 2002 Prentice Hall. All rights reserved. 1 Chapter 19 – Database, SQL, and ADO.NET Outline 19.1 Introduction 19.2 Relational Database Model 19.3 Relational Database Overview: Books Database 19.4 Structured Query Language (SQL) Basic SELECT Query WHERE Clause ORDER BY Clause Merging Data from Multiple Tables: INNER JOIN Joining Data from Tables Authors, AuthorISBN, Titles and Publishers INSERT Statement UPDATE Statement DELETE Statement

 2002 Prentice Hall. All rights reserved. 2 Chapter 19 – Database, SQL, and ADO.NET Outline 19.5 ADO.NET Object Model 19.6 Programming with ADO.NET: Extracting Information from a DBMS Connecting to and Querying an Access Data Source Querying the Books Database 19.7 Programming with ADO.NET: Modifying a DBMS 19.8 Reading and Writing XML Files

 2002 Prentice Hall. All rights reserved ADO.NET and Object Model Provides an API for accessing database systems programmatically DataSets act as caches: – Store data from source in local memory

 2002 Prentice Hall. All rights reserved Programming with ADO.NET: Extracting Information from a DBMS Examples that demonstrate how to connect to a database, query the database and display the results of the query

 2002 Prentice Hall. All rights reserved Connecting to and Querying an Access Data Source Retrieves data and stores it in a DataGrid

 2002 Prentice Hall. All rights reserved. Outline 6 TableDisplay.cs 1 // Fig : TableDisplay.cs 2 // Displays data from a database table. 3 4 using System; 5 using System.Drawing; 6 using System.Collections; 7 using System.ComponentModel; 8 using System.Windows.Forms; 9 using System.Data; // Summary description for TableDisplay.cs. 12 public class TableDisplay : System.Windows.Forms.Form 13 { 14 private System.Data.DataSet dataSet1; 15 private System.Data.OleDb.OleDbDataAdapter oleDbDataAdapter1; 16 private System.Windows.Forms.DataGrid dataGrid1; 17 private System.Data.OleDb.OleDbCommand oleDbSelectCommand1; 18 private System.Data.OleDb.OleDbCommand oleDbInsertCommand1; 19 private System.Data.OleDb.OleDbCommand oleDbUpdateCommand1; 20 private System.Data.OleDb.OleDbCommand oleDbDeleteCommand1; 21 private System.Data.OleDb.OleDbConnection oleDbConnection1; private System.ComponentModel.Container components = null; public TableDisplay() 26 { 27 InitializeComponent(); // Fill dataSet1 with data 30 oleDbDataAdapter1.Fill( dataSet1, "Authors" ); // bind data in Users table in dataSet1 to dataGrid1 33 dataGrid1.SetDataBinding( dataSet1, "Authors" ); 34 } 35 Constructor to populate dataSet1Call method fill to retrieve data from database associated with oleDbConnection Bind DataGrid to data source

 2002 Prentice Hall. All rights reserved. Outline 7 TableDisplay.cs 36 private void InitializeComponent() 37 { 38 this.dataSet1 = new System.Data.DataSet(); 39 this.oleDbDataAdapter1 = 40 new System.Data.OleDb.OleDbDataAdapter(); 41 this.dataGrid1 = new System.Windows.Forms.DataGrid(); 42 this.oleDbSelectCommand1 = 43 new System.Data.OleDb.OleDbCommand(); 44 this.oleDbInsertCommand1 = 45 new System.Data.OleDb.OleDbCommand(); 46 this.oleDbUpdateCommand1 = 47 new System.Data.OleDb.OleDbCommand(); 48 this.oleDbDeleteCommand1 = 49 new System.Data.OleDb.OleDbCommand(); 50 this.oleDbConnection1 = 51 new System.Data.OleDb.OleDbConnection(); 52 ((System.ComponentModel.ISupportInitialize) 53 (this.dataSet1)).BeginInit(); 54 ((System.ComponentModel.ISupportInitialize) 55 (this.dataGrid1)).BeginInit(); 56 this.SuspendLayout(); 57 // 58 // dataSet1 59 // 60 this.dataSet1.DataSetName = "NewDataSet"; 61 this.dataSet1.Locale = 62 new System.Globalization.CultureInfo("en-US"); 63 // 64 // oleDbDataAdapter1 65 // 66 this.oleDbDataAdapter1.DeleteCommand = 67 this.oleDbDeleteCommand1; 68 this.oleDbDataAdapter1.InsertCommand = 69 this.oleDbInsertCommand1; Specify how oleDbDataAdapter deletes data Specify how oleDbDataAdapter inserts data

