Cannot Build Expression Blend 4 / Silverlight 4 Project in Visual Studio 2010

Just had this problem: Trying to build an Expression Blend 4 Silverlight 4 project in Visual Studio 2010 on a machine that does not have Expression Blend 4 installed on it threw these errors:

The property 'Triggers' does not exist on the type 'Grid' in the XML namespace 'http://schemas.microsoft.com/expression/2010/interactivity'.   
The tag 'EventTrigger' does not exist in XML namespace 'http://schemas.microsoft.com/expression/2010/interactivity'.   
The tag 'ControlStoryboardAction' does not exist in XML namespace 'http://schemas.microsoft.com/expression/2010/interactions'.   
The tag 'EventTrigger' does not exist in XML namespace 'http://schemas.microsoft.com/expression/2010/interactivity'.   
The tag 'ControlStoryboardAction' does not exist in XML namespace 'http://schemas.microsoft.com/expression/2010/interactions'.   

In order to fix this, I just had to install the Microsoft Expression Blend Software Development Kit (SDK) for Silverlight 4

Unable To Open Silverlight 4 Project In Visual Studio 2010

Just had this issue: Opening a project created on another machine threw an error in Visual Studio 2010. The output window contained this message:

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.

The problem is that I didn’t have the Microsoft Silverlight 4 Tools for Visual Studio 2010 installed. This can be downloaded from here: http://www.microsoft.com/downloads/details.aspx?FamilyID=eff8a0da-0a4d-48e8-8366-6ddf2ecad801&displaylang=en

Unable to start debugging. The Silverlight managed debugging package isn’t installed.

Just had this problem – Installed Visual Studio 2010 (which installs Silverlight 4), then used Visual Studio 2008 to open a Silverlight 3 project, tried to debug it, and POW!

I fixed it by installing the Silverlight Windows Developer Runtime, as linked to from http://www.silverlight.net/getstarted/