ADO .NET (1) notes/Lecture Notes 3403 week 07...ADO .NET (ActiveX Data Objects) • ADO.NET is a...

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ADO .NET (1)

These slides are meant to be for teaching purposes only and only for the students that are registered in CSE3403 and should not be published as a

book or in any form of commercial product, unless written permission is obtained.

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ADO .NET (ActiveX Data Objects)

• ADO.NET is a component of .NET that allows access to relational databases from within C# (and other languages) programs.

• A database is – Integrated collection of data– Database management system (DBMS)

• Provides mechanisms for storing and organizing data in a way that is consistent with database’s format

• Allows storage and access to database without knowledge of internal representation

– Relational Databases most popular• Use Structured Query Language (SQL) to perform queries (search)

and manipulate data• Programming languages need an interface to interact with relational

databases

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Relational data bases overview

• Logical representation of data:– Date can be considered without concern for the

physical structure of data• Composed of tables

– Rows called records (or tuples)– Columns called fields (or attributes)– Primary key: field that contains unique data

• Each tuple can be identified by the value of primary key.

– New sets made from queries called result sets

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Example. A students data base in MS Access.

Table Student

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A table (Student table)

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Queries

• We can access and modify data stored in a relational database using a query language.

• The primary query language used nowadays is SQL (Structured Query Language).

• SQL allows – Extracting data from a database.– Modifying data in the database. – And other things.

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ADO .NET

• ADO .NET provides an API for accessing database systems from within programs written in one of the .NET languages (such as C#).

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ADO process and some related classes

• Establish connection to a desired DB– OleDbConnection

• Create a SQL query– OleDbCommand

• Send query to DB and retrieve data– OleDbAdapter

• Store retrieved data (in memory)– DataSet

• Display data on GUI– DataGrid.

• Work with individual values from retrieved data– DataTable, DataRow, DataColumn.

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How to connect to a database

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How to connect to a database

…

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How to connect to a database …

Navigate and find the desired DB

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How to connect to a database …/

Drag and drop this in your GUI … creates an OleDbConnection

that is capable to connecting to the DB as soon as you start

the program.

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Data menu from ToolBox has related buttons …

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Next … need to add an OleDbDataAdapter.

• The OleDbDataAdapter allows to create a query (and submit it to the DB).

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Adding an OleDbDataAdapter

As soon as the data adapter is dropped, the Configuration Wizard opens.

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Setting up a query

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Setting up a query …

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Setting up a query … select tables involved.

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Setting up a query …write your query

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Once the data adapter wizard is finished, its properties reflect the set query.

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Next … need to add a DataSet. • The data adapter retrieves the data and the dataSet captures the retrieved

data and holds it in memory. (after that we can display this data on a DataGrid).

Attempting to drop a DataSetin the designer view, it opens

the “Add Dataset” wizard.

Select “Untyped” dataset”.

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DataSet added.

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Next … we need to add a DataGrid.

• A DataGrid is used to display, in the GUI, the data that is held in a DataSet.

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Finally … we need to write the code to “connect” the DataAdapter to the DataSet and the DataSet to the

dataGrid.

Add code here.

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Writing the code ..

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Writing the code …/

“execute the query that is defined in oleDbDataAdapter1, and put the retrieved data

into dataSet1”. Have a reference name “someStorage” for this data.

“Take a data that is held in dataSet1 and put it in dataGrid1.”

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Running ..

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Another example …

Entire table

Projection on table

Dept

Join of two tables (Student and Enroll)

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Tables Student, Dept, Enroll

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Designer view

Use 3 adapters and 3 datasets.

The format of the data grid is set by the DataGrid properties.

Right-click …

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Adapter 1 properties

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Adapter 1 query builder

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The code

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The related codepublic Form1(){

InitializeComponent();

oleDbDataAdapter1.Fill( dataSet1, "Student");dataGrid1.SetDataBinding( dataSet1, "Student");

oleDbDataAdapter2.Fill( dataSet2, "Dept");dataGrid2.SetDataBinding( dataSet2, "Dept");

oleDbDataAdapter3.Fill( dataSet3, "res");dataGrid3.SetDataBinding( dataSet3,"res");

}

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ADO .NET (2)



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Another example (modify the DB)

The Course table retrieved.

Upon entering a course number (e.g., 778) and clicking the button, the course

(“New course”, 778, “Computer Sciences”) is added to the Course

table.

