1. Introduction to ADO.NET Programming

2. ADO.NET Objects Data Set.NET Applications Data Reader Command Object Connection Object Managed Data Provider (OLEDB) Database Adapter

3. Connection with a Connection Object A connection object represents a unique session with a data source. Connection string: database, OLE DB provider, password, if any, security, etc. Use the Open/Close method to open/close a connection. Other functions: –Manage transaction: BeginTransaction(), Commit, rollBack.

4. Connection String Containing information about database, OLE DB provider, password, if any, security, etc. For Jet database: –="Provider=Microsoft.Jet.OLEDB.4.0;Data Source = c:\sales2k.mdb"

5. Data Link Properties (Under the Advanced Tab of the Connection Dialog Window) Access permissions –Read—Read only. –ReadWrite—Read and write. –Share Deny None—Neither read nor write access can be denied to others. –Share Deny Read—Prevents others from opening in read mode. –Share Deny Write—Prevents others from opening in write mode. –Share Exclusive—Prevents others from opening in read/write mode. –Write—Write only.

6. Providers MSDASQL –Microsoft OLE DB Provider for ODBC Microsoft.Jet.OLEDB.3.51 Microsoft.Jet.OLEDB.4.0 MSDAORA – For Oracle SQLOLEDB – Microsoft SQL Server

7. Connection Object Example: –dim strConn as string ="Provider=Microsoft.Jet.OLEDB.4.0;Data Source = c:\sales2k.mdb" –dim objConn as new OledbConnection(strConn) –objConn.open() Basic Methods: –Open, Close –BeginTransaction

8. Command Object The command object allows us to execute a SQL statement. Properties: –CommandType: SQL or stored procedure –CommandText: SQL statement –Connection –Other properties: Parameters Basic Methods: –ExecuteReader: Creates a DataReader object that contains the results of the query. –ExecuteNonQuery: Change the data in a database without using a DataSet by executing SQL’s UPDATE, INSERT, or DELETE statements.

9. ExecuteReader Example dim strConn as string ="Provider=Microsoft.Jet.OLEDB.4.0;Data Source = c:\sales2k.mdb" dim objConn as new OledbConnection(strConn) dim strSQL as string = "select * from customer;" dim objComm as new OledbCommand(strSQL,objConn) dim Results as string objConn.open() dim objDataReader as oledbDataReader objDataReader=objComm.executeReader()

10. Import NameSpace The Imports statement must appear before all other declarations in a file and cannot appear inside a class or module declaration. –Imports System.Data.OleDb –Public Class Form1

11. DataReader Object It is read-only and forward-only cursor. Basic Methods: –Read: Reads the current record and advances the pointer to the next record. It returns False if no more record in the DataReader. –Close: Closes the dataReader.

12. Read Records in a DataReader dim Results as string do while objDataReader.Read()=true Results+=objDataReader("cid") + “ “ + objDataReader("Cname") + vbCrLF loop Textbox1.text=Results Note: objDataReader.Item(0) Note: objDataReader.Item(“cid”)

13. Add Items from a DataReader to a Listbox Dim strConn As String = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source = c:\sales2k.mdb" Dim objConn As New OleDbConnection(strConn) Dim strSQL As String = "select cname from customer;" Dim objComm As New OleDbCommand(strSQL, objConn) objConn.Open() Dim objDataReader As OleDbDataReader objDataReader = objComm.ExecuteReader() Do While objDataReader.Read() = True LISTBOX1.Items.Add(objDataReader("cname")) Loop Note1: Listbox is not bound. 2. SelectedItem Note2: With the data binding you cannot issue the Add method.

14. Use a DataReader to Retrieve Summaries Dim sfCount, laCount, aCount, bCount, cCOunt As Integer objConn.Open() Dim objDataReader As OleDbDataReader objDataReader = objComm.ExecuteReader() Do While objDataReader.Read() = True If objDataReader("city") = "sf" Then sfCount += 1 ElseIf objDataReader("city") = "la" Then laCount += 1 End If If objDataReader("rating") = "a" Then aCount += 1 ElseIf objDataReader("rating") = "b" Then bCount += 1 Else cCOunt += 1 End If Loop TextBox1.Text = sfCount.ToString TextBox2.Text = laCount.ToString TextBox3.Text = aCount.ToString TextBox4.Text = bCount.ToString TextBox5.Text = cCOunt.ToString

