Error In Vs2012

Hi.
I Use Entity Model In Project But Happend Errors
Error    2    The type or namespace name 'Infrastructure' does not exist in the namespace 'System.Data.Entity' (are you missing an assembly reference?)    E:\ProgDot\Hamayesh\DesktopModules\TMMeetings\data.Context.cs    14    30    TMMeetings
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Error    3    The type or namespace name 'DbContext' could not be found (are you missing a using directive or an assembly reference?)    E:\ProgDot\Hamayesh\DesktopModules\TMMeetings\data.Context.cs    16    45    TMMeetings
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Error    5    The type or namespace name 'DbModelBuilder' could not be found (are you missing a using directive or an assembly reference?)    E:\ProgDot\Hamayesh\DesktopModu ...