Explain DataAdapter Object

It populates dataset from data source. It contains a reference to the connection object and opens and closes the connection automatically when reading from or writing to the database.

Example:
SqlDataAdapter daEmp = new SqlDataAdapter( "select EmpID, EmpName, Salary from Employees", conn);

Fill Method
It is used to populate dataset.
example: daEmp.Fill(dsEmp,"Employee");

Update Method
It is used to update database.
example: daEmp.Update(dsEmp,"Employee");

More about DataAdapter
DataAdapter object is like a bridge that links the database and a Connection object with the ADO.NET-managed DataSet object through its SELECT and action query Commands. It specifies what data to move into and out of the DataSet. Often, this takes the form of references to SQL statements or stored procedures that are invoked to read or write to a database.