reference project issue when convert VS2008 to VS2010

I have a shared project (C#) used by several other projects. In VS2008, everything compiles fine. Now I convert all to VS2010, then two referencing projects complain that the shared dll not found

<Window x:Class="MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
    xmlns:sharedC="clr-namespace:Shared.Converter;assembly=Shared" 
    <Window.Resources>开发者_如何学编程;
        <ResourceDictionary>
            <sharedC:BooleanToHiddenVisibility x:Key="boolToVis"/>

...

VS2010 compiler complaint about sharedC: BooleanToHiddenVisibilty not found the error msg is: The tag 'BooleanToHiddenVisibility' does not exist in XML namespace 'clr-namespace:Shared.Convert; assembly=Shared'. Line 14 position 14

I compiled shared.dll first and compilation is successful. I removed shared project from reference and add it back. Still the same error I checked the path of referenced shared.dll, it is correct

Not sure what I missed.

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Found it. After conversion, project used to target .NET framework 3.5, after conversion, it is changed to target .NET framework 3.5 client profile. I change it back to .NET 3.5 framework and it compiles successfully