Using Visual Studio 2010 add connect string to Sharepoint 2010 to query database data

1. From VS2010 , add new sharepoint 2010 empty project as , and then add one new item "Virtual Web Part" name as "SQLWebPartTest"
2. In "SQLWebPartTest" ascx file , manual add codes for DetailsView and SqlDataSource .
-----------
＜asp:DetailsView ID="DetailsView1" runat="server"
DataSourceID="SqlDataSource1" EnableModelValidation="True"＞
＜/asp:DetailsView＞
＜asp:SqlDataSource ID="SqlDataSource1" runat="server"
ConnectionString="＜%$ ConnectionStrings:ChangebyYourConnectionString %＞"
SelectCommand="select * from ChangebyYourTable"＞
＜/asp:SqlDataSource＞

＜asp:DetailsView ID="DetailsView2" runat="server"
DataSourceID="SqlDataSource2" EnableModelValidation="True"＞
＜/asp:DetailsView＞
＜asp:SqlDataSource ID="SqlDataSource2" runat="server"
ConnectionString="＜%$ ConnectionStrings:ChangebyYourConnectionString2 %＞"
SelectCommand="select * from ChangebyYourTable"＞
＜/asp:SqlDataSource＞
--------------
3. In the project "Solution Explorer" , right click in "Feature1" to add one "Event Receiver" and name it as "Feature1.EventReceiver.cs"
--- In "Feature1.EventReceiver.cs"
#1 Add using
using System.Reflection;
using Microsoft.SharePoint.Administration;

#2 Add following code in "public class Feature1EventReceiver : SPFeatureReceiver"
private ModificationEntry[] entries =
｛
//Ensure there's a connectionStrings section.
new ModificationEntry(
"connectionStrings"
,"configuration"
,"＜connectionStrings/＞"
,SPWebConfigModification.SPWebConfigModificationType.EnsureChildNode
,true)
//Create the connectionstring.
,new ModificationEntry(
"add[@name='ChangebyYourConnectionString'][@connectionString='Data Source=192.168.0.1;Initial Catalog=ChangebyYourDB;User Id=ChangebyYourID;Password=ChangebyYourPWD']"
,"configuration/connectionStrings"
,"＜add name='ChangebyYourConnectionString' connectionString='Data Source=192.168.0.1;Initial Catalog=ChangebyYourDB;User Id=ChangebyYourID;Password=ChangebyYourPWD'/＞"
,SPWebConfigModification.SPWebConfigModificationType.EnsureChildNode
,false)
,new ModificationEntry(
"add[@name='ChangebyYourConnectionString2'][@connectionString='Data Source=192.168.0.100;Initial Catalog=AdventureWorks;User Id=ChangebyYourID;Password=ChangebyYourPWD']"
,"configuration/connectionStrings"
,"＜add name='ChangebyYourConnectionString2' connectionString='Data Source=192.168.2.100;Initial Catalog=AdventureWorks;User Id=ChangebyYourID;Password=ChangebyYourPWD'/＞"
,SPWebConfigModification.SPWebConfigModificationType.EnsureChildNode
,false)
｝;

public override void FeatureActivated(SPFeatureReceiverProperties properties)
｛
//Get a reference to the web application and then remove entries for the blorum.
SPSite site = properties.Feature.Parent as SPSite;
SPWebApplication webApplication = site.WebApplication;

site.RootWeb.Title = "Set from activating code at " + DateTime.Now.ToString();
site.RootWeb.Update();

foreach (ModificationEntry entry in entries)
｛
webApplication.WebConfigModifications.Add(CreateModification(entry));
｝

webApplication.WebService.WebConfigModifications.Clear();
webApplication.WebService.ApplyWebConfigModifications();


｝

public override void FeatureDeactivating(SPFeatureReceiverProperties properties)
｛
SPSite site = properties.Feature.Parent as SPSite;
SPWebApplication webApplication = site.WebApplication;

site.RootWeb.Title = "Set from deactivating code at " + DateTime.Now.ToString();
site.RootWeb.Update();

foreach (ModificationEntry entry in entries)
｛
if (!entry.CreateOnly)
webApplication.WebConfigModifications.Remove(CreateModification(entry));
｝

webApplication.WebService.ApplyWebConfigModifications();
｝


private SPWebConfigModification CreateModification(ModificationEntry entry)
｛
SPWebConfigModification modification = new SPWebConfigModification(entry.Name, entry.XPath);
modification.Owner = Assembly.GetExecutingAssembly().FullName;
modification.Sequence = 0;
modification.Type = entry.ModificationType;
modification.Value = entry.Value;

return modification;
｝

private struct ModificationEntry
｛
public string Name;
public string XPath;
public string Value;
public SPWebConfigModification.SPWebConfigModificationType ModificationType;
public bool CreateOnly;

public ModificationEntry(string name, string xPath, string value,
SPWebConfigModification.SPWebConfigModificationType modificationType, bool createOnly)
｛
Name = name;
XPath = xPath;
Value = value;
ModificationType = modificationType;
CreateOnly = createOnly;
｝
｝
4. Press F5 in VS2010 to open Sharepoint site , and insert add webpart from "custom" location.