15. Use SQL to Retrieve Summaries Dim strConn As String = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source = c:\sales2k.mdb" Dim objConn As New OleDbConnection(strConn) Dim strSQL As String = "select count(cid) as custCount from customer;" Dim objComm As New OleDbCommand(strSQL, objConn) Dim Results As String objConn.Open() Dim objDataReader As OleDbDataReader objDataReader = objComm.ExecuteReader() If objDataReader.Read = True Then MessageBox.Show(objDataReader("custCount").ToString) End If

16. Testing for Null If objDataReader.Read = True Then If IsDBNull(objDataReader("custCount")) Then TextBox1.Text = 0 Else TextBox1.Text = objDataReader("custCount").ToString End If

17. To Reuse a DataReader objDataReader.Close() objDataReader = objComm.ExecuteReader()

18. Error Handling Try objConn.Open() Dim objDataReader As OleDbDataReader objDataReader = objComm.ExecuteReader() Do While objDataReader.Read() = True Results += objDataReader("cid") + " " + objDataReader("Cname") + vbCrLf Loop TextBox1.Text = Results objConn.Close() Catch except As System.Exception MessageBox.Show(except.Message) End Try

19. Possible Database Errors SQL syntax errors Database connection not open Violate database constraints Referential integrity Field data type and length Primary key constraint

20. ExecuteNonQuery Example dim strSQLUpd as string="Update customer set rating = ‘A’” strSQLUpd=strSQLUpd & " where cname='" & CnameList.selectedItem.text & "'“ Dim objCommUpd As New OleDbCommand(strSQLUpd, objConn) objCommUpd.ExecuteNonQuery() Note: How many records affected by this command? Messagebox.Show( objCommUpd.ExecuteNonQuery())

21. Demo Create a project that do the following tasks: –Use a DataReader to retrieve customer IDs and populate a listbox. –Select a new rating from radio buttons for the selected customer. –Update customer’s rating using the ExecuteNonQuery method of a Command object.

22. Declare OleDB objects and create listbox Imports System.Data.OleDb Public Class Form3 Inherits System.Windows.Forms.Form Dim strConn As String = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source = c:\sales2k.mdb" Dim objConn As New OleDbConnection(strConn) Dim strSQL As String = "select cid from customer;" Dim objComm As New OleDbCommand(strSQL, objConn) Private Sub Form3_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load objConn.Open() Dim objDataReader As OleDbDataReader objDataReader = objComm.ExecuteReader() Do While objDataReader.Read() = True ListBox1.Items.Add(objDataReader("cid")) Loop objConn.Close() End Sub

23. Update customer rating Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click objConn.Open() Dim newRating As String If RadioButton1.Checked = True Then newRating = "A" ElseIf RadioButton2.Checked Then newRating = "B" Else newRating = "C" End If Dim strSQLUpd As String = "Update customer set rating = '" & newRating & "'" strSQLUpd = strSQLUpd & " where cid='" & ListBox1.SelectedItem & "'" Dim objCommUpd As New OleDbCommand(strSQLUpd, objConn) objCommUpd.ExecuteNonQuery() objConn.Close() End Sub

24. Use Command Object’s ExecuteNonQuery to Insert A New Record 1.Create unbound text boxes to enter new record. 2.Add an Insert button with the following handler Dim strSQLInsert As String strSQLInsert = "Insert into Customer values ('" strSQLInsert = strSQLInsert & TextBox1.Text & "','" & TextBox2.Text & "','" strSQLInsert = strSQLInsert & TextBox3.Text & "','" & TextBox4.Text & "')" Dim objCommInsert As New OleDbCommand(strSQLInsert, objConn) objCommInsert.ExecuteNonQuery()

25. DataSet Object A DataSet object can hold several tables and relationships between tables. A DataSet is a set of disconnedted data. Data is extracted from the database and stored in the DataSet object. Updates to the DataSet must copy back to the database to make the changes permanent.

26. DataSet and Related Objects DataSet: Can contain multiple tables and relationships. DataTable object: Represents a table in the dataset. DataAdapter: This the object used to pass data between the database and the dataset. The Fill method copies the data into the dataset, and the Update method copies the updates back into the database. DataView: This represents a specific view of the DataTables held in the dataset.

