What is the use of command objects in ADO.NET ? Dot Net Interview Questions

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They are used to connect connection object to Datareader or dataset.Following are the methods provided by command object :-

1. 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 rows (an UPDATE, DELETE or INSERT).Returns an Integer indicating the number of rows affected by the query.

2. 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 rowset within the database, allowing the rows to be retrieved.

3. 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 rowset). Any other returned columns and rows are discarded. Fast and efficient when only a "singleton" value is required.