenario:
I build up a new VM and was experimenting with Silverlight and SharePoint. I created a new Silverlight Application Project in Visual Studio. Then I tried adding the client object model dlls.

Microsoft.SharePoint.Client.Silverlight.dll
and
Microsoft.SharePoint.Client.Silverlight.Runtime.dll

located at "C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\14\TEMPLATE\LAYOUTS\ClientBin" and surprisingly got this



Sometime your project build just fine but you get referencing error at run time, something like this.



Solution:
Two step solution was
1. Copy both the binaries from
"C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\14\TEMPLATE\LAYOUTS\ClientBin" to "C:\SilverlightClientOM" folder.

2. Reference from the new folder

What is SilverLight ?

Microsoft Silverlight is a cross-browser, cross-platform, and cross-device plug-in for delivering the next generation of .NET based media experiences and rich interactive applications for the Web. Silverlight offers a flexible programming model that supports AJAX, VB, C#, IronPython, and IronRuby, and integrates with existing Web applications. By using Expression Studio and Visual Studio, designers and developers can collaborate more effectively using the skills they have today to light up the Web of tomorrow. By leveraging Silverlight's support for .NET, High Definition video, cost-effective advanced streaming, unparalleled high-resolution interactivity with Deep Zoom technology, and controls, businesses can reach out to new markets across the Web, desktop, and devices.