PowerShell function that will create and write custom event to windows eventlog area.

gistfile1.txt

Slightly modified function from: https://www.powershellbros.com/create-new-event-log-powershell-function/

function New-CustomEvent {
    [CmdletBinding()]
            
    # Parameters used in this function
    param
    ( 
        [Parameter(Mandatory = $false, HelpMessage="Provide eventlog name", ValueFromPipeline = $false)] $EventLog,
        [Parameter(Mandatory = $false, HelpMessage="Provide event source", ValueFromPipeline = $false)]  $Source,
        [Parameter(Mandatory = $false, HelpMessage="Provide event source", ValueFromPipeline = $false)]  $EventID,
        [Parameter(Mandatory = $true, HelpMessage="Provide event message", ValueFromPipeline = $true)] $Message,
        [Parameter(Mandatory = $false, HelpMessage="Select event instance", ValueFromPipeline = $false)]
        [ValidateSet("Information","Warning","Error")] $EventInstance = 'Error'
    ) 
 
    #Load the event source
    If ([System.Diagnostics.EventLog]::SourceExists($Source) -eq $false) {[System.Diagnostics.EventLog]::CreateEventSource($Source, $EventLog)}


    Switch ($EventInstance){
        {$_ -match 'Error'}       {$id = New-Object System.Diagnostics.EventInstance($EventID,1,1)} #ERROR EVENT
        {$_ -match 'Warning'}     {$id = New-Object System.Diagnostics.EventInstance($EventID,1,2)} #WARNING EVENT
        {$_ -match 'Information'} {$id = New-Object System.Diagnostics.EventInstance($EventID,1)}   #INFORMATION EVENT
    }

    $Object = New-Object System.Diagnostics.EventLog;
    $Object.Log       = $EventLog;
    $Object.Source    = $Source;

    $Object.WriteEvent($id, @($Message))
}