Mark Dixon 1 22 – Web applications: Writing data to Databases using ASP.Net

Mark Dixon 2 Questions: HTML in VB Are these correct (assume variables and fields exist)? f = f + r("Description") h = h + r(" Name") a = " " + a " " html = html + h = " " + h + " "   

Mark Dixon 3 Questions: Databases How many primary keys? How many foreign keys? 3 2

Mark Dixon 4 Session Aims & Objectives Aims –To introduce the fundamental ideas involved in using server-side code to write data to databases Objectives, by end of this week’s sessions, you should be able to: –create an ASP web page that allows the user to store data in database

Mark Dixon 5 Advice Don’t –put anything on desktop –Especially database

Mark Dixon 6 Example: Person v1 (Specification) User requirement: –Display people's details from database online –need 2 pages: smith jones dixon list of people jones sally person's details

Mark Dixon 7 Example: PeopleList.aspx v1 Sub Page_Load() Dim cs As String = "Driver={Microsoft Access Driver (*.mdb, *.accdb)};" + _ "Dbq=" + Server.MapPath("People.accdb") + ";" Dim cn As New OdbcConnection(cs) Dim cmd As OdbcCommand Dim r As OdbcDataReader Dim s As String cmd = New OdbcCommand("SELECT * FROM Person;", cn) cn.Open() r = cmd.ExecuteReader() s = "" Do While r.Read() s = s & r("Surname") & " " Loop cn.Close parData.InnerHtml = s End Sub

Mark Dixon 8 Example: PeopleList.aspx v2 Sub Page_Load() Dim cs As String = "Driver={Microsoft Access Driver (*.mdb, *.accdb)};" + _ "Dbq=" + Server.MapPath("People.accdb") + ";" Dim cn As New OdbcConnection(cs) Dim cmd As OdbcCommand Dim r As OdbcDataReader Dim s As String cmd = New OdbcCommand("SELECT * FROM Person;", cn) cn.Open() r = cmd.ExecuteReader() s = "" Do While r.Read() s = s & " " s = s & r("Surname") & " " Loop cn.Close parData.InnerHtml = s End Sub now links

Mark Dixon 9 Example: Person.aspx v2 Sub Page_Load() Dim cs As String = "Driver={Microsoft Access Driver (*.mdb, *.accdb)};" + _ "Dbq=" + Server.MapPath("People.accdb") + ";" Dim sql As String Dim cn As New OdbcConnection(cs) Dim cmd As OdbcCommand Dim r As OdbcDataReader Dim s As String sql = "SELECT * FROM Person WHERE id=" & Request.QueryString("id") cmd = New OdbcCommand(sql, cn) cn.Open() r = cmd.ExecuteReader() s = "" If r.Read() Then txtSurname.Value = r("Surname") End If cn.Close() End Sub Back to People List Surname: reads querystring (from previous page) displays data for selected record only

Mark Dixon 10 Example: Person v2 (Specification) User requirement: Display person’s details from database online –Change surname and save to database

Mark Dixon 11 Changing Data SQL –INSERT: inserts a new record INSERT INTO Person (Surname, Age) VALUES ('Smith', 21); –UPDATE: makes changes to specified record UPDATE Person Set Surname = 'Smith', Age = 21 WHERE id = 14; –DELETE: deletes specified record DELETE FROM Person WHERE id = 14

Mark Dixon 12 WARNING!! All changes permanent (no undo) WHERE clause is CRITICAL DELETE FROM Person; Will delete ALL records in table

Mark Dixon 13 Example: Person.aspx v3 (error) Dim cs As String = "Driver={Microsoft Access Driver (*.mdb, *.accdb)};" + _ "Dbq=" + Server.MapPath("People.accdb") + ";" Dim cn As New OdbcConnection(cs) Sub Page_Load() Dim sql As String Dim cmd As OdbcCommand Dim r As OdbcDataReader sql = "SELECT * FROM Person WHERE id=" & Request.QueryString("id") cmd = New OdbcCommand(sql, cn) cn.Open() r = cmd.ExecuteReader() If r.Read() Then txtSurname.Value = r("Surname") End If cn.Close() End Sub Sub btnSave_Click(s As Object, e As EventArgs) Handles btnSave.ServerClick Dim cmd As OdbcCommand Dim sql As String sql = "UPDATE [Person] " + _ " SET [Surname] = '" + txtSurname.Value + "'" + _ " WHERE id = " & Request.QueryString("id") & ";" cmd = New OdbcCommand(sql, cn) cn.Open() cmd.ExecuteNonQuery() cn.Close End Sub Save button executes SQL UPDATE PROBLEM: Page_Load re-reads old surname first