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.../

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The related code.

The button event

dataSet1 holds the Course table before the insertion.

dataSet2 holds the Course table after the insertion.

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The code …

public Form1()

{InitializeComponent();

oleDbDataAdapter1.Fill( dataSet1, "res");

dataGrid1.SetDataBinding( dataSet1, "res");

}

Retrieve and display the table before the

insertion.

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The code …/private void button1_Click(object sender, System.EventArgs e){

string theInsertSQL;theInsertSQL = "INSERT INTO Course (cname, cno, dname) "

+ " VALUES ( 'New Course' , "+ textBox1.Text + " , 'Computer Sciences' )";

oleDbDataAdapter1.InsertCommand.CommandText = theInsertSQL;

oleDbConnection1.Open();

oleDbDataAdapter1.InsertCommand.ExecuteNonQuery();

dataSet2.Clear(); // clear the accepting dataSet … just in case (no need here).

oleDbDataAdapter1.Fill( dataSet2, "res");dataGrid2.SetDataBinding( dataSet2, "res");

}

Load query results in dataSet and and display on

dataGrid.

Assemble query

Establish connection to DB

Execute query

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Extract individual values from a DataGrid

• Can extract individual values from a DataGrid(using classes DataTable, DataRow, DataColumn).

DataTable myTable = dataGrid1.DataSource;

private void PrintValues(DataTable myTable){

foreach( DataRow myRow in myTable.Rows){

foreach( DataColumn myCol in myTable.Columns){

Console.WriteLine(myRow[myCol]);

}

}

}

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ADO and XML

• Once the data is in the DataSet, it can be converted to XML. – The XML can be written to a file

• dataSet1.WriteXml( "Course.xml") or– Can be displayed in the GUI

• dataSet1.GetXml( )

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Example …

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XML file generated

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The design

Generates XML and writes it in file and also in TextBox

TextBox that displays XML

Retrieves Course table

Gets filled with Course table.

DataGrid

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using System;using System.Drawing;using System.Collections;using System.ComponentModel;using System.Windows.Forms;using System.Data;

namespace WindowsApplication2ADOXML{

/// <summary>/// Summary description for Form1./// </summary>public class Form1 : System.Windows.Forms.Form{

private System.Data.OleDb.OleDbConnection oleDbConnection1;private System.Data.OleDb.OleDbDataAdapter oleDbDataAdapter1;private System.Data.DataSet dataSet1;private System.Windows.Forms.DataGrid dataGrid1;private System.Data.OleDb.OleDbCommand oleDbSelectCommand1;private System.Data.OleDb.OleDbCommand oleDbInsertCommand1;private System.Windows.Forms.Button button1;private System.Windows.Forms.TextBox textBox1;/// <summary>/// Required designer variable./// </summary>private System.ComponentModel.Container components = null;

public Form1(){

//// Required for Windows Form Designer support//InitializeComponent();

//// TODO: Add any constructor code after InitializeComponent call//oleDbDataAdapter1.Fill( dataSet1, "res");dataGrid1.SetDataBinding( dataSet1, "res");

}

The code …

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…protected override void Dispose( bool disposing )

{

if( disposing )

{

if (components != null)

{

components.Dispose();

}

}

base.Dispose( disposing );

}

#region Windows Form Designer generated code

/// <summary>

/// Required method for Designer support - do not modify

/// the contents of this method with the code editor.

/// </summary>

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…private void InitializeComponent(){

this.oleDbConnection1 = new System.Data.OleDb.OleDbConnection();this.oleDbDataAdapter1 = new System.Data.OleDb.OleDbDataAdapter();this.oleDbInsertCommand1 = new System.Data.OleDb.OleDbCommand();this.oleDbSelectCommand1 = new System.Data.OleDb.OleDbCommand();this.dataSet1 = new System.Data.DataSet();this.dataGrid1 = new System.Windows.Forms.DataGrid();this.button1 = new System.Windows.Forms.Button();this.textBox1 = new System.Windows.Forms.TextBox();((System.ComponentModel.ISupportInitialize)(this.dataSet1)).BeginInit();

((System.ComponentModel.ISupportInitialize)(this.dataGrid1)).BeginInit();this.SuspendLayout();// // oleDbConnection1// this.oleDbConnection1.ConnectionString = @"Jet OLEDB:Global Partial Bulk