 2002 Prentice Hall. All rights reserved. Outline 8 TableDisplay.cs 70 this.oleDbDataAdapter1.SelectCommand = 71 this.oleDbSelectCommand1; 72 this.oleDbDataAdapter1.TableMappings.AddRange( 73 new System.Data.Common.DataTableMapping[] { 74 new System.Data.Common.DataTableMapping( 75 "Table", "Authors", 76 new System.Data.Common.DataColumnMapping[] { 77 new System.Data.Common.DataColumnMapping( 78 "authorID", "authorID"), 79 new System.Data.Common.DataColumnMapping( 80 "firstName", "firstName"), 81 new System.Data.Common.DataColumnMapping( 82 "lastName", "lastName")})}); 83 this.oleDbDataAdapter1.UpdateCommand = 84 this.oleDbUpdateCommand1; 85 // 86 // dataGrid1 87 // 88 this.dataGrid1.DataMember = ""; 89 this.dataGrid1.HeaderForeColor = 90 System.Drawing.SystemColors.ControlText; 91 this.dataGrid1.Location = 92 new System.Drawing.Point(16, 16); 93 this.dataGrid1.Name = "dataGrid1"; 94 this.dataGrid1.Size = new System.Drawing.Size(264, 248); 95 this.dataGrid1.TabIndex = 0; 96 // 97 // oleDbSelectCommand1 98 // 99 this.oleDbSelectCommand1.CommandText = 100 "SELECT authorID, firstName, lastName FROM Authors"; 101 this.oleDbSelectCommand1.Connection = 102 this.oleDbConnection1; Specify how oleDbDataAdapter selects data Specify how oleDbDataAdapter updates data

 2002 Prentice Hall. All rights reserved. Outline 9 TableDisplay.cs 103 // 104 // oleDbInsertCommand1 105 // 106 this.oleDbInsertCommand1.CommandText = 107 "INSERT INTO Authors(firstName, lastName) VALUES " "(?, ?)"; 109 this.oleDbInsertCommand1.Connection = 110 this.oleDbConnection1; 111 this.oleDbInsertCommand1.Parameters.Add( 112 new System.Data.OleDb.OleDbParameter("firstName", 113 System.Data.OleDb.OleDbType.VarWChar, 50, 114 "firstName")); 115 this.oleDbInsertCommand1.Parameters.Add( 116 new System.Data.OleDb.OleDbParameter("lastName", 117 System.Data.OleDb.OleDbType.VarWChar, 50, 118 "lastName")); 119 // 120 // oleDbUpdateCommand1 121 // 122 this.oleDbUpdateCommand1.CommandText = 123 "UPDATE Authors SET firstName = ?, lastName = ? WHERE" " (authorID = ?) AND (firstNam" "e = ? OR ? IS NULL AND firstName IS NULL) AND " "(lastName = ? OR ? IS NULL AND las" "tName IS NULL)"; 128 this.oleDbUpdateCommand1.Connection = 129 this.oleDbConnection1; 130 this.oleDbUpdateCommand1.Parameters.Add( 131 new System.Data.OleDb.OleDbParameter( 132 "firstName", 133 System.Data.OleDb.OleDbType.VarWChar, , "firstName")); 135 this.oleDbUpdateCommand1.Parameters.Add( 136 new System.Data.OleDb.OleDbParameter( 137 "lastName", Set connection property for oleDbUpdageCommand1 Set CommandText for oleDbUpdageCommand1

