Get-DirectoryHash.psm1

function Get-DirectoryHash {
    [CmdletBinding()]
    param(
        [System.IO.DirectoryInfo]
        $Path
        ,
        [switch]
        $IncludeName
    )

    begin {
        function Get-StringHash {
            [CmdletBinding()]
            PARAM(
                [Parameter(Position = 0, Mandatory = $true, ValueFromPipeline = $true, ValueFromPipelineByPropertyName = $true)]
                [AllowNull()]
                [AllowEmptyString()]
                [String]$String
                ,
                [Parameter(Position = 1, Mandatory = $false, ValueFromPipeline = $true, ValueFromPipelineByPropertyName = $true)]
                [ValidateSet('SHA', 'SHA1', 'System.Security.Cryptography.SHA1', 'System.Security.Cryptography.HashAlgorithm', 'MD5', 'System.Security.Cryptography.MD5', 'SHA256', 'SHA-256', 'System.Security.Cryptography.SHA256', 'SHA384', 'SHA-384', 'System.Security.Cryptography.SHA384', 'SHA512', 'SHA-512', 'System.Security.Cryptography.SHA512')]
                [String]$HashName = "MD5"
            )
	
            begin {
                $StringBuilder = New-Object System.Text.StringBuilder
            }
	
            process {
                if ($String.Trim().Length) {
                    [System.Security.Cryptography.HashAlgorithm]::Create($HashName).ComputeHash([System.Text.Encoding]::UTF8.GetBytes($String)) | ForEach-Object {
                        [Void]$StringBuilder.Append($_.ToString("x2"))
                    }
                    $StringBuilder.ToString()
                }
            }
	
            end {
            }
        }
    }

    process {
        $Items = Get-ChildItem -Path $Path -File -Recurse | ForEach-Object {
            $Item = $_
            $Item | Add-Member -MemberType ScriptProperty -Name RelativePath -Value { ($this.DirectoryName -replace "^$([regex]::Escape($Path))", '\') -replace '\\', '\' } -Force
            $Item | Add-Member -MemberType ScriptProperty -Name MD5Hash -Value { Get-FileHash -Path $this.FullName -Algorithm MD5 | Select-Object -ExpandProperty Hash } -Force
            $Item | Add-Member -MemberType ScriptProperty -Name MD5FileName -Value { "$($this.MD5Hash)_$($this.Name)" } -Force
            $Item | Add-Member -MemberType ScriptProperty -Name MD5RelativePath -Value { Join-Path -Path $this.RelativePath -ChildPath $this.MD5Hash } -Force
            $Item | Add-Member -MemberType ScriptProperty -Name MD5RelativeUniquePath -Value { Join-Path -Path $this.RelativePath -ChildPath $this.MD5FileName } -Force
            $Item
        } | Sort-Object -Property FullName
        
        if ($IncludeName) {
            $StringToHash = $Items.MD5RelativeUniquePath | Out-String
        } else {
            $StringToHash = $Items.MD5RelativePath | Out-String
        }
        Get-StringHash -String $StringToHash -HashName MD5
    }

    end {
    }
}