internal/Get-SqlDefaultPaths.ps1

Function Get-SqlDefaultPaths
{
<#
.SYNOPSIS
Internal function. Returns the default data and log paths for SQL Server. Needed because SMO's server.defaultpath is sometimes null.
#>

    [CmdletBinding()]
    param (
        [Parameter(Mandatory = $true)]
        [ValidateNotNullOrEmpty()]
        [Alias("ServerInstance", "SqlInstance")]
        [object]$SqlServer,
        [Parameter(Mandatory = $true)]
        [ValidateNotNullOrEmpty()]
        [string]$filetype,
        [System.Management.Automation.PSCredential]$SqlCredential
    )
    
    $server = Connect-SqlServer -SqlServer $SqlServer -SqlCredential $SqlCredential
    
    switch ($filetype) { "mdf" { $filetype = "data" } "ldf" { $filetype = "log" } }
    
    if ($filetype -eq "log")
    {
        # First attempt
        $filepath = $server.DefaultLog
        # Second attempt
        if ($filepath.Length -eq 0) { $filepath = $server.Information.MasterDbLogPath }
        # Third attempt
        if ($filepath.Length -eq 0)
        {
            $sql = "select SERVERPROPERTY('InstanceDefaultLogPath') as physical_name"
            $filepath = $server.ConnectionContext.ExecuteScalar($sql)
        }
    }
    else
    {
        # First attempt
        $filepath = $server.DefaultFile
        # Second attempt
        if ($filepath.Length -eq 0) { $filepath = $server.Information.MasterDbPath }
        # Third attempt
        if ($filepath.Length -eq 0)
        {
            $sql = "select SERVERPROPERTY('InstanceDefaultDataPath') as physical_name"
            $filepath = $server.ConnectionContext.ExecuteScalar($sql)
        }
    }
    
    if ($filepath.Length -eq 0) { throw "Cannot determine the required directory path" }
    $filepath = $filepath.TrimEnd("\")
    return $filepath
}