Why is there an Error in ef Add-Migration

Question

I have several class files. Now I am adding a new model class and tried to type add-migration InitialCreate but am getting the following error:

PM> add-migration InitialCreate
Exception calling "LoadFrom" with "1" argument(s): "Could not load file or assembly 'file:///C:\Users\user\Documents\Visual Studio 2013\Pro
jects\DigitalHealthWebPrev\packages\EntityFramework.6.1.3\tools\EntityFramework.PowerShell.Utility.dll' or one of its dependencies. Operati
on is not supported. (Exception from HRESULT: 0x80131515)"
At C:\Users\user\Documents\Visual Studio 2013\Projects\DigitalHealthWebPrev\packages\EntityFramework.6.1.3\tools\EntityFramework.psm1:780 c
har:62
+     $utilityAssembly = [System.Reflection.Assembly]::LoadFrom <<<< ((Join-Path $ToolsPath EntityFramework.PowerShell.Utility.dll))
    + CategoryInfo          : NotSpecified: (:) [], MethodInvocationException
    + FullyQualifiedErrorId : DotNetMethodException

You cannot call a method on a null-valued expression.
At C:\Users\user\Documents\Visual Studio 2013\Projects\DigitalHealthWebPrev\packages\EntityFramework.6.1.3\tools\EntityFramework.psm1:781 c
har:50
+     $dispatcher = $utilityAssembly.CreateInstance <<<< (
    + CategoryInfo          : InvalidOperation: (CreateInstance:String) [], RuntimeException
    + FullyQualifiedErrorId : InvokeMethodOnNull

Exception calling "CreateInstanceFrom" with "8" argument(s): "Could not load file or assembly 'file:///C:\Users\user\Documents\Visual Studi
o 2013\Projects\DigitalHealthWebPrev\packages\EntityFramework.6.1.3\tools\EntityFramework.PowerShell.dll' or one of its dependencies. Opera
tion is not supported. (Exception from HRESULT: 0x80131515)"
At C:\Users\user\Documents\Visual Studio 2013\Projects\DigitalHealthWebPrev\packages\EntityFramework.6.1.3\tools\EntityFramework.psm1:809 c
har:31
+     $domain.CreateInstanceFrom <<<< (
    + CategoryInfo          : NotSpecified: (:) [], MethodInvocationException
    + FullyQualifiedErrorId : DotNetMethodException

PM>

Solution 1

Using the Package Manager, you need to re-install Entity Framework:

Uninstall-Package EntityFramework -Force

Then install it for each project:

Install-Package EntityFramework

Then do not forget to restart the studio.

https://stackoverflow.com/a/14994432/1845408

Solution 2

Used the command EntityFramework6\add-migration {migration name} instead. Microsoft changed the name of the command.

Solution 3

Just restart the visual studio and clean the solution and rebuild it again.

Solution 4

In my case, it was a different entity-framework version between main project and the project containing DbContext. I just updated version of package in both projects to v6.4.4

Solution 5

I had a slightly different case today, I'm wirting the details here in case that might help somebody. The error was referencing one of my assemblies instead, on which the assembly containing the EF DbContext was depending.
I solved it setting the referenced assembly to "Copy Local" "true" so it'd make a local copy when building for migrations and therefore be able to find it.

View more solutions