Comparison of dataAdapter .Fill and .Update

Question

I\'ve been reading through the MSDN resources and several forums and still don\'t understand what\'s the difference between those two dataAdapter.Fill() and

Answer 1

For short the definition.

DataAdapter.Fill() stands for SELECT query statement to database from the Server.

// 1
// Open connection
using (SqlConnection c = new SqlConnection(
        Properties.Settings.Default.DataConnectionString))
{
   c.Open();
   // 2
   // Create new DataAdapter
   using (SqlDataAdapter a = new SqlDataAdapter("SELECT * FROM EmployeeIDs", c))
     {
      // 3
      // Use DataAdapter to fill DataTable
         DataTable t = new DataTable();
         a.Fill(t);

         // 4
         // Render data onto the screen
         // dataGridView1.DataSource = t; // <-- From your designer
    }
  }

DataAdapter.Update() stands for Update, Insert and Delete query statement to database from the Server.

public DataSet CreateCmdsAndUpdate(DataSet myDataSet,string myConnection,string mySelectQuery,string myTableName) 
{
    OleDbConnection myConn = new OleDbConnection(myConnection);
    OleDbDataAdapter myDataAdapter = new OleDbDataAdapter();
    myDataAdapter.SelectCommand = new OleDbCommand(mySelectQuery, myConn);
    OleDbCommandBuilder custCB = new OleDbCommandBuilder(myDataAdapter);

    myConn.Open();

    DataSet custDS = new DataSet();
    myDataAdapter.Fill(custDS);

    //code to modify data in dataset here

    //Without the OleDbCommandBuilder this line would fail
    myDataAdapter.Update(custDS);

    myConn.Close();

    return custDS;
 }

Reference:
C# SqlDataAdapter
DataAdapter.Update Method