ef添加迁移错误

我有几个类文件。但现在我添加了新的模型类，并尝试输入添加迁移InitialCreate。但是我收到以下错误。ef添加迁移错误

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>

来源

2015-05-09 noushad mohammed