Database

SELECT  [Guid] ,
        UserGuid ,
        ReferenceGuid ,
        ReferenceID ,
        [Event] ,
        Comments ,
        [Time] ,
        IPAddress
FROM EventLogs AS elog
INNER JOIN (
    SELECT [Guid]
    FROM EventLogs elog1
    INNER JOIN (
        SELECT [Event], MAX([Time]) AS MTime
        FROM EventLogs
        GROUP BY [Event] ) AS t ON elog1.[Event] = t.[Event] AND elog1.[Time] = t.MTime
) AS elog3 ON elog.[Guid] = elog3.[Guid]

SELECT  [Guid] ,
        UserGuid ,
        ReferenceGuid ,
        ReferenceID ,
        [Event] ,
        Comments ,
        [Time] ,
        IPAddress
FROM     EventLogs
WHERE   ( [Guid] = ( SELECT TOP ( 1 )
                            [Guid]
                   FROM     EventLogs AS elog
                   WHERE    ( ReferenceGuid = EventLogs.ReferenceGuid AND Event=EventLogs.Event)
                   ORDER BY Time DESC
                 ) )

with cte as (
    SELECT  [Guid] ,
            UserGuid ,
            ReferenceGuid ,
            ReferenceID ,
            [Event] ,
            Comments ,
            [Time] ,
            IPAddress,
            rn = ROW_NUMBER() OVER (Partition By Event Order By Time Desc)
    FROM     EventLogs
)
select * from cte where rn = 1

protected void Calendar1_DayRender(object sender, DayRenderEventArgs e)
{
    DateTime FromDate =Convert.ToDateTime(ddlFrom.SelectedValue);
    DateTime ToDate =Convert.ToDateTime(ddlTo.SelectedValue);
 
   if(e.Day.Date >= FromDate && e.Day.Date <= ToDate )
   {
	e.Cell.BackColor = System.Drawing.Color.Red;
   }
}