Ops=2;Jet OLEDB:Registry Path=;Jet OLEDB:Database Locking Mode=1;Data Source=""E:\4413 -- e-commerce course\__WINTER 2006\MySlides\_Slides _3 ADO NET slides\ADO .NET My code tests\MyStudentsDB.mdb"";Jet OLEDB:Engine Type=5;Provider=""Microsoft.Jet.OLEDB.4.0"";Jet OLEDB:System database=;Jet OLEDB:SFP=False;persist security info=False;Extended Properties=;Mode=Share Deny None;Jet OLEDB:Encrypt Database=False;Jet OLEDB:Create System Database=False;Jet OLEDB:Don't Copy Locale on Compact=False;Jet OLEDB:Compact Without Replica Repair=False;User ID=Admin;Jet OLEDB:Global Bulk Transactions=1";

// // oleDbDataAdapter1// this.oleDbDataAdapter1.InsertCommand = this.oleDbInsertCommand1;this.oleDbDataAdapter1.SelectCommand = this.oleDbSelectCommand1;this.oleDbDataAdapter1.TableMappings.AddRange(new

System.Data.Common.DataTableMapping[] {new System.Data.Common.DataTableMapping("Table", "Course", new

System.Data.Common.DataColumnMapping[] {

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…new System.Data.Common.DataColumnMapping("cname", "cname"),new System.Data.Common.DataColumnMapping("cno", "cno"),

new System.Data.Common.DataColumnMapping("dname", "dname")})});// // oleDbInsertCommand1//

this.oleDbInsertCommand1.CommandText = "INSERT INTO Course(cname, cno, dname) VALUES (?, ?, ?)";this.oleDbInsertCommand1.Connection = this.oleDbConnection1;this.oleDbInsertCommand1.Parameters.Add(new

System.Data.OleDb.OleDbParameter("cname", System.Data.OleDb.OleDbType.VarWChar, 255, "cname"));this.oleDbInsertCommand1.Parameters.Add(new

System.Data.OleDb.OleDbParameter("cno", System.Data.OleDb.OleDbType.Integer, 0, "cno"));this.oleDbInsertCommand1.Parameters.Add(new

System.Data.OleDb.OleDbParameter("dname", System.Data.OleDb.OleDbType.VarWChar, 255, "dname"));// // oleDbSelectCommand1// this.oleDbSelectCommand1.CommandText = "SELECT cname, cno, dname FROM Course";this.oleDbSelectCommand1.Connection = this.oleDbConnection1;// // dataSet1// this.dataSet1.DataSetName = "NewDataSet";this.dataSet1.Locale = new System.Globalization.CultureInfo("en-US");// // dataGrid1//

this.dataGrid1.AlternatingBackColor = System.Drawing.Color.WhiteSmoke;

this.dataGrid1.BackColor = System.Drawing.Color.Gainsboro;this.dataGrid1.BackgroundColor = System.Drawing.Color.DarkGray;this.dataGrid1.BorderStyle = System.Windows.Forms.BorderStyle.FixedSingle;this.dataGrid1.CaptionBackColor = System.Drawing.Color.DarkKhaki;this.dataGrid1.CaptionFont = new System.Drawing.Font("Tahoma", 8F,

System.Drawing.FontStyle.Bold);this.dataGrid1.CaptionForeColor = System.Drawing.Color.Black;this.dataGrid1.CaptionText = "Course";this.dataGrid1.DataMember = "";this.dataGrid1.FlatMode = true;this.dataGrid1.Font = new System.Drawing.Font("Times New Roman", 9F);this.dataGrid1.ForeColor = System.Drawing.Color.Black;this.dataGrid1.GridLineColor = System.Drawing.Color.Silver;this.dataGrid1.HeaderBackColor = System.Drawing.Color.Black;

this.dataGrid1.HeaderFont = new System.Drawing.Font("Tahoma", 8F, System.Drawing.FontStyle.Bold);

