asp.net - Null value in SQL Server 2005 table -

i'm using table log has 3 columns:

• login nvarchar(50)
• date int
• logout nvarchar(50)

now if don't enter value logout column, null should stored. me stored " ".

i have given table definition in screenshot 1 , table data in screenshot 2.

may in insert query using insert log (login, date, logout) values(...) , "" value logout field. check insert statement , verify not making mistake.