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ADO.NET Series - Populating DataSet
In previous articles of the series we saw how to SELECT data from database into a DataReader and iterate through it. As we saw the DataReader is a connected, read-only and forward only cursor. In this article we will see how to populate DataSet from database data.
What is DataSet
DataSet is an in-memory replica of database. Just like database, a DataSet can contain tables, relations and constraints. In the simplest form it is used to hold data from various SELECT queries. The data is stored in DataSet in the form of one or more DataTables.
//This sample shows how to populate dataset
static void Main(string args)
//declare connection,datadapter and dataset
//set selectcommand property
("select * from employees",cnn);
//populate the dataset
- We first imported System.Data and System.Data.SqlClient namespaces.
- Inside the Main method we create connection, command objects as usual.
- Next, we also create an instance of DataAdapter class. The DataAdapter is a bridge between your database and DataSet.
- We then create an instance of DataSet class.
- The DataAdapter class has a property called SelectCommand that is responsible for fetching the data.
- This property needs to set to valid command object that actually has the SELECT command or stored procedure.
- That is why we set SelectCommand property to the SqlCommand instance we created.
- We then call the Fill() method of the DataAdapter that actually populates the DataSet with the records.
- The second parameter of the Fill() method represents the DataTable name (employees in our case) that gets created after the filling operation.
- To check whether data really got populated in the DataSet or not we simply output various field values to the console. The iteration is done using Rows collection of the DataTable.
In this article we saw how to populate DataSet with data from database table. DataSet is an in-memory replica of database which can contain one or more result sets of data in the form of DataTables.
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