I am just wondering if i want to return one varchar value should i use executeScalar() or executeNonQuery()? Thanks

Use ExecteScalar. ExecuteScalar is used when you just want one single value from one single row, as in:
SELECT Name FROM Users WHERE UniqueId = 42

ExecuteNonQuery is used for SQL statements that don't return any data (For example, INSERT, UPDATE, DELETE)

Oh okay ... thanks.

Thanks for the good advise.

This helped me with a problem with following error :
"Object reference not set to an instance of an object"

Chears Jan

You can use scalar for a delete or update, but obviously you won't get anything back, and that slows your app down a little bit. You can even use the full blown one that expects a table result set. You just don't want to. Things are flexible, though.

Minikay is right - hope I spelled that right!

ExecuteNonQuery = "Delete From SomeTable"
ExecuteScalar = "Select @@Identity"
Fill = "Select * From SomeTable"