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…this.dataGrid1.HeaderForeColor = System.Drawing.Color.White;this.dataGrid1.LinkColor = System.Drawing.Color.DarkSlateBlue;this.dataGrid1.Location = new System.Drawing.Point(16, 24);this.dataGrid1.Name = "dataGrid1";this.dataGrid1.ParentRowsBackColor = System.Drawing.Color.LightGray;this.dataGrid1.ParentRowsForeColor = System.Drawing.Color.Black;this.dataGrid1.SelectionBackColor = System.Drawing.Color.Firebrick;this.dataGrid1.SelectionForeColor = System.Drawing.Color.White;this.dataGrid1.Size = new System.Drawing.Size(400, 128);this.dataGrid1.TabIndex = 0;// // button1this.button1.Font = new System.Drawing.Font("Microsoft Sans Serif", 10F,

System.Drawing.FontStyle.Bold, System.Drawing.GraphicsUnit.Point, ((System.Byte)(161)));this.button1.Location = new System.Drawing.Point(16, 168);this.button1.Name = "button1";this.button1.Size = new System.Drawing.Size(136, 24);this.button1.TabIndex = 1;

this.button1.Text = "Make XML";this.button1.Click += new System.EventHandler(this.button1_Click);

// // textBox1this.textBox1.AcceptsReturn = true;this.textBox1.AcceptsTab = true;this.textBox1.AllowDrop = true;this.textBox1.Location = new System.Drawing.Point(24, 208);this.textBox1.Multiline = true;this.textBox1.Name = "textBox1";this.textBox1.ScrollBars = System.Windows.Forms.ScrollBars.Both;this.textBox1.Size = new System.Drawing.Size(392, 144);this.textBox1.TabIndex = 2;this.textBox1.Text = "textBox1";// // Form1this.AutoScaleBaseSize = new System.Drawing.Size(5, 13);this.ClientSize = new System.Drawing.Size(432, 357);this.Controls.Add(this.textBox1);this.Controls.Add(this.button1);this.Controls.Add(this.dataGrid1);this.Name = "Form1";this.Text = "Form1";((System.ComponentModel.ISupportInitialize)(this.dataSet1)).EndInit();((System.ComponentModel.ISupportInitialize)(this.dataGrid1)).EndInit();this.ResumeLayout(false);

}#endregion

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…//// <summary>/// The main entry point for the application./// </summary>[STAThread]static void Main() {

Application.Run(new Form1());}

private void button1_Click(object sender, System.EventArgs e){

// dataSet1.WriteXml( "Course.xml");

textBox1.Text = "Writing the following XML: \r\n" + dataSet1.GetXml( )+ "\r\n";

}}

}

generate XML corresponding to data residing in dataSet1 and andwrite it in file Course.xml.

Generate XML that corresponds to data residing

in dataSet1.

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The generated Course.xml file is independently accessible …

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• The end

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ASP .NET (2)



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ASP and ADO (assumes knowledge of ADO)

• We can access a database from within a Web Application (ASP .NETprogram), by combining ASP.NET and ADO.NET.

• This results to a 3-Tier architecture. • 1st tier : client. See the GUI (front end) and interacts with it.• 2nd tier: (asp) server. Hosts the ASP.NET program.

– Hosts the .aspx and .cs files as well as the program(s) that perform ADO activities.

– Does not host the Database. – Receives requests from the 1st tier– Processes requests.– Becomes client to the 3rd tier, which hosts the data base.

• Poses DB queries to 3rd tier.• Receives responses (query results) from 3rd tier.• Processes responses of 3rd tier, assembles .html documents and sends results to 1st

tier.• 3rd tier: (db) server. Hosts the Database.

– Receives DB queries (typically in SQL) from 2nd tier. – Processes queries and generates results.– Sends results to 2nd tier.

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3rd tier (server to 2nd tier)

2nd tier (server to 1st tier; client to 3rd tier)

Client’s request receivedand a web page is generated.

3-tier architecture …1st tier (client to 2nd tier)

begin

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…2nd tier (server to 1st tier; client to 3rd tier)


2nd tier receives response and processes event:1. Creates query2. Submits query to 3rd tier

Receives query

Process Query

1st tier (client to 2nd tier)

User clicks “Show data” button.

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Generate results

2nd tier (server to 1st tier; client to 3rd tier)

Receive results (and places result

into DataSet and DataGrid).

1st tier (client to 2nd tier)

end

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Example

User is prompted for ID and password.

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Example …

1. User typed ID and password. 2. Request was sent to 2nd tier.3. 2nd tier checked … decided

that (ID,Pass) is not valid.

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Example …

1. User typed again ID and password. 2. Request was sent to 2nd tier.3. 2nd tier checked … decided that (ID,Pass) is valid.4. Responded back to 1st tier that can now proceed to

retrieve data.