27. DataSet and Related Objects DataView DataSet DataTable DataAdapter Connection Command

28. Structure of a Dataset Dataset Tables Data table Rows Data Row Columns Data Column Constraints Constraint Relations Data Relation

29. Reading Data into a Table dim strConn as string ="Provider=Microsoft.Jet.OLEDB.4.0;Data Source = c:\sales2k.mdb" dim objConn as new OledbConnection(strConn) dim strSQL as string = "select * from customer;" dim objDataSet as new Dataset() dim objAdapter as new OledbDataAdapter(strSQL, objConn) objAdapter.Fill(objDataSet, "Cust")

30. Binding a Table in a Dataset to a DataGrid Imports System.Data.OleDb Public Class Form4 Inherits System.Windows.Forms.Form Dim strConn As String = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source = c:\sales2k.mdb" Dim objConn As New OleDbConnection(strConn) Dim objDataSet As New DataSet() Private Sub Form4_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load Dim strSQL As String = "select * from customer;" Dim objAdapter As New OleDbDataAdapter(strSQL, objConn) objAdapter.Fill(objDataSet, "Cust") DataGrid1.DataSource = objDataSet DataGrid1.DataMember = "Cust" End Sub Note: Adapter’s Fill method is able to open the connection.

31. DataView Object A Better Way for Binding The DataView object exposes a complete table or a subset of the records from a table. Table’s DefaultView property: –Dim ObjDataView As New DataView() –ObjDataView.Table = objDataSet.Tables("Cust") –Or: ObjDataView = objDataSet.Tables("Cust").DefaultView DataView can be used as a DataSource in data binding.

32. Data Binding with DataView Object Dim strConn As String = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source = c:\sales2k.mdb" Dim objConn As New OleDbConnection(strConn) Dim objDataSet As New DataSet() Dim strSQL As String = "select * from customer;" Dim objAdapter As New OleDbDataAdapter(strSQL, objConn) objAdapter.Fill(objDataSet, "Cust") Dim ObjDataView As New DataView() ObjDataView = objDataSet.Tables("Cust").DefaultView DataGrid1.DataSource = ObjDataView

33. Selecting a Subset of Records with DataView’s RowFilter Property objDataView.RowFilter = criteria Note: The criteria can be a simple or complex condition.

34. DataView Example Dim ObjDataView As New DataView() Dim newRating As String If RadioButton1.Checked = True Then newRating = "A" ElseIf RadioButton2.Checked Then newRating = "B" Else newRating = "C" End If ObjDataView.Table = objDataSet.Tables("Cust") ObjDataView.RowFilter = "rating='" & newRating & "'" DataGrid1.Visible = True DataGrid1.DataSource = ObjDataView

35. Accessing Records in DataView Using DataView and DataRowView object’s Item property: objdataView = objDataSet.Tables("customer").DefaultView TextBox1.Text = objdataView.Item(rowIndex).Item(0) TextBox2.Text = objdataView.Item(rowIndex).Item(1) Move to the next record: rowIndex += 1 TextBox1.Text = objdataView.Item(rowIndex).Item(0) TextBox2.Text = objdataView.Item(rowIndex).Item(1) Note: To avoid out-of-bound, use the DataView’s Count property.

36. Defining an Adapter without A Command Object dim strConn as string ="Provider=Microsoft.Jet.OLEDB.4.0;Data Source = c:\sales2k.mdb" dim objConn as new OledbConnection(strConn) dim strSQL as string = "select * from customer;" dim objDataSet as new Dataset() dim objAdapter as new OledbDataAdapter(strSQL, objConn) objAdapter.Fill(objDataSet, "Cust")

37. Defining an Adapter with A Command Object dim strSQLCust as string = "select * from customer;" dim objComm as new OledbCommand() dim objAdapter as new OledbDataAdapter() dim objDataSet as new Dataset() objComm.Connection=objConn objComm.CommandType=COmmandType.Text objComm.CommandText=strSQLCust objAdapter.SelectCommand=objComm objConn.open() objAdapter.Fill(objDataSet, "Customer") Note:Adapter has SelectCommand, InsertCommand, DeleteCommand, UpdateCommand properties (Check Object Browser).

38. Creating Multiple Tables in A DataSet with One Adapter dim strSQLCust as string = "select * from customer;" dim strSQLOrder as string ="select * from orders;" dim objComm as new OledbCommand() dim objAdapter as new OledbDataAdapter() dim objDataSet as new Dataset() objComm.Connection=objConn objComm.CommandType=COmmandType.Text objComm.CommandText=strSQLCust objAdapter.SelectCommand=objComm objConn.open() objAdapter.Fill(objDataSet, "Customer") objComm.COmmandText=strSQLOrder objAdapter.Fill(objDataSet, "Orders")

39. Binding Multiple Tables to a DataGrid (Example 1) DataGrid1.DataSource = objDataSet

40. Binding Multiple Tables to a DataGrid (Example 2) Dim ObjDataView As New DataView() Dim TableName As String If RadioButton1.Checked = True Then ObjDataView = objDataSet.Tables("Customer").DefaultView Else ObjDataView = objDataSet.Tables("Orders").DefaultView End If DataGrid1.DataSource = ObjDataView

