Insert as "Null" Value to Destination Column Table When Flat File source having "Blank" value in SSIS 2005

Hi Team,

I am using ssis 2005,

i am porting data from text file to sql server Table (oledb destination), i have to insert Null Value to destination table Column, when Source having Blank Value.

if so doing in Derived Column, then what is the expression i have to Mention

i have a text file of data say

-------------------------------------

No,Name,Place

1,supreeth,tumkur

,Prashanth,Mandya

3,,Kollar

This should be inserted in my table like

No                  Name                       Place

==============================

1                   Supreeth                 Tumkur

Null              Prashanth                Mandya

3                 Null                           kollar

Please reply to this Above Question.

Thanks

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Supreeth