Mark Dixon 14 Example: Person.aspx v3b Dim cs As String = "Driver={Microsoft Access Driver (*.mdb, *.accdb)};" + _ "Dbq=" + Server.MapPath("People.accdb") + ";" Dim cn As New OdbcConnection(cs) Sub Page_LoadComplete(s As Object, e As EventArgs) Dim sql As String Dim cmd As OdbcCommand Dim r As OdbcDataReader sql = "SELECT * FROM Person WHERE id=" & Request.QueryString("id") cmd = New OdbcCommand(sql, cn) cn.Open() r = cmd.ExecuteReader() If r.Read() Then txtSurname.Value = r("Surname") End If cn.Close() End Sub Sub btnSave_Click(s As Object, e As EventArgs) Handles btnSave.ServerClick Dim cmd As OdbcCommand Dim sql As String sql = "UPDATE [Person] " + _ " SET [Surname] = '" + txtSurname.Value + "'" + _ " WHERE id = " & Request.QueryString("id") & ";" cmd = New OdbcCommand(sql, cn) cn.Open() cmd.ExecuteNonQuery() cn.Close End Sub Save button executes SQL UPDATE Fix: Use Page_LoadComplete

Mark Dixon 15 Example: Person.aspx v3c Dim cs As String = "Driver={Microsoft Access Driver (*.mdb, *.accdb)};" + _ "Dbq=" + Server.MapPath("People.accdb") + ";" Dim cn As New OdbcConnection(cs) Dim sql As String Sub Page_Load () cn.Open() End Sub Sub btnSave_Click (s As Object, e As EventArgs) Handles btnSave.ServerClick Dim cmd As OdbcCommand sql = "UPDATE [Person] " + _ " SET [Surname] = '" + txtSurname.Value + "'" + _ " WHERE id = " & Request.QueryString("id") & ";" cmd = New OdbcCommand(sql, cn) cmd.ExecuteNonQuery() End Sub Sub Page_LoadComplete (s As Object, e As EventArgs) Dim cmd As OdbcCommand Dim r As OdbcDataReader sql = "SELECT * FROM Person WHERE id=" & Request.QueryString("id") cmd = New OdbcCommand(sql, cn) r = cmd.ExecuteReader() If r.Read() Then txtSurname.Value = r("Surname") End If cn.Close() End Sub Page_Load: first Click events Page_LoadComplete: last

Mark Dixon 16 Database Permissions Generally –Read: works by default –Write: requires permissions Asp.Net pages run as user: –Visual Studio Logged in user –IIS ASP.Net Account NETWORKSERVICE IIS APPPOOL\DefaultAppPool

Mark Dixon 17 Database Permissions 1 Windows Explorer –Tools –Folder Options –View Tab Need to turn 'simple file sharing' off (as this disables the security tab in file properties)

Mark Dixon 18 Database Permissions 2 In order for ASP to write to a database –Need to give write access to Internet Guest Account for database file (People.mdb) Right-click on file in Windows Explorer (the following screens are for Windows XP)

Mark Dixon 19 Database Permissions 3 Click Security tab Click Add button

Mark Dixon 20 Database Permissions 4 Click Advanced button

Mark Dixon 21 Select Internet Guest Account IUSR_ … Click Find button Click user Click OK button Database Permissions 5

Mark Dixon 22 Database Permissions 6 Select Internet Guest Account Ensure write access is on Repeat for ASPNET account

Mark Dixon 23 Tutorial Exercise: Person Task 1: Get the Person (v1) example from the lecture working. Task 2: Modify your code, so that forename is displayed as well as surname (use a table). Task 3: Get the Person (v2 and v3) example from the lecture working. Task 3: Modify your code, so that a line of text is displayed confirming that data has been saved. Task 4: Modify your code, so that an add button is included, which allows a new record to be added. Task 5: Modify your code, so that a delete button is included, which allows the current record to be deleted.