Convert SQL with Inner AND Outer Join to L2S

I need to convert the below Sproc to a Linq query. At the very bottom is what I have so far. For reference the fields behind the "splat"(not my sproc) are

ImmunizationID int, HAReviewID int, ImmunizationMaintID int, ImmunizationOther varchar(50), ImmunizationDate smalldatetime, ImmunizationReasonID int

The first two are PK and FK, respectively. The other two ints are linke to the Maint Table where there description is stored. That is what I am stuck on, the INNER JOIN AND the LEFT OUTER JOIN

Thanks,

SELECT tblHAReviewImmunizations.*, 
       tblMaintItem.ItemDescription, 
       tblMaintItem2.ItemDescription as Reason
FROM 
       dbo.tblHAReviewImmunizations 
       INNER JOIN dbo.tblMaintItem 
            ON dbo.tblHAReviewImmunizations.ImmunizationMaintID =
                dbo.tblMaintItem.ItemID 
        LEFT OUTER JOIN dbo.tblMaintItem as tblMaintItem2 
            ON dbo.tblHAReviewImmunizations.ImmunizationReasonID =
                tblMaintItem2.ItemID 
WHERE
       HAReviewID = @haReviewID

My attempt so far -->

public static DataTable GetImmunizations(int haReviewID)
{
    using (var context = McpDataContext.Create())
    {
        var currentImmunizations =
            from haReviewImmunization in context.tblHAReviewImmunizations
            where haReviewImmunization.HAReviewID == haReviewID
            join maintItem in context.tblMaintItems
                on haReviewImmunization.ImmunizationReasonID 
                equals maintItem.ItemID into g
            from maintItem in g.DefaultIfEmpty() 
            let Immunization = GetImmunizationNameByID(
                haReviewImmunization.ImmunizationMaintID)
            select new
            {
                haReviewImmunization.ImmunizationDate,
                haReviewImmunization.ImmunizationOther,
                Immunization,
                Reason = 开发者_开发问答maintItem == null ? " " : maintItem.ItemDescription
            };

        return currentImmunizations.CopyLinqToDataTable();
    }
}

private static string GetImmunizationNameByID(int? immunizationID)
{
    using (var context = McpDataContext.Create())
    {
        var domainName =
            from maintItem in context.tblMaintItems
            where maintItem.ItemID == immunizationID
            select maintItem.ItemDescription;

        return domainName.SingleOrDefault();
    }
}

public static DataTable GetImmunizations(int haReviewID)
{
    using (var context = McpDataContext.Create())
    {
        var currentImmunizations =
            from haReviewImmunization in context.tblHAReviewImmunizations
            where haReviewImmunization.HAReviewID == haReviewID

            join maintItem in context.tblMaintItems
            on haReviewImmunization.ImmunizationMaintID 
            equals maintItem.ItemID

            join maintItem2 in context.tblMaintItems
            on haReviewImmunization.ImmunizationReasonID 
            equals maintItem2.ItemID into g
            from maintItem3 in g.DefaultIfEmpty()

            select new
            {
                haReviewImmunization.ImmunizationDate,
                haReviewImmunization.ImmunizationOther,
                maintItem.ItemDescription,
                Reason = maintItem3 == null ? " " : maintItem3.ItemDescription
            };

        return currentImmunizations.CopyLinqToDataTable();
    }
}