C# question

Datareader - Example of Connected Architecture. It will fetch the values directly from the database. The SQLConnection is open when we use Datareader.
-------------------------
Dataset - Example of Disconnected Architecture. All the changes/updated will not be reflected in the database.Changes will be done in database only with the connection is open. All changes will be made in local copy.
-----------------------------------

DataSet

We should use when the application is:

• Windows application
• Not too large data
• Returning multiple tables
• If, to be serialized
• Disconnected architecture
• To return from a WCF  service
• To send across layers
• Caching the data
• Do not need to open or close connection

Code snippet using dataset:
public DataSet GetRecord(Guid id, string procedureName) { DataSet resultSet = new DataSet(); SqlConnection connection = new SqlConnection(System.Configuration. ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString); SqlCommand command = new SqlCommand(procedureName, connection); command.CommandType = CommandType.StoredProcedure; command.Parameters["pID"].Value = id.ToString(); IDataAdapter adapter = new SqlDataAdapter(command); try { adapter.Fill(resultSet); } catch (Exception ex) { throw new PerformanceException(ex.Message, ex.InnerException); } return resultSet; }

DataReader

DataReader is a stream which is readonly and forward only. It fetches the record from databse and stores in the network buffer and gives whenever requests. DataReader releasese the records as query executes and do not wait for the entire query to execute. Therefore it is very fast as compare to the dataset. It releases only when read method is called.
Its usages:

• Web application
• Large data
• Returning multiple tables
• For Fast data access
• Needs explicitly closed
• Output parameter value will only available after close
• returns only a row after read

Code sample for DataReader:


public SqlDataReader GetRecord(Guid id, string procedureName)
{
SqlDataReader resultReader = null;
SqlConnection connection = new SqlConnection( ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString);
SqlCommand command = new SqlCommand(procedureName, connection);
command.CommandType = CommandType.StoredProcedure;
command.Parameters["pID"].Value = id.ToString();
try
{
connection.Open();
resultReader = command.ExecuteReader(CommandBehavior.CloseConnection);
}
catch (Exception ex)
{
if (resultReader != null || connection.State == ConnectionState.Open)
{
resultReader.Close();
connection.Close();
}
throw new PerformanceException(ex.Message, ex.InnerException);
}
return resultReader;
}

------------

Hope this helps