 2002 Prentice Hall. All rights reserved. Outline 10 TableDisplay.cs 138 System.Data.OleDb.OleDbType.VarWChar, 50, 139 "lastName")); 140 this.oleDbUpdateCommand1.Parameters.Add( 141 new System.Data.OleDb.OleDbParameter( 142 "Original_authorID", 143 System.Data.OleDb.OleDbType.Integer, 0, 144 System.Data.ParameterDirection.Input, false, 145 ((System.Byte)(10)), ((System.Byte)(0)), 146 "authorID", System.Data.DataRowVersion.Original, 147 null)); 148 this.oleDbUpdateCommand1.Parameters.Add( 149 new System.Data.OleDb.OleDbParameter( 150 "Original_firstName", 151 System.Data.OleDb.OleDbType.VarWChar, 50, 152 System.Data.ParameterDirection.Input, false, 153 ((System.Byte)(0)), ((System.Byte)(0)), 154 "firstName", System.Data.DataRowVersion.Original, 155 null)); 156 this.oleDbUpdateCommand1.Parameters.Add( 157 new System.Data.OleDb.OleDbParameter( 158 "Original_firstName1", 159 System.Data.OleDb.OleDbType.VarWChar, 50, 160 System.Data.ParameterDirection.Input, false, 161 ((System.Byte)(0)), ((System.Byte)(0)), 162 "firstName", System.Data.DataRowVersion.Original, 163 null)); 164 this.oleDbUpdateCommand1.Parameters.Add( 165 new System.Data.OleDb.OleDbParameter( 166 "Original_lastName", 167 System.Data.OleDb.OleDbType.VarWChar, 50, 168 System.Data.ParameterDirection.Input, false, 169 ((System.Byte)(0)), ((System.Byte)(0)), 170 "lastName", System.Data.DataRowVersion.Original, 171 null));

 2002 Prentice Hall. All rights reserved. Outline 11 TableDisplay.cs 172 this.oleDbUpdateCommand1.Parameters.Add( 173 new System.Data.OleDb.OleDbParameter( 174 "Original_lastName1", 175 System.Data.OleDb.OleDbType.VarWChar, 50, 176 System.Data.ParameterDirection.Input, false, 177 ((System.Byte)(0)), ((System.Byte)(0)), 178 "lastName", System.Data.DataRowVersion.Original, 179 null)); 180 // 181 // oleDbDeleteCommand1 182 // 183 this.oleDbDeleteCommand1.CommandText = 184 "DELETE FROM Authors WHERE (authorID = ?) AND " "(firstName = ? OR ? IS NULL AND firs" "tName IS NULL) AND (lastName = ? OR ? IS NULL AND " "lastName IS NULL)"; 188 this.oleDbDeleteCommand1.Connection = 189 this.oleDbConnection1; 190 this.oleDbDeleteCommand1.Parameters.Add( 191 new System.Data.OleDb.OleDbParameter( 192 "Original_authorID", 193 System.Data.OleDb.OleDbType.Integer, 0, 194 System.Data.ParameterDirection.Input, false, 195 ((System.Byte)(10)), ((System.Byte)(0)), 196 "authorID", System.Data.DataRowVersion.Original, 197 null)); 198 this.oleDbDeleteCommand1.Parameters.Add( 199 new System.Data.OleDb.OleDbParameter( 200 "Original_firstName", 201 System.Data.OleDb.OleDbType.VarWChar, 50, 202 System.Data.ParameterDirection.Input, false, 203 ((System.Byte)(0)), ((System.Byte)(0)), 204 "firstName", System.Data.DataRowVersion.Original, 205 null));

 2002 Prentice Hall. All rights reserved. Outline 12 TableDisplay.cs 206 this.oleDbDeleteCommand1.Parameters.Add( 207 new System.Data.OleDb.OleDbParameter( 208 "Original_firstName1", 209 System.Data.OleDb.OleDbType.VarWChar, 50, 210 System.Data.ParameterDirection.Input, false, 211 ((System.Byte)(0)), ((System.Byte)(0)), 212 "firstName", System.Data.DataRowVersion.Original, 213 null)); 214 this.oleDbDeleteCommand1.Parameters.Add( 215 new System.Data.OleDb.OleDbParameter( 216 "Original_lastName", 217 System.Data.OleDb.OleDbType.VarWChar, 50, 218 System.Data.ParameterDirection.Input, false, 219 ((System.Byte)(0)), ((System.Byte)(0)), 220 "lastName", System.Data.DataRowVersion.Original, 221 null)); 222 this.oleDbDeleteCommand1.Parameters.Add( 223 new System.Data.OleDb.OleDbParameter( 224 "Original_lastName1", 225 System.Data.OleDb.OleDbType.VarWChar, 50, 226 System.Data.ParameterDirection.Input, false, 227 ((System.Byte)(0)), ((System.Byte)(0)), 228 "lastName", System.Data.DataRowVersion.Original, 229 null)); 230 // 231 // oleDbConnection1 232 //

