>I am using a typed dataset and SqlDataAdapter to update data. How do I insert NULL value in the DataTime field? I tried DBNull.value and a few other things but none works.<

Unfortunately, at least with SQL Server, sending a NULL to the back-end just doesn't work ... with any data type, not just datetime.

The workaround that we use it just not to send NULLs to the backend ... we use Stored Procs for all our DataAccess ... the parameters in the SP default to NULL, so since we don't set a parameter for those columns in the DataSet that contain DBNull.value, the parameter will default to NULL in the SP and consequently a NULL value will be entered into the table that way. I don't know if that helps you much, but you're going to have to look for alternative ways to handle this anyway.

~~Bonnie