Datatable VS dataview [duplicate]

Question

Hy , I really don't understand the difference between datatable and dataview since we can do :

   Dim dtb As New DataTable()
   Dim dtv As DataView = dtb.DefaultView

thanks in advance .

Answer 1

The Datatable is the unordered and unfiltered collection of DataRows extracted according to your query from your database.
The DataView (and you could have more than one) is a filtered and/or ordered view of the same data.

For example:

 using(SqlConnection cn = GetConnection())
 {
     cn.Open();
     SqlDataAdapter da = new SqlDataAdapter("SELECT * FROM Customers", cn);
     DataTable dt = new DataTable();
     da.Fill(dt);

     // At this point dt is filled with datarows extracted from the database in no particular order 
     // And the DefaultView presents the same record organization (or lack of), but...

     // Order on the default view by CustomerName
     dt.DefaultView.Sort = "CustomerName";
     foreach(DataRowView rv in dt.DefaultView)
          Console.WriteLine(rv["CustomerName"].ToString();

     // A new dataview with only a certain kind of customers ordered by name
     DataView dvSelectedCust = new DataView(dt, "CreditLevel = 1", "CustomerName", DataViewRowState.Unchanged);
     foreach(DataRowView rv in dvSelectedCust)
          Console.WriteLine(rv["CustomerName"],ToString();



 }

Of course creating and maintaining a DataView is an hit on performances and thus you have the choice to use it only when you really need it

Answer 2

There are lot of links available of internet related to this but for summary

DataView is customized view of a DataTable for sorting, filtering, searching, editing, and navigation. The DataView does not store data, but instead represents a connected view of its corresponding DataTable.

You can look into simple DataView Example in VB.