User presses button.

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Example …

1. Server received button event, 2. Processed event

a) Create query, connection to DB, and sent query to 3rd tier.b) Received results of query from 3rd tier.c) Placed query results into DataGrid.d) Created web page shown here.e) Sent web page to 1st tier.

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The code This application has two

.aspx files and two .cs files.

This .cs file handles the login

process.

This .cs file handles the DB access

process.

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The code …using System.Data;using System.Drawing;using System.Web;using System.Web.SessionState;using System.Web.UI;using System.Web.UI.WebControls;using System.Web.UI.HtmlControls;

namespace WebApplication3ASPwithADO{

/// <summary>/// Summary description for WebForm1./// </summary>public class WebForm1 : System.Web.UI.Page{

protected System.Web.UI.WebControls.Label Label1;protected System.Web.UI.WebControls.Label Label2;protected System.Web.UI.WebControls.TextBox TextBox1;protected System.Web.UI.WebControls.TextBox TextBox2;protected System.Web.UI.WebControls.Label Label3;protected System.Web.UI.WebControls.Button Button1;

private void Page_Load(object sender, System.EventArgs e){

}

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…#region Web Form Designer generated codeoverride protected void OnInit(EventArgs e){

//// CODEGEN: This call is required by the ASP.NET Web Form Designer.//InitializeComponent();base.OnInit(e);

}/// <summary>/// Required method for Designer support - do not modify/// the contents of this method with the code editor./// </summary>

private void InitializeComponent(){

this.TextBox1.TextChanged += new System.EventHandler(this.TextBox1_TextChanged);this.Button1.Click += new System.EventHandler(this.Button1_Click);this.Load += new System.EventHandler(this.Page_Load);

}

#endregion

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…private void Button1_Click(object sender, System.EventArgs e){

string userID = TextBox1.Text;string userPassword = TextBox2.Text;string loginResult = ValidateUser(userID, userPassword);if (!loginResult.Equals( "Welcome") ){

Label3.Text = "INVALID LOGIN! Try again ... ";TextBox1.Text = "";TextBox2.Text = "";Page_Load(this, e); // reload page

}else {

// load and display the ADO related form

Response.Redirect( "WebForm2ForADOpartOfASPandADOApplication.aspx");}

}

private string ValidateUser(string userID, string userPassword) {

if (userID.Equals( "abc") && userPassword.Equals( "pass")){

return "Welcome";}else {

return "Invalid login.";}

}private void TextBox1_TextChanged(object sender, System.EventArgs e){}}}

If invalid login, clear textboxes and re-

prompt.

!!! Usage of a second Form here. In case of valid login,

open another Form that performs the database

access. This is not necessary, but it makes the code more modular and convenient to

write.

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WebForm2ForADOpartOfASPandADOApplication.aspx .cs

using System.Web.SessionState;using System.Web.UI;using System.Web.UI.WebControls;using System.Web.UI.HtmlControls;

namespace WebApplication3ASPwithADO{

/// <summary>/// Summary description for WebForm2ForADOpartOfASPandADOApplication./// </summary>public class WebForm2ForADOpartOfASPandADOApplication : System.Web.UI.Page{

protected System.Data.OleDb.OleDbDataAdapter oleDbDataAdapter1;protected System.Data.OleDb.OleDbCommand oleDbSelectCommand1;protected System.Data.OleDb.OleDbCommand oleDbInsertCommand1;protected System.Data.DataSet dataSet1;protected System.Web.UI.WebControls.DataGrid DataGrid1;protected System.Web.UI.WebControls.Button Button1;protected System.Web.UI.WebControls.Label Label1;protected System.Web.UI.WebControls.Label Label2;protected System.Data.OleDb.OleDbConnection oleDbConnection1;

private void Page_Load(object sender, System.EventArgs e){

// Put user code to initialize the page here}

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…#region Web Form Designer generated codeoverride protected void OnInit(EventArgs e){

//// CODEGEN: This call is required by the ASP.NET Web Form Designer.//InitializeComponent();base.OnInit(e);