 2002 Prentice Hall. All rights reserved. Outline 13 TableDisplay.cs 233 this.oleDbConnection1.ConnectionString = + ID=Admin;Data Source=C:\Books\2001\csphtp1\" + " + None;Extended Properties="""";Jet OLEDB:" + database="""";Jet OLEDB:Registry " + OLEDB:Database Password="""";" + OLEDB:Engine Type=5;Jet OLEDB:Database " + Mode=1;Jet OLEDB:Global Partial Bulk " + OLEDB:Global Bulk Transactions=1;Jet " + Database Password="""";Jet OLEDB:" + System Database=False;Jet OLEDB:Encrypt " + OLEDB:Don't Copy Locale on " + OLEDB:Compact Without Replica " + OLEDB:SFP=False"; 248 // 249 // TableDisplay 250 // 251 this.AutoScaleBaseSize = new System.Drawing.Size(5, 13); 252 this.ClientSize = new System.Drawing.Size(292, 273); 253 this.Controls.AddRange( 254 new System.Windows.Forms.Control[] { 255 this.dataGrid1}); 256 this.Name = "TableDisplay"; 257 this.Text = "TableDisplay"; 258 ((System.ComponentModel.ISupportInitialize) 259 (this.dataSet1)).EndInit(); 260 ((System.ComponentModel.ISupportInitialize) 261 (this.dataGrid1)).EndInit(); 262 this.ResumeLayout(false); 263 Initialize oleDbConnection, and specify path to database

 2002 Prentice Hall. All rights reserved. Outline 14 TableDisplay.cs Program Output 264 } // end of InitializeComponent [STAThread] 267 static void Main() 268 { 269 Application.Run( new TableDisplay() ); 270 } 271 }

 2002 Prentice Hall. All rights reserved Querying the Books Database Use SELECT statements on database and display results

 2002 Prentice Hall. All rights reserved. Outline 16 DisplayQueryResu lts.cs 1 // Fig : DisplayQueryResults.cs 2 // Displays the contents of the authors database. 3 4 using System; 5 using System.Drawing; 6 using System.Collections; 7 using System.ComponentModel; 8 using System.Windows.Forms; 9 using System.Data; public class DisplayQueryResults : System.Windows.Forms.Form 12 { 13 private System.Data.OleDb.OleDbConnection oleDbConnection1; 14 private System.Data.DataSet dataSet1; 15 private System.Data.OleDb.OleDbDataAdapter oleDbDataAdapter1; 16 private System.Data.OleDb.OleDbCommand oleDbSelectCommand1; 17 private System.Data.OleDb.OleDbCommand oleDbInsertCommand1; 18 private System.Data.OleDb.OleDbCommand oleDbUpdateCommand1; 19 private System.Data.OleDb.OleDbCommand oleDbDeleteCommand1; 20 private System.Windows.Forms.TextBox queryTextBox; 21 private System.Windows.Forms.Button submitButton; 22 private System.Windows.Forms.DataGrid dataGrid1; 23 private System.ComponentModel.Container components = null; public DisplayQueryResults() 26 { InitializeComponent(); 29 } // Visual Studio.NET generated code 32

 2002 Prentice Hall. All rights reserved. Outline 17 DisplayQueryResu lts.cs 33 [STAThread] 34 static void Main() 35 { 36 Application.Run( new DisplayQueryResults() ); 37 } // perform SQL query on data 40 private void submitButton_Click( object sender, 41 System.EventArgs e ) 42 { 43 try 44 { 45 // set SQL query to what user 46 // input into queryTextBox 47 oleDbDataAdapter1.SelectCommand.CommandText = 48 queryTextBox.Text; // clear DataSet from previous operation 51 dataSet1.Clear(); // Fill data set with information that results 54 // from SQL query 55 oleDbDataAdapter1.Fill( dataSet1, "Authors" ); // bind DataGrid to contents of DataSet 58 dataGrid1.SetDataBinding( dataSet1, "Authors" ); 59 } catch ( System.Data.OleDb.OleDbException oleException ) 62 { 63 MessageBox.Show( "Invalid query" ); 64 } } // end of submitButton_Click 67 } When user clicks submit button, assign SELECT query string to OleDbDataAdapter’s SelectCommand property Place data from database into dataSet1 Bind DataGrid to data and display results

