Executes the query and returns the first column of the first row in the result set returned by the query. All other columns and rows are ignored.
Assembly: System.Data (in System.Data.dll)
Use the method to retrieve a single value (for example, an aggregate value) from a database. This requires less code than using the ExecuteReader method and performing the operations necessary to generate the single value using the data returned by a DbDataReader.
If the first column of the first row in the result set is not found, a null reference (Nothing in Visual Basic) is returned. If the value in the database is Nothing, the query returns DBNull.Value.