41. Adding Relationship to a Dataset The Dataset object has a Relations property. It is a collection of DataRelations. We can use a relationship to enforce the referential integrity. To define a DataRelation: –DataRelObj=DataRelation(RelationName, ParentTable Field, ChildTableField) Dim objRel As DataRelation objRel = New DataRelation("custOrder", objDataset.tables("customer").columns("cid"), objDataset.tables("orders").columns("cid")) Adding a relation to the dataset: –objDataSet.Relations.Add(objRel)

42. Creating a Hierarchical DataGrid Dim objRel As DataRelation objRel = New DataRelation("custOrder", objDataSet.Tables("customer").Columns("cid"), objDataSet.Tables("orders").Columns("cid")) objDataSet.Relations.Add(objRel) DataGrid1.DataSource = objDataSet.Tables("customer")

43. DataTable’s Rows Property This is a collection of all the records in a table, a collection of DataRow objects. DataRow object’s properties and methods.

44. Accessing a Record with Index objAdapter.Fill(objDataSet, "Customer") TextBox1.Text = objDataSet.Tables("Customer").Rows(rowIndex).Item(0) TextBox2.Text = objDataSet.Tables("Customer").Rows(rowIndex).Item(1)

45. Access Rows in a DataRow Collection dim objTable as DataTable = objDataset.Tables("Customer") dim objRow as DataRow For each objRow in objTable.Rows strResult=strResult+“ " & objRow("cid") & " " & objRow("cname") & vbCrLf Next

46. DataRow object’s GetChildRows Method Returns a collection of rows from another table that are related as child rows to this row.

47. Displaying Parent/Child Records in a Relation Define the relation. Specify the relation in the GetChildRows method of the DataRow object.

48. Imports System.Data.OleDb Public Class Form1 Inherits System.Windows.Forms.Form Dim strConn As String = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source = c:\sales2k.mdb" Dim objConn As New OledbConnection(strConn) Dim strSQLCust As String = "select * from customer;" Dim strSQLOrder As String = "select * from orders;" Dim objComm As New OledbCommand() Dim objAdapter As New OledbDataAdapter() Dim objDataSet As New DataSet() Dim objRel As DataRelation Dim strResult As String Dim rowIndex As Integer = 0 Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load objComm.Connection = objConn objComm.CommandType = CommandType.Text objComm.CommandText = strSQLCust objAdapter.SelectCommand = objComm objConn.Open() objAdapter.Fill(objDataSet, "Customer") objComm.CommandText = strSQLOrder objAdapter.Fill(objDataSet, "Orders") objRel = New DataRelation("custOrder", objDataSet.Tables("Customer").Columns("cid"), objDataSet.Tables("Orders").Columns("cid")) objDataSet.Relations.Add(objRel) Call showChild(rowIndex) End Sub

49. Private Sub showChild(ByVal RowIndex) TextBox1.Text = objDataSet.Tables("customer").Rows(RowIndex).Item("cid") TextBox2.Text = objDataSet.Tables("customer").Rows(RowIndex).Item("cname") Dim objOrderRel As DataRelation = objDataSet.Tables("customer").ChildRelations("custOrder") Dim strResult As String Dim objChildRow As DataRow For Each objChildRow In objDataSet.Tables("customer").Rows(RowIndex).GetChildRows(objOrderRel) strResult = strResult + objChildRow("oid") + " " + objChildRow("odate") + vbCrLf Next TextBox3.Text = strResult End Sub ****Note****: How to prevent EOF error? Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click rowIndex += 1 Call showChild(rowIndex) End Sub

50. Display Child Records in Grid This technique uses the fact that the DataView of a table can be used as a DataSource in binding a data grid. Assuming a Customer/Orders relationship, for each customer record: –Use Table object’s Clone method to create a temporary child table structure. –Use Table object’s ImportRow method to import child records to the clone table. –Use the clone table’s DefaultView to bind the DataGrid.