 2002 Prentice Hall. All rights reserved. Outline 18 DisplayQueryResu lts.cs Program Output

 2002 Prentice Hall. All rights reserved Programming with ADO.NET: Modifying a DBMS Example implements an address book –User can insert, locate and update records

 2002 Prentice Hall. All rights reserved. Outline 20 AddressBook.cs 1 // Fig : AddressBook.cs 2 // Using SQL statements to manipulate a database. 3 4 using System; 5 using System.Drawing; 6 using System.Collections; 7 using System.ComponentModel; 8 using System.Windows.Forms; 9 using System.Data; public class AddressBook : System.Windows.Forms.Form 12 { 13 private System.Windows.Forms.TextBox faxTextBox; 14 private System.Windows.Forms.TextBox homeTextBox; 15 private System.Windows.Forms.TextBox firstTextBox; 16 private System.Windows.Forms.TextBox stateTextBox; 17 private System.Windows.Forms.TextBox idTextBox; 18 private System.Windows.Forms.TextBox lastTextBox; 19 private System.Windows.Forms.TextBox postalTextBox; 20 private System.Windows.Forms.TextBox addressTextBox; 21 private System.Windows.Forms.TextBox cityTextBox; 22 private System.Windows.Forms.TextBox countryTextBox; 23 private System.Windows.Forms.TextBox TextBox; 24 private System.Data.DataSet dataSet1; 25 private System.Data.OleDb.OleDbDataAdapter oleDbDataAdapter1; 26 private System.Data.OleDb.OleDbCommand oleDbSelectCommand1; 27 private System.Data.OleDb.OleDbCommand oleDbInsertCommand1; 28 private System.Data.OleDb.OleDbCommand oleDbUpdateCommand1; 29 private System.Data.OleDb.OleDbCommand oleDbDeleteCommand1; 30 private System.Data.OleDb.OleDbConnection oleDbConnection1; 31 private System.Windows.Forms.TextBox statusTextBox; 32 private System.Windows.Forms.Label addressLabel; 33 private System.Windows.Forms.Label cityLabel; 34 private System.Windows.Forms.Label stateLabel; 35 private System.Windows.Forms.Label idLabel;

 2002 Prentice Hall. All rights reserved. Outline 21 AddressBook.cs 36 private System.Windows.Forms.Label firstLabel; 37 private System.Windows.Forms.Label lastLabel; 38 private System.Windows.Forms.Label postalLabel; 39 private System.Windows.Forms.Label countryLabel; 40 private System.Windows.Forms.Label Label; 41 private System.Windows.Forms.Button clearButton; 42 private System.Windows.Forms.Button helpButton; 43 private System.Windows.Forms.Button findButton; 44 private System.Windows.Forms.Button addButton; 45 private System.Windows.Forms.Button updateButton; 46 private System.Windows.Forms.Label faxLabel; 47 private System.Windows.Forms.Label homeLabel; 48 private System.ComponentModel.Container components = null; public AddressBook() 51 { 52 InitializeComponent(); 53 oleDbConnection1.Open(); 54 } // Visual Studio.NET generated code [STAThread] 59 static void Main() 60 { 61 Application.Run( new AddressBook() ); 62 } private void findButton_Click( object sender, 65 System.EventArgs e ) 66 { 67 try 68 { Perform SELECT query on database

 2002 Prentice Hall. All rights reserved. Outline 22 AddressBook.cs 69 if ( lastTextBox.Text != "" ) 70 { 71 // clear DataSet from last operation 72 dataSet1.Clear(); // create SQL query to find contact with 75 // specified last name 76 oleDbDataAdapter1.SelectCommand.CommandText = 77 "SELECT * FROM addresses WHERE lastname = '" + 78 lastTextBox.Text + "'"; // fill dataSet1 with rows resulting from 81 // query 82 oleDbDataAdapter1.Fill( dataSet1 ); // display information 85 Display( dataSet1 ); 86 statusTextBox.Text += "\r\nQuery successful\r\n"; 87 } 88 else 89 lastTextBox.Text = 90 "Enter last name here then press Find"; 91 } catch ( System.Data.OleDb.OleDbException oleException ) 94 { 95 Console.WriteLine( oleException.StackTrace ); 96 statusTextBox.Text += oleException.ToString(); 97 } 98 Empty DataSet of prior data Modify SQL query’s text to perform SELECT operation Fill DataSet with query results Display data in textboxes

