----------------------------------------------------------------------------------------- Entity Framework 5 Recommended for .NET Framework 4.5 Projects ----------------------------------------------------------------------------------------- You have installed EF 4.3 in a project that targets .NET Framework 4.5. There are some known issues using EF 4.x in a .NET 4.5 project. We recommend installing a pre-release version of EF 5, which is designed to work with .NET 4.5 1) Open package manager console Tools -> Library Package Manager -> Package Manager Console 2) Use the following command to install the latest pre-release package Install-Package EntityFramework -IncludePreRelease ----------------------------------------------------------------------------------------- Known Issues with Entity Framework 4.x and .NET Framework 4.5 ----------------------------------------------------------------------------------------- Entity Framework 4.1 thru 4.3 included additional data annotations in the System.ComponentModel.DataAnnotations namespace in the EntityFramework assembly. In .NET 4.5 these annotations were moved to be part of the .NET Framework in the System.ComponentModel.DataAnnotations.Schema namespace of the System.ComponentModel.DataAnnotations.dll assembly. If you are using EF 4.x and targeting .NET 4.5 this results in two data annotations with the same name in different assemblies. Because the annotations in the .NET Framework are in a different namespace we were not able to use type forwarding to avoid this conflict. It is possible to use EF 4.x on .NET 4.5 but we recommend using the latest pre-release version of EF 5. If you are not using the affected data annotations there is no impact on your code. If you are using the data annotations in a C# project you can use the extern modifier to ensure your code uses the annotations from EntityFramework.dll (http://msdn.microsoft.com/en-us/library/e59b22c5(v=VS.80).aspx). If you use the new annotations from the System.ComponentModel.DataAnnotations.dll assembly in .NET 4.5 they will not be processed by Code First. The affected annotations are: - Column - ComplexType - DatabaseGenerated - DatabaseGeneratedOption - ForeignKey - InverseProperty - MaxLength - MinLength - NotMapped - Table