51. Dim objRow As DataRow Dim drFound As DataRow drFound = objDataSet.Tables("Customer").Rows("0") TextBox1.Text = drFound.Item("cid") TextBox2.Text = drFound.Item("cname") Dim childTable As DataTable childTable = objDataSet.Tables("orders").Clone For Each objRow In drFound.GetChildRows(objOrderRel) childTable.ImportRow(objRow) Next DataGrid1.DataSource = childTable.DefaultView

52. Binding a ListBox with Code Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load Dim strConn As String = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source = c:\sales2k.mdb" Dim objConn As New OleDbConnection(strConn) Dim strSQL As String = "select * from customer;" Dim objDataSet As New DataSet() Dim objAdapter As New OleDbDataAdapter(strSQL, objConn) objAdapter.Fill(objDataSet, "Customer") ListBox1.DataSource = objDataSet.Tables("Customer") ListBox1.DisplayMember = "CID" End Sub Private Sub ListBox1_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ListBox1.SelectedIndexChanged TextBox1.Text = ListBox1.SelectedItem.item("cname") End Sub Note: The FieldName for the DisplayMember is case-sensitive and should match the field name in the database.

53. Creating Parameter Queries 1. Specify the parameters in the SQL statement. –Dim strSQLOrder As String = "select * from orders where cid= ?;" 2. Add the parameters to the Command Object’s Parameters collection. –objComm.Parameters.Add("?cid", OleDbType.VarChar) 3. Assign the command to Adapter’s SelectCommand –objAdapter.SelectCommand=objComm 4. Set parameter’s value. –objAdapter.SelectCommand.Parameters("?cid").Value = ListBox1.SelectedItem.item("cid")

54. Parameter Query Example TextBox1.Text = ListBox1.SelectedItem.item("cname") Dim strConn As String = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source = c:\sales2k.mdb" Dim objConn As New OleDbConnection(strConn) objConn.Open() Dim strSQLOrder As String = "select * from orders where cid= ?;" Dim objComm As New OleDbCommand() Dim objAdapter As New OleDbDataAdapter() Dim objDataSet As New DataSet() objComm.Connection = objConn objComm.CommandType = CommandType.Text objComm.CommandText = strSQLOrder objComm.Parameters.Add("?cid", OleDbType.VarChar) objAdapter.SelectCommand = objComm objAdapter.SelectCommand.Parameters("?cid").Value = ListBox1.SelectedItem.item("cid") objAdapter.Fill(objDataSet, "Orders") DataGrid1.DataSource = objDataSet DataGrid1.DataMember = "orders"

55. Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load Dim strSQLOrder As String = "select * from customer where city= ?;" Dim objComm As New OleDbCommand() Dim objDataSet As New DataSet() objComm.Connection = objConn objComm.CommandType = CommandType.Text objComm.CommandText = strSQLOrder objComm.Parameters.Add("?city", OleDbType.VarChar) objAdapter.SelectCommand = objComm End Sub Private Sub RadioButton_CheckedChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles RadioButton1.CheckedChanged, RadioButton2.CheckedChanged, RadioButton3.CheckedChanged Dim ObjDataView As New DataView() Dim city As String If RadioButton1.Checked = True Then city = "sf" ElseIf RadioButton2.Checked Then city = "la" Else city = "new york" End If objAdapter.SelectCommand.Parameters("?city").Value = city objDataSet.Clear() objAdapter.Fill(objDataSet, "cust") DataGrid1.DataSource = objDataSet DataGrid1.DataMember = "cust" End Sub

56. Can we use child table’s view to display child records in a grid? –Use View’s Filter Dim ObjDataView As New DataView() ObjDataView.Table = objDataSet.Tables(“Orders") ObjDataView.RowFilter = “cid='" & ListBox1.SelectedItem.item("cid") & "'" DataGrid1.DataSource = ObjDataView

57. Multiple Forms: Where to import the oledb, and where to create the oledb objects Imports System.Data.OleDb Module Module1 Public strConn As String = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source = c:\sales2k.mdb" Public objConn As New OleDbConnection(strConn) Public strSQLCust As String = "select * from customer;" Public strSQLOrder As String = "select * from orders;" Public objComm As New OleDbCommand() Public objAdapter As New OleDbDataAdapter() Public objDataSet As New DataSet() Public objRel As DataRelation Public strResult As String Public rowIndex As Integer = 0 Public ObjDataView As New DataView() Public Sub main() objComm.Connection = objConn objComm.CommandType = CommandType.Text objComm.CommandText = strSQLCust objAdapter.SelectCommand = objComm objConn.Open() objAdapter.Fill(objDataSet, "Customer") objComm.CommandText = strSQLOrder objAdapter.Fill(objDataSet, "Orders") End Sub End Module

58. Using ToolBox/Data to Define Ado.Net Objects Connection: ToolBox/Data/OledbConnection –ConnectionString Command: ToolBox/Data/OledbCommand –Connection –CommandType –CommandText

59. Using DBMS Views Create views (queries) with DBMS Create commands to select records from views.