If you get the following problem in Expression Blend 3.0.1927.0: “Unsupported project”
Figure: Error messages in Expression Blend
Add the following pieces manually to your project file (.proj)
<PropertyGroup Condition="'$(MSBuildToolsVersion)' == '3.5'">
<TargetFrameworkVersion>v3.5</TargetFrameworkVersion>
</PropertyGroup>
and (not sure if that is actually needed…)
<ExpressionBlendVersion>3.0.1927.0</ExpressionBlendVersion>
Figure: Applied changes to the .proj file
Reason: Expression Blend is not .NET 4 aware, so it needs this switch at the top of the project file