PowerShell Add-Type Error: Could not load file or assembly XXX or one of its dependencies.

If you are attempting to run the PowerShell command Add-Type with a Path parameter that references an assembly which has been emailed or downloaded from the internet (e.g. Add-Type -Path "C:\Microsoft.SharePoint.Client.dll") then it is likely that you will encounter the following error:

Could not load file or assembly ‘file:///’ or one of its dependencies. Operation is not supported. (Exception from HRESULT: 0x80131515)


To confirm that the following steps are appropriate. Check the inner exception:

PS> $error[0].Exception.InnerException

“An attempt was made to load an assembly from a network location which would have caused the assembly to be
sandboxed in previous versions of the .NET Framework. This release of the .NET Framework does not enable
CAS policy by default, so this load may be dangerous. If this load is not intended to sandbox the assembly,
please enable the loadFromRemoteSources switch. See http://go.microsoft.com/fwlink/?LinkId=155569 for more

Not using SharePoint Client Components?

First check the execution policy under which PowerShell is running. This can be done by running the Get-ExecutionPolicy cmdlet. If you are not running under an Unrestricted policy, try running the Add-type cmdlet after setting the execution policy to Unrestricted (Set-ExecutionPolicy “Unrestricted”). If this resolves the issue then you’ll need to look into getting the assembly signed by a trusted publisher if you can’t continue to run PowerShell in this lowered state of security.

Next ensure that the assembly hasn’t been blocked. The easiest way to achieve this is by right-clicking on the assembly and checking on the General tab that there isn’t the option to unblock the assembly at bottom of the dialog. There is also the Unblock-File cmldlet to achieve this action via PowerShell.

Unblocking an assembly
Unblocking an assembly

Finally, PowerShell supports a config file which by default is not present. It allows configuration of a few things like the .NET versions which are supported and, importantly for us, whether or not PowerShell is allowed to load from remote sources. In order to add/update this file, ensure that you are logged in as a local administrator. The config file needs to reside adjacent to the PowerShell exe file. So, by default, it ought to be created here: C:\Windows\System32\WindowsPowerShell\v1.0\powershell.exe.config

Note: Do not confuse this with powershell_ise.exe.config although you may want to update this as well if you use ISE.

The content of the powershell.exe.config should be as follows. If you already have a file present, ensure that you merge the XML rather than just replacing it.

<?xml version="1.0"?>
  <startup useLegacyV2RuntimeActivationPolicy="true">
    <supportedruntime version="v4.0.30319"/>
    <supportedruntime version="v2.0.50727"/>
    <loadfromremotesources enabled="true"/>

Using SharePoint Client Components?

If you are adding the SharePoint Client assemblies required for the execution of CSOM requests then you should take a different approach. Rather than bundling these assemblies with your script, instead insure that the correct SharePoint Client Components package is installed on the executing machine and reference the assemblies from their default location:

Download Client Components:
SharePoint Online Client Components
SharePoint 2013 Client Components

Reference Accordingly:
C:\Program Files\Common Files\microsoft shared\Web Server Extensions\16\ISAPI\assembly.dll
C:\Program Files\Common Files\microsoft shared\Web Server Extensions\15\ISAPI\assembly.dll


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