functions/Get-DbaAgentAlert.ps1

function Get-DbaAgentAlert {
    <#
        .SYNOPSIS
            Returns all SQL Agent alerts on a SQL Server Agent.
 
        .DESCRIPTION
            This function returns SQL Agent alerts.
 
        .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)
 
        .NOTES
            Tags: Agent, SMO
            Author: Klaas Vandenberghe (@PowerDBAKlaas)
 
            Website: https://dbatools.io
            Copyright (c) 2018 by dbatools, licensed under MIT
            License: MIT https://opensource.org/licenses/MIT
 
        .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.
 
        .LINK
            https://dbatools.io/Get-DbaAgentAlert
 
        .EXAMPLE
            PS C:\> Get-DbaAgentAlert -SqlInstance ServerA,ServerB\instanceB
 
            Returns all SQL Agent alerts on serverA and serverB\instanceB
 
        .EXAMPLE
            PS C:\> 'serverA','serverB\instanceB' | Get-DbaAgentAlert
 
            Returns all SQL Agent alerts on serverA and serverB\instanceB
    #>

    [CmdletBinding()]
    param (
        [parameter(Position = 0, Mandatory, ValueFromPipeline)]
        [Alias("ServerInstance", "Instance", "SqlServer")]
        [DbaInstanceParameter[]]$SqlInstance,
        [PSCredential]
        $SqlCredential,
        [Alias('Silent')]
        [switch]$EnableException
    )

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

            Write-Message -Level Verbose -Message "Getting Edition from $server"
            Write-Message -Level Verbose -Message "$server is a $($server.Edition)"

            if ($server.Edition -like 'Express*') {
                Stop-Function -Message "There is no SQL Agent on $server, it's a $($server.Edition)" -Continue
            }

            $defaults = "ComputerName", "SqlInstance", "InstanceName", "Name", "ID", "JobName", "AlertType", "CategoryName", "Severity", "IsEnabled", "DelayBetweenResponses", "LastRaised", "OccurrenceCount"

            $alerts = $server.Jobserver.Alerts

            foreach ($alert in $alerts) {
                $lastraised = [dbadatetime]$alert.LastOccurrenceDate

                Add-Member -Force -InputObject $alert -MemberType NoteProperty -Name ComputerName -value $server.ComputerName
                Add-Member -Force -InputObject $alert -MemberType NoteProperty -Name InstanceName -value $server.ServiceName
                Add-Member -Force -InputObject $alert -MemberType NoteProperty -Name SqlInstance -value $server.DomainInstanceName
                Add-Member -Force -InputObject $alert -MemberType NoteProperty Notifications -value $alert.EnumNotifications()
                Add-Member -Force -InputObject $alert -MemberType NoteProperty LastRaised -value $lastraised

                Select-DefaultView -InputObject $alert -Property $defaults
            }
        }
    }
}