Public/ConvertTo-String.ps1

<#
    .SYNOPSIS
        Converts a base64 encoded string to a string.
     
    .DESCRIPTION
        Converts a base64 encoded string to a string.
     
    .PARAMETER Base64EncodedString
        A Base64 Encoded String
     
    .PARAMETER MemoryStream
        A MemoryStream object for conversion.
     
    .PARAMETER Encoding
        The encoding to use for conversion.
        Defaults to UTF8.
        Valid options are ASCII, BigEndianUnicode, Default, Unicode, UTF32, UTF7, and UTF8.
     
    .EXAMPLE
        ConvertTo-String -Base64EncodedString 'QSBzdHJpbmc='
         
        A string
     
    .EXAMPLE
        ConvertTo-String -Base64EncodedString 'QSBzdHJpbmc=','QW5vdGhlciBzdHJpbmc='
 
        A string
        Another string
     
    .EXAMPLE
        'QSBzdHJpbmc=' | ConvertTo-String
 
        A string
 
    .EXAMPLE
        'QSBzdHJpbmc=','QW5vdGhlciBzdHJpbmc=' | ConvertTo-String
 
        A string
        Another string
 
    .EXAMPLE
        $string1 = 'A string'
        $stream1 = [System.IO.MemoryStream]::new()
        $writer1 = [System.IO.StreamWriter]::new($stream1)
        $writer1.Write($string1)
        $writer1.Flush()
 
        $string2 = 'Another string'
        $stream2 = [System.IO.MemoryStream]::new()
        $writer2 = [System.IO.StreamWriter]::new($stream2)
        $writer2.Write($string2)
        $writer2.Flush()
 
        ConvertTo-String -MemoryStream $stream1,$stream2
 
        A string
        Another string
 
    .EXAMPLE
        $string1 = 'A string'
        $stream1 = [System.IO.MemoryStream]::new()
        $writer1 = [System.IO.StreamWriter]::new($stream1)
        $writer1.Write($string1)
        $writer1.Flush()
 
        $string2 = 'Another string'
        $stream2 = [System.IO.MemoryStream]::new()
        $writer2 = [System.IO.StreamWriter]::new($stream2)
        $writer2.Write($string2)
        $writer2.Flush()
 
        $stream1,$stream2 | ConvertTo-String
 
        A string
        Another string
 
    .OUTPUTS
        [String[]]
 
    .LINK
        http://convert.readthedocs.io/en/latest/functions/ConvertTo-String/
#>

function ConvertTo-String
{
    [CmdletBinding(
        DefaultParameterSetName = 'Base64String',
        HelpUri = 'http://convert.readthedocs.io/en/latest/functions/ConvertFrom-StringToMemoryStream/')]
    param
    (
        [Parameter(
            Mandatory = $true,
            ValueFromPipeline = $true,
            ValueFromPipelineByPropertyName = $true,
            ParameterSetName = 'Base64String')]
        [ValidateNotNullOrEmpty()]
        [String[]]
        $Base64EncodedString,

        [Parameter(
            Mandatory = $true,
            ValueFromPipeline = $true,
            ValueFromPipelineByPropertyName = $true,
            ParameterSetName = 'MemoryStream')]
        [ValidateNotNullOrEmpty()]
        [System.IO.MemoryStream[]]
        $MemoryStream,
        
        [Parameter(ParameterSetName = 'Base64String')]
        [ValidateSet('ASCII', 'BigEndianUnicode', 'Default', 'Unicode', 'UTF32', 'UTF7', 'UTF8')]
        [String]
        $Encoding = 'UTF8'
    )

    begin
    {
        $userErrorActionPreference = $ErrorActionPreference
    }
    
    process
    {
        switch ($PSCmdlet.ParameterSetName)
        {
            'Base64String'
            {
                $InputObject = $Base64EncodedString
                $Function = 'ConvertFrom-Base64ToString'
                $splat = @{
                    Encoding = $Encoding
                }
                break
            }

            'MemoryStream'
            {
                $InputObject = $MemoryStream
                $Function = 'ConvertFrom-MemoryStreamToString'
                $splat = @{
                }
                break
            }

            default
            {
                Write-Error -Message 'Invalid ParameterSetName' -ErrorAction $userErrorActionPreference
                break
            }
        }

        if ($InputObject)
        {
            $InputObject | & $Function @splat -ErrorAction $userErrorActionPreference
        }
    }
}