.NET Assembly loader for Powershell. Based on https://gist.github.com/guitarrapc/72bffd1e1c12bec100f9#file-testmodule-psm1

LoadAssembly.ps1

function LoadAssembly {
    [CmdletBinding()]
    param (
        [Parameter(Mandatory=$true, ValueFromPipeline=$true)]
        [string[]]$asmNames,
        [string]$baseDir = $PSScriptRoot
    )
    begin {
        $domain = [System.AppDomain]::CurrentDomain
        [Reflection.Assembly[]]$asms = $domain.GetAssemblies()
        $cache = New-Object "System.Collections.Generic.HashSet[string]" (,[string[]]$asms.GetName().Name)
        
        $path = $domain.getType().Assembly.Location
        $searchPath = $baseDir,([IO.FileInfo]$path).Directory.FullName
    }
    process {
        foreach ($asmName in $asmNames) {
            LoadAssemblyInternal $asmName $searchPath $cache
        }
    }
}

function LoadAssemblyInternal([string[]]$asmNames, [string[]]$searchPath, $cache) {
    foreach ($asmName in $asmNames) {
        if (-not $cache.Contains($asmName)) {
            $path = $searchPath | ls -filter "$asmName.dll" | select -first 1
            if ($path -ne $null) {
                Write-Verbose "Try Loading: $path"
                [byte[]]$binary = [System.IO.File]::ReadAllBytes($path.FullName)
                $asm = [System.Reflection.Assembly]::Load($binary);
                $asm
                
                Write-Verbose "Loaded: $($asm.FullName)"
                
                $cache.Add($asm.GetName().Name) | Out-Null

                LoadAssemblyInternal $asm.GetReferencedAssemblies().Name $searchPath $cache
            }
        }
    }
}