}

/// <summary>/// Required method for Designer support - do not modify/// the contents of this method with the code editor./// </summary>

private void InitializeComponent(){

this.oleDbConnection1 = new System.Data.OleDb.OleDbConnection();this.oleDbDataAdapter1 = new System.Data.OleDb.OleDbDataAdapter();this.oleDbSelectCommand1 = new System.Data.OleDb.OleDbCommand();this.oleDbInsertCommand1 = new System.Data.OleDb.OleDbCommand();this.dataSet1 = new System.Data.DataSet();((System.ComponentModel.ISupportInitialize)(this.dataSet1)).BeginInit();

// // oleDbConnection1//

this.oleDbConnection1.ConnectionString = @"Jet OLEDB:Global Partial Bulk Ops=2;Jet OLEDB:Registry Path=;Jet OLEDB:Database Locking Mode=1;Data Source=""E:\4413 -- e-commerce course\__WINTER 2006\MySlides\_Slides _3 ADO NET slides\ADO .NET My code tests\MyStudentsDB.mdb"";Jet OLEDB:Engine Type=5;Provider=""Microsoft.Jet.OLEDB.4.0"";Jet OLEDB:System database=;Jet OLEDB:SFP=False;persist security info=False;Extended Properties=;Mode=Share Deny None;Jet OLEDB:Encrypt Database=False;Jet OLEDB:Create System Database=False;Jet OLEDB:Don't Copy Locale on Compact=False;Jet OLEDB:Compact Without Replica Repair=False;User ID=Admin;Jet OLEDB:Global Bulk Transactions=1";

The connection to DB.

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…// // oleDbDataAdapter1//

this.oleDbDataAdapter1.InsertCommand = this.oleDbInsertCommand1;this.oleDbDataAdapter1.SelectCommand = this.oleDbSelectCommand1;this.oleDbDataAdapter1.TableMappings.AddRange(new System.Data.Common.DataTableMapping[] {

new System.Data.Common.DataTableMapping("Table", "Enroll", new System.Data.Common.DataColumnMapping[] {

new System.Data.Common.DataColumnMapping("cno", "cno"),new System.Data.Common.DataColumnMapping("dname", "dname"),new System.Data.Common.DataColumnMapping("grade", "grade"),new System.Data.Common.DataColumnMapping("secno", "secno"),new System.Data.Common.DataColumnMapping("sid", "sid")})});

// // oleDbSelectCommand1//

this.oleDbSelectCommand1.CommandText = "SELECT cno, dname, sid, grade FROM Enroll WHERE (sid = 104)";

this.oleDbSelectCommand1.Connection = this.oleDbConnection1;// // oleDbInsertCommand1//

this.oleDbInsertCommand1.CommandText = "INSERT INTO Enroll(cno, dname, grade, secno, sid) VALUES (?, ?, ?, ?, ?)";

this.oleDbInsertCommand1.Connection = this.oleDbConnection1;this.oleDbInsertCommand1.Parameters.Add(new System.Data.OleDb.OleDbParameter("cno",

System.Data.OleDb.OleDbType.Integer, 0, "cno"));this.oleDbInsertCommand1.Parameters.Add(new System.Data.OleDb.OleDbParameter("dname",

System.Data.OleDb.OleDbType.VarWChar, 255, "dname"));this.oleDbInsertCommand1.Parameters.Add(new System.Data.OleDb.OleDbParameter("grade",

System.Data.OleDb.OleDbType.Double, 0, "grade"));this.oleDbInsertCommand1.Parameters.Add(new System.Data.OleDb.OleDbParameter("secno",

System.Data.OleDb.OleDbType.Integer, 0, "secno"));this.oleDbInsertCommand1.Parameters.Add(new System.Data.OleDb.OleDbParameter("sid",

System.Data.OleDb.OleDbType.Integer, 0, "sid"));

The query.

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…/// // dataSet1// this.dataSet1.DataSetName = "NewDataSet";this.dataSet1.Locale = new System.Globalization.CultureInfo("en-US");this.Button1.Click += new System.EventHandler(this.Button1_Click);this.Load += new System.EventHandler(this.Page_Load);((System.ComponentModel.ISupportInitialize)(this.dataSet1)).EndInit();

}#endregion

private void Button1_Click(object sender, System.EventArgs e){

Label1.Text = ".. connectiing to DB...";oleDbConnection1.Open(); // open DBLabel1.Text += "connected!";

// execute query oleDbDataAdapter1.Fill( dataSet1, "res");

Label1.Text += "... retrieved data!";

// display results to datagridDataGrid1.DataBind();DataGrid1.Visible = true;

}}}

Execute query, receive result (at 2nd tier) and

put result into dataSet1.

Populate DataGrid with results (of dataSet1) and make it visible. Note, this looks different from how it would be

done normally in a windows application. (oleDbDataAdapter1.Fill( dataSet1, "res");

DataGrid1.SetDataBinding( dataSet1, "res"); )

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The end

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Web Services in .NET (1)



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What is a Web Service?• A Web Service (WS) is a class (or many

classes) that resides in a computer and it is accessible from another computer, in the sense that clients can call methods of this class remotely.

• In .NET, any method of a class can be equipped to be accessed remotely. All it needs is to associate the attribute [WebMethod] with that method.

[ WebMethod ]

public void MyMethod( …) { …}

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Web Services vs “Local” Services …

System calls are written in some language (part of the OS).

SOAP is written in XML.

Access is done via local system calls (managed by the local operating system).

Access is done via “remote system calls” managed by HTTP and SOAP (Simple Object Access Protocol), a protocol that allows calling remote methods).

Class produces DLL file which is stored in local computer, and it is accessed from classes residing in same computer.

Class produces DLL file which is stored in local computer, and it is accessed from classes residing in some other computer

Local serviceWeb service

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Web Services vs “Local” Services …/

We learn about local methods via the API.

We learn about Web Services via UDDI (Universal Description Discovery and Integration) and DISCO. [ in practice, however, so far, we learn mostly through word-of-mouth ]

API may be written in XML.WSDL is written in XML.

Documentation for a local method is provided via a local API(Application Programming Interface).

Documentation for a web method is provided via WSDL(Web Service Description Language).

Local serviceWeb service

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Evolution of the internet and the WWW (0)[ “Web 0” , just internet]

Generation 0FTP, e-mail

HTML

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Evolution of the web (1) – [ “Web 1” ]

Generation 1Static HTML

HTML

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Evolution of the web (2) [ “Web 1+”, “Web 2.0” ]

Generation 2Web Applications

HTML

84

Evolution of the web (3)[ “Web 2.0”, “Web 3.0” ]

HTML, XML

HTML, XML

Generation 3 (under construction)Web Services

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Evolution of the web (4)

empIDHTML, XML

HTML, XML, RDF

Generation 4 (under contemplation)Semantic Web

“Web 3.0”

Be able to realize that empID and Emp-idmean the same thing.

Emp-id

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Benefits of Web Services …• May facilitate significant boost for developing

distributed applications.• Use standard (SOAP) for message exchange.• Use standard for interface description (WSDL),

in XML.• Independent of programming languages and

operating systems.• Utilize existing Internet protocols (HTTP usually,

but also SMTP and FTP).

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Benefits of Web Services …/• Web Services allow you to interconnect:

– Different companies– Many/any devices– Applications– Different clients

• Not just browsers

• Distribution and integration of application logic• Enable the programmable Web

– Not just the purely interactive Web• Loosely coupled (scale well)

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Comparison of various distributed (Web Services and ancestors) technologies

SOAPORB/CDR.NET object serialization

Java object serialization

Message exchange format

HTTP, HTTPS, SMTP, FTP

GIOP/IIOPbinary or OAPRMI-IIOPTransport protocol

XML data IDL-specified objects

.NET objects Java objects (binary)

Data exchange format

WSDL (XML-based)

CORBA IDL.NET Interfaces Java Interfaces Interface definition

independentindependent.NET languages (C#, VB.NET, ..)

Java Programming language

Web services

CORBA.NET Remoting

Java RMI

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Web services related .NET namespaces

• System.Web.Services– for developing Web services (e.g.: WebService, WebMethod)

• System.Web.Services.Configuration– for extending SOAP

• System.Web.Services.Description– for creating and manipulating WSDL descriptions

• System.Web.Services.Discovery– for using DISCO

• System.Web.Services.Protocols– for implementation of communication protocols (e.g. SOAP-

HTTP)• System.Xml.Serialization

– for XML serialization

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Example

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A .NET web service has a .asmx file associated with it. This is the equivalent of the .aspx file of ASP.net

applications.

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Running …

The operation (method) exposed by this web service

The URL of the web service

The WSDL (web service description

language)

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The name of the Web Service.

The result of invoking method

“Hello World”

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