functions/Get-DbaAgentJobCategory.ps1

function Get-DbaAgentJobCategory {
    <#
        .SYNOPSIS
            Get-DbaAgentJobCategory retrieves the job categories.
 
        .DESCRIPTION
            Get-DbaAgentJobCategory makes it possible to retrieve the job categories.
 
        .PARAMETER SqlInstance
             SQL Server name or SMO object representing the SQL Server to connect to. This can be a collection and receive pipeline input to allow the function to be executed against multiple SQL Server instances.
 
        .PARAMETER SqlCredential
            Login to the target instance using alternative credentials. Windows and SQL Authentication supported. Accepts credential objects (Get-Credential)
 
        .PARAMETER Category
            The name of the category to filter out. If no category is used all catgories will be returned.
 
        .PARAMETER CategoryType
            The type of category. This can be "LocalJob", "MultiServerJob" or "None".
            If no category is used all catgories types will be returned.
 
        .PARAMETER Force
            The force parameter will ignore some errors in the parameters and assume defaults.
 
        .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: Agent, Job, JobCategory
            Author: Sander Stad (@sqlstad, sqlstad.nl)
 
            Website: https://dbatools.io
            Copyright: (C) Chrissy LeMaire, clemaire@gmail.com
            License: MIT https://opensource.org/licenses/MIT
 
        .LINK
            https://dbatools.io/Get-DbaAgentJobCategory
 
        .EXAMPLE
            Get-DbaAgentJobCategory -SqlInstance sql1
 
            Return all the job categories.
 
        .EXAMPLE
            Get-DbaAgentJobCategory -SqlInstance sql1 -Category 'Log Shipping'
 
            Return all the job categories that have the name 'Log Shipping'.
 
        .EXAMPLE
            Get-DbaAgentJobCategory -SqlInstance sstad-pc -CategoryType MultiServerJob
 
            Return all the job categories that have a type MultiServerJob.
    #>

    [CmdletBinding(DefaultParameterSetName = "Default")]
    param (
        [parameter(Mandatory, ValueFromPipeline)]
        [Alias("ServerInstance", "SqlServer")]
        [DbaInstance[]]$SqlInstance,
        [Alias("Credential")]
        [PSCredential]$SqlCredential,
        [ValidateNotNullOrEmpty()]
        [string[]]$Category,
        [ValidateSet("LocalJob", "MultiServerJob", "None")]
        [string]$CategoryType,
        [switch]$Force,
        [Alias('Silent')]
        [switch]$EnableException
    )

    process {

        foreach ($instance in $SqlInstance) {
            Write-Message -Level Verbose -Message "Connecting to $instance."
            try {
                $server = Connect-SqlInstance -SqlInstance $instance -SqlCredential $SqlCredential
            }
            catch {
                Stop-Function -Message "Failure" -Category ConnectionError -ErrorRecord $_ -Target $instance -Continue
            }

            # get all the job categories
            $jobCategories = $server.JobServer.JobCategories |
                Where-Object {
                ($_.Name -in $Category -or !$Category) -and
                ($_.CategoryType -in $CategoryType -or !$CategoryType)
            }

            # Set the default output
            $defaults = 'ComputerName', 'InstanceName', 'SqlInstance', 'Name', 'ID', 'CategoryType', 'JobCount'

            # Loop through each of the categories
            try {
                foreach ($cat in $jobCategories) {

                    # Get the jobs associated with the category
                    $jobCount = ($server.JobServer.Jobs | Where-Object {$_.CategoryID -eq $cat.ID}).Count

                    # Add new properties to the category object
                    Add-Member -Force -InputObject $cat -MemberType NoteProperty -Name ComputerName -value $server.ComputerName
                    Add-Member -Force -InputObject $cat -MemberType NoteProperty -Name InstanceName -value $server.ServiceName
                    Add-Member -Force -InputObject $cat -MemberType NoteProperty -Name SqlInstance -value $server.DomainInstanceName
                    Add-Member -Force -InputObject $cat -MemberType NoteProperty -Name JobCount -Value $jobCount

                    # Show the result
                    Select-DefaultView -InputObject $cat -Property $defaults
                }
            }
            catch {
                Stop-Function -ErrorRecord $_ -Target $instance -Message "Failure. Collection may have been modified" -Continue
            }

        } # for each instance

    } # end process

    end {
        if (Test-FunctionInterrupt) { return }
        Write-Message -Message "Finished retrieving job category." -Level Verbose
    }

}