What is the use of Command objects?

Answer:

•ExecuteNonQuery
Executes the command defined in the CommandText property against the connection defined in the Connection property for a query that does not return any row (an UPDATE, DELETE, or INSERT). Returns an Integer indicating the number of rows affected by the query.

•ExecuteReader
Executes the command defined in the CommandText property against the connection defined in the Connection property. Returns a "reader" object that is connected to the resulting row set within the database, allowing the rows to be retrieved.

•ExecuteScalar
Executes the command defined in the CommandText property against the connection defined in the Connection property. Returns only a single value (effectively the first column of the first row of the resulting row set, any other returned columns and rows are discarded). It is fast and efficient when only a "singleton" value is required.