Custom Assembly is added to the PowerShell Assemblies but still won't compile

Question

I am trying to run C# code with custom .NET assembly in PowerShell, but cannot get it to work.

Here is my code:

# Adding custom assemblies to the PowerShell assemblies
Add-Type -Verbose -Path "C:\MyCustomAssembly.dll"

# Adding reference of standard .NET assemblies 
$Refs = @("C:\Program Files (x86)\Reference Assemblies\Microsoft\Framework\.NETFramework\v4.5\System.Xml.dll",
"C:\Program Files (x86)\Reference Assemblies\Microsoft\Framework\.NETFramework\v4.5\System.Data.Entity.dll",
"C:\Program Files (x86)\Reference Assemblies\Microsoft\Framework\.NETFramework\v4.5\System.Runtime.Serialization.dll")

$Source = @"
using System;
using System.IO;
using System.Net;
using System.Runtime.Serialization;
using MyCustomAssembly;

namespace CSharpCode
{
    public class WebClient
    {
        public void ConsumePostMethod()
        { ... }
    }
}
"@

Add-Type -ReferencedAssemblies $Refs -TypeDefinition $Source -Language CSharp -PassThru

[CSharpCode.WebClient]::ConsumePostMethod()

And this is the error that I am getting:

Add-Type : c:\Users\MyUser\AppData\Local\Temp\znllnhvt.0.cs(5) : The type or namespace name 'MyCustomAssembly' could not be found (are you missing a using directive 
or an assembly reference?)
c:\Users\MyUser\AppData\Local\Temp\znllnhvt.0.cs(4) : using System.Runtime.Serialization;
c:\Users\MyUser\AppData\Local\Temp\znllnhvt.0.cs(5) : >>> using MyCustomAssembly;
c:\Users\MyUser\AppData\Local\Temp\znllnhvt.0.cs(6) : 
At line:109 char:1
+ Add-Type -ReferencedAssemblies $Refs -TypeDefinition $Source -Language CSharp -P ...
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidData: (c:\Users\MyUser...bly reference?):CompilerError) [Add-Type], Exception
    + FullyQualifiedErrorId : SOURCE_CODE_ERROR,Microsoft.PowerShell.Commands.AddTypeCommand

Add-Type : Cannot add type. There were compilation errors.
At line:109 char:1
+ Add-Type -ReferencedAssemblies $Refs -TypeDefinition $Source -Language CSharp -P ...
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidData: (:) [Add-Type], InvalidOperationException
    + FullyQualifiedErrorId : COMPILER_ERRORS,Microsoft.PowerShell.Commands.AddTypeCommand

Unable to find type [CSharpCode.WebClient]: make sure that the assembly containing this type is loaded.
At line:111 char:1
+ [CSharpCode.WebClient]::ConsumePostMethod()
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidOperation: (CSharpCode.WebClient:TypeName) [], RuntimeException
    + FullyQualifiedErrorId : TypeNotFound

The weird thing is if I run this command below, it shows that MyCustomAssembly.dll is loaded in the session. Can anybody help?!

[System.AppDomain]::CurrentDomain.GetAssemblies() | Where {$_.Location} | ForEach {Split-Path -Leaf $_.Location} | Sort

Accessibility.dll
MyCustomAssembly.dll
Microsoft.Build.Framework.dll
Microsoft.CSharp.dll
...

Answer 1

Add-Type does not use any currently loaded assemblies as reference implicitly. So, if you want to use any type from custom assembly in Add-Type source code, then you should add this assembly to -ReferencedAssemblies parameter explicitly.