 2002 Prentice Hall. All rights reserved. Outline 23 AddressBook.cs 99 catch ( InvalidOperationException invalidException ) 100 { 101 MessageBox.Show( invalidException.Message ); 102 } } // end of findButton_Click private void addButton_Click( object sender, System.EventArgs e ) 107 { 108 try 109 { 110 if ( lastTextBox.Text != "" && firstTextBox.Text != "" ) 111 { 112 // create SQL query to insert row 113 oleDbDataAdapter1.InsertCommand.CommandText = 114 "INSERT INTO addresses (" "firstname, lastname, address, city, " "stateorprovince, postalcode, country, " " address, homephone, faxnumber" ") VALUES ('" firstTextBox.Text + "', '" lastTextBox.Text + "', '" addressTextBox.Text + "', '" cityTextBox.Text + "', '" stateTextBox.Text + "', '" postalTextBox.Text + "', '" countryTextBox.Text + "', '" TextBox.Text + "', '" homeTextBox.Text + "', '" faxTextBox.Text + "')"; // notify user that query is being sent 131 statusTextBox.Text += "\r\nSending query: " oleDbDataAdapter1.InsertCommand.CommandText "\r\n" ; Perform INSERT operation using OleDbCommand members Sets CommandText property of InsertCommand to execute proper INSERT statement

 2002 Prentice Hall. All rights reserved. Outline 24 AddressBook.cs // send query 136 oleDbDataAdapter1.InsertCommand.ExecuteNonQuery(); statusTextBox.Text += "\r\nQuery successful\r\n"; 139 } 140 else 141 statusTextBox.Text += "\r\nEnter at least first " "and last name then press Add\r\n"; 143 } catch ( System.Data.OleDb.OleDbException oleException ) 146 { 147 Console.WriteLine( oleException.StackTrace ); 148 statusTextBox.Text += oleException.ToString(); 149 } } // end of addButton_Click private void updateButton_Click( object sender, 154 System.EventArgs e ) 155 { 156 try 157 { 158 // make sure users have found record 159 // they wish to update 160 if ( idTextBox.Text != "" ) 161 { 162 // set SQL query to update all fields in 163 // table where id number matches id 164 // in idTextBox 165 oleDbDataAdapter1.UpdateCommand.CommandText = 166 "UPDATE addresses SET " "firstname ='" + firstTextBox.Text "', lastname='" + lastTextBox.Text + Perform UPDATE operation using OleDbCommand members Send inset query to perform INSERT operation Sets CommandText property of UpdateCommand to execute proper Update statement

 2002 Prentice Hall. All rights reserved. Outline 25 AddressBook.cs 169 "', address='" + addressTextBox.Text "', city='" + cityTextBox.Text "', stateorprovince='" + stateTextBox.Text "', postalcode='" + postalTextBox.Text "', country='" + countryTextBox.Text "', address='" + TextBox.Text "', homephone='" + homeTextBox.Text "', faxnumber='" + faxTextBox.Text "' WHERE id=" + idTextBox.Text; // notify user that query is being set 180 statusTextBox.Text += "\r\nSending query: " oleDbDataAdapter1.UpdateCommand.CommandText "\r\n"; // execute query 185 oleDbDataAdapter1.UpdateCommand.ExecuteNonQuery(); statusTextBox.Text += "\r\nQuery successful\r\n"; 188 } 189 else 190 statusTextBox.Text += "\r\nYou may only update " "an existing record. Use Find to locate the" "record, then modify the information and " "press Update.\r\n"; 194 } catch ( System.Data.OleDb.OleDbException oleException ) 197 { 198 Console.WriteLine( oleException.StackTrace ); 199 statusTextBox.Text += oleException.ToString(); 200 } } // end of updateButton_Click 203 Send update query to perform UPDATE operation

