Convert PHP to .NET (for Datatables)

I am looking at the datatables example of parent/child, and it has the server side code written in PHP to pull the data.

 Can you please explain/convert this into VB.NET or C# so I can understand how to use it with my own data?

https://datatables.net/blog/2019-01-11

The sites.php and users.php appear to be under the "server-side php" topics.

Editor::inst( $db, 'sites' )
    ->fields(
        Field::inst( 'id' )->set( false ),
        Field::inst( 'name' )->validator( 'Validate::notEmpty' )
    )
    ->join(
        Mjoin::inst( 'users' )
            ->link( 'sites.id', 'users.site' )
            ->fields(
                Field::inst( 'id' )
            )
    )
    ->process( $_POST )
    ->json();

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if ( ! isset($_POST['site']) || ! is_numeric($_POST['site']) ) {
    echo json_encode( [ "data" => [] ] );
}
else {
    Editor::inst( $db, 'users' )
        ->field(
            Field::inst( 'users.first_name' ),
            Field::inst( 'users.last_name' ),
            Field::inst( 'users.phone' ),
            Field::inst( 'users.site' )
                ->options( 'sites', 'id', 'name' )
                ->validator( 'Validate::dbValues' ),
            Field::inst( 'sites.name' )
        )
        ->leftJoin( 'sites', 'sites.id', '=', 'users.site' )
        ->where( 'site', $_POST['site'] )
        ->process($_POST)
        ->json();
}

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Thanks!

Starr