Powershell load dll got error: Add-Type : Could not load file or assembly 'WebDriver.dll' or one of its dependencies. Operation is not supported

I want to use PowerShell with selenium and download selenium from http://www.java2s.com/Code/Jar/s/Downloadseleniumremotedriver2350jar.htm . When I try to load one of the dlls, I got errors. Hope someone can help me with it.

This is my system info.

OS Name:                   Microsoft Windows 7 Enterprise
OS Version:                6.1.7601 Service Pack 1 Build 7601
OS Manufacturer:           Microsoft Corporation

This is my PowerShell info.

PS C:\Users\test\Downloads\selenium-dotnet-2.35.0\net40> $psversiontable

Name                           Value
----                           -----
PSVersion                      4.0
WSManStackVersion              3.0
SerializationVersion           1.1.0.1
CLRVersion                     4.0.30319.18052
BuildVersion                   6.3.9421.0
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0}
PSRemotingProtocolVersion      2.2


PS C:\Users\test\Downloads\selenium-dotnet-2.35.0\net40>

This is the errors I got when trying to load the dll.

    PS C:\Users\test\Downloads\selenium-dotnet-2.35.0\net40> Add-Type -Path .\WebDriver.dll
    Add-Type : Could not load file or assembly 'file:///C:\Users\test\Downloads\selenium-dotnet-2.35.0\net40\WebDriver.dll' or one of its dependencies. Operation is
    not supported. (Exception from HRESULT: 0x80131515)
    At line:1 char:1
    + Add-Type -Path .\WebDriver.dll
    + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        + CategoryInfo          : NotSpecified: (:) [Add-Type], FileLoadException
        + FullyQualifiedErrorId : System.IO.FileLoadException,Microsoft.PowerShell.Commands.AddTypeCommand

    PS C:\Users\test\Downloads\selenium-dotnet-2.35.0\net40> [reflection.assembly]::LoadFrom(".\WebDriver.dll")
    Exception calling "LoadFrom" with "1" argument(s): "Could not load file or assembly 'file:///C:\Users\test\WebDriver.dll' or one of its dependencies. The system
    cannot find the file specified."
    At line:1 char:1
    + [reflection.assembly]::LoadFrom(".\WebDriver.dll")
    + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        + CategoryInfo          : NotSpecified: (:) [], MethodInvocationException
        + FullyQualifiedErrorId : FileNotFoundException

    PS C:\Users\test\Downloads\selenium-dotnet-2.35.0\net40> [reflection.assembly]::LoadFrom("WebDriver.dll")
    Exception calling "LoadFrom" with "1" argument(s): "Could not load file or assembly 'file:///C:\Users\test\WebDriver.dll' or one of its dependencies. The system
    cannot find the file specified."
    At line:1 char:1
    + [reflection.assembly]::LoadFrom("WebDriver.dll")
    + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        + CategoryInfo          : NotSpecified: (:) [], MethodInvocationException
        + FullyQualifiedErrorId : FileNotFoundException

    PS C:\Users\test\Downloads\selenium-dotnet-2.35.0\net40> [reflection.assembly]::LoadFrom("C:\Users\test\Downloads\selenium-dotnet-2.35.0\net40\WebDriver.dll")
    Exception calling "LoadFrom" with "1" argument(s): "Could not load file or assembly 'file:///C:\Users\test\Downloads\selenium-dotnet-2.35.0\net40\WebDriver.dll' or
    one of its dependencies. Operation is not supported. (Exception from HRESULT: 0x80131515)"
    At line:1 char:1
    + [reflection.assembly]::LoadFrom("C:\Users\test\Downloads\selenium-dotnet-2.35.0 ...
    + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        + CategoryInfo          : NotSpecified: (:) [], MethodInvocationException
        + FullyQualifiedErrorId : FileLoadException

    PS C:\Users\test\Downloads\selenium-dotnet-2.35.0\net40> [reflection.assembly]::LoadFile("C:\Users\test\Downloads\selenium-dotnet-2.35.0\net40\WebDriver.dll")
    Exception calling "LoadFile" with "1" argument(s): "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
    information."
    At line:1 char:1
    + [reflection.assembly]::LoadFile("C:\Users\test\Downloads\selenium-dotnet-2.35.0 ...
    + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        + CategoryInfo          : NotSpecified: (:) [], MethodInvocationException
        + FullyQualifiedErrorId : NotSupportedException

    PS C:\Users\test\Downloads\selenium-dotnet-2.35.0\net40>

If you downloaded the .DLLs from the internet, Powershell by default will not trust them. You can do one of two things here:

1. Unblock the content. Here's a guide with some elaboration on the problem, but essentially you just need to right-click on the downloaded file, select Properties, and click 'Unblock' in the general tab. You can unblock content directly from powershell by using the Unblock-File cmdlet.
2. Change your execution policy. This can also allow malicious scripts that you download to run, so be cautious.

Specifically reviewing and unblocking content you trust seems the better route, especially for your case since you seem like you would only be doing this once and you trust the package.

Edit: If that didn't solve that, the other experience I've had with this type of error is when Powershell didn't the same version of the .NET runtime as the assembly. See this question for some context, where Powershell 2.0 ran the .NET 2 runtime and the asker needed .NET 4 for some assemblies.

You're not using the same version of PS so your mileage may vary, but I would try creating/editing a config file per the linked answer to support the runtime of the DLLs you are using.