 2002 Prentice Hall. All rights reserved. Outline 26 AddressBook.cs 204 private void clearButton_Click( object sender, 205 System.EventArgs e ) 206 { 207 idTextBox.Clear(); 208 ClearTextBoxes(); 209 } private void helpButton_Click( object sender, 212 System.EventArgs e ) 213 { 214 statusTextBox.AppendText( 215 "\r\nClick Find to locate a record\r\n" "Click Add to insert a new record.\r\n" "Click Update to update the information in a record " "\r\nClick Clear to empty the textboxes" ); 219 } private void Display( DataSet dataSet ) 222 { 223 try 224 { 225 // get first DataTable--there always will be one 226 DataTable dataTable = dataSet.Tables[ 0 ]; if ( dataTable.Rows.Count != 0 ) 229 { 230 int recordNumber = ( int ) dataTable.Rows[ 0 ][ 0 ]; idTextBox.Text = recordNumber.ToString(); 233 firstTextBox.Text = 234 ( string ) dataTable.Rows[ 0 ][ 1 ]; 235 lastTextBox.Text = 236 ( string ) dataTable.Rows[ 0 ][ 2 ]; 237 addressTextBox.Text = 238 ( string ) dataTable.Rows[ 0 ][ 3 ]; Updates display with data acquired by query DataTable from DataSet, contains results of query Determine if query returned any rows Retrieve first field of database Retrieve the rest of the fields of database Display instructions if user clicks help Clear textboxes if user clicks clear

 2002 Prentice Hall. All rights reserved. Outline 27 AddressBook.cs 239 cityTextBox.Text = 240 ( string ) dataTable.Rows[ 0 ][ 4 ]; 241 stateTextBox.Text = 242 ( string ) dataTable.Rows[ 0 ][ 5 ]; 243 postalTextBox.Text = 244 ( string ) dataTable.Rows[ 0 ][ 6 ]; 245 countryTextBox.Text = 246 ( string ) dataTable.Rows[ 0 ][ 7 ]; 247 TextBox.Text = 248 ( string ) dataTable.Rows[ 0 ][ 8 ]; 249 homeTextBox.Text = 250 ( string ) dataTable.Rows[ 0 ][ 9 ]; 251 faxTextBox.Text = 252 ( string ) dataTable.Rows[ 0 ][ 10 ]; 253 } else 256 statusTextBox.Text += "\r\nNo record found\r\n"; 257 } catch( System.Data.OleDb.OleDbException oleException ) 260 { 261 Console.WriteLine( oleException.StackTrace ); 262 statusTextBox.Text += oleException.ToString(); 263 } } // end Display private void ClearTextBoxes() 268 { 269 firstTextBox.Clear(); 270 lastTextBox.Clear(); 271 addressTextBox.Clear(); 272 cityTextBox.Clear(); 273 stateTextBox.Clear();

 2002 Prentice Hall. All rights reserved. Outline 28 AddressBook.cs Program Output 274 postalTextBox.Clear(); 275 countryTextBox.Clear(); 276 TextBox.Clear(); 277 homeTextBox.Clear(); 278 faxTextBox.Clear(); 279 } 280 }

 2002 Prentice Hall. All rights reserved. Outline 29 AddressBook.cs Program Output

 2002 Prentice Hall. All rights reserved. Outline 30 AddressBook.cs Program Output

 2002 Prentice Hall. All rights reserved. Outline 31 AddressBook.cs Program Output

 2002 Prentice Hall. All rights reserved Reading and Writing XML Files ADO.NET can convert data from data source into XML files –Uses methods WriteXml, ReadXml andGetXml

 2002 Prentice Hall. All rights reserved. Outline 33 XMLWriter.cs 1 // Fig XMLWriter.cs 2 // Demonstrates generating XML from an ADO.NET DataSet. 3 4 using System; 5 using System.Drawing; 6 using System.Collections; 7 using System.ComponentModel; 8 using System.Windows.Forms; 9 using System.Data; public class DatabaseXMLWriter : System.Windows.Forms.Form 12 { 13 private System.Data.OleDb.OleDbConnection baseballConnection; 14 private System.Data.OleDb.OleDbDataAdapter playersDataAdapter; 15 private System.Data.OleDb.OleDbCommand oleDbSelectCommand1; 16 private System.Data.OleDb.OleDbCommand oleDbInsertCommand1; 17 private System.Data.OleDb.OleDbCommand oleDbUpdