functions/New-DbaClientAlias.ps1

function New-DbaClientAlias {
    <#
    .SYNOPSIS
    Creates/updates a sql alias for the specified server - mimics cliconfg.exe
 
    .DESCRIPTION
    Creates/updates a SQL Server alias by altering HKLM:\SOFTWARE\Microsoft\MSSQLServer\Client
 
    .PARAMETER ComputerName
    The target computer where the alias will be created
 
    .PARAMETER Credential
    Allows you to login to remote computers using alternative credentials
 
    .PARAMETER ServerName
    The target SQL Server
 
    .PARAMETER Alias
    The alias to be created
 
    .PARAMETER Protocol
    The protocol for the connection, either TCPIP or NetBIOS. Defaults to TCPIP.
 
    .PARAMETER EnableException
    By default, when something goes wrong we try to catch it, interpret it and give you a friendly warning message.
    This avoids overwhelming you with "sea of red" exceptions, but is inconvenient because it basically disables advanced scripting.
    Using this switch turns this "nice by default" feature off and enables you to catch exceptions with your own try/catch.
 
    .NOTES
    Tags: Alias
 
    Website: https://dbatools.io
    Copyright: (C) Chrissy LeMaire, clemaire@gmail.com
    License: MIT https://opensource.org/licenses/MIT
 
    .LINK
    https://dbatools.io/New-DbaClientAlias
 
    .EXAMPLE
    New-DbaClientAlias -ServerName sqlcluster\sharepoint -Alias sp
    Creates a new TCP alias on the local workstation called sp, which points sqlcluster\sharepoint
 
 
    .EXAMPLE
    New-DbaClientAlias -ServerName 'sqlcluster,14443' -Alias spinstance
    Creates a new TCP alias on the local workstation called spinstance, which points to sqlcluster, port 14443.
 
    .EXAMPLE
    New-DbaClientAlias -ServerName sqlcluster\sharepoint -Alias sp -Protocol NamedPipes
    Creates a new NamedPipes alias on the local workstation called sp, which points sqlcluster\sharepoint
 
#>

    [CmdletBinding()]
    Param (
        [DbaInstanceParameter[]]$ComputerName = $env:COMPUTERNAME,
        [PSCredential]$Credential,
        [parameter(Mandatory, ValueFromPipeline)]
        [DbaInstanceParameter[]]$ServerName,
        [parameter(Mandatory)]
        [string]$Alias,
        [ValidateSet("TCPIP", "NamedPipes")]
        [string]$Protocol = "TCPIP",
        [switch][Alias('Silent')]$EnableException
    )

    begin {
        # This is a script block so cannot use messaging system
        $scriptblock = {
            $basekeys = "HKLM:\SOFTWARE\WOW6432Node\Microsoft\MSSQLServer", "HKLM:\SOFTWARE\Microsoft\MSSQLServer"
            $ServerName = $args[0]
            $Alias = $args[1]
            $serverstring = $args[2]

            if ($env:PROCESSOR_ARCHITECTURE -like "*64*") { $64bit = $true }

            foreach ($basekey in $basekeys) {
                if ($64bit -ne $true -and $basekey -like "*WOW64*") { continue }

                if ((Test-Path $basekey) -eq $false) {
                    throw "Base key ($basekey) does not exist. Quitting."
                }

                $client = "$basekey\Client"

                if ((Test-Path $client) -eq $false) {
                    # "Creating $client key"
                    $null = New-Item -Path $client -Force
                }

                $connect = "$client\ConnectTo"

                if ((Test-Path $connect) -eq $false) {
                    # "Creating $connect key"
                    $null = New-Item -Path $connect -Force
                }

                if ($basekey -like "*WOW64*") {
                    $architecture = "32-bit"
                }
                else {
                    $architecture = "64-bit"
                }

                # Write-Verbose "Creating/updating alias for $ComputerName for $architecture"
                $null = New-ItemProperty -Path $connect -Name $Alias -Value $serverstring -PropertyType String -Force
            }
        }
    }

    process {
        if ($protocol -eq "TCPIP") {
            $serverstring = "DBMSSOCN,$ServerName"
        }
        else {
            $serverstring = "DBNMPNTW,\\$ServerName\pipe\sql\query"
        }

        foreach ($computer in $ComputerName.ComputerName) {

            $null = Test-ElevationRequirement -ComputerName $computer -Continue

            if ($PScmdlet.ShouldProcess($computer, "Adding $alias")) {
                try {
                    Invoke-Command2 -ComputerName $computer -Credential $Credential -ScriptBlock $scriptblock -ErrorAction Stop -ArgumentList $ServerName, $Alias, $serverstring
                }
                catch {
                    Stop-Function -Message "Failure" -ErrorRecord $_ -Target $computer -Continue
                }
            }
        }

        Get-DbaClientAlias -ComputerName $computer -Credential $Credential | Where-Object AliasName -eq $Alias
    }
}