title: Why is there an Error in ef Add-Migration
body: <p>I have several class files. Now I am adding a new model class and tried to type <code>add-migration InitialCreate</code> but am getting the following error:</p>
  
  <pre><code>PM&gt; 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 &lt;&lt;&lt;&lt; ((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 &lt;&lt;&lt;&lt; (
      + 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 &lt;&lt;&lt;&lt; (
      + CategoryInfo          : NotSpecified: (:) [], MethodInvocationException
      + FullyQualifiedErrorId : DotNetMethodException
  
  PM&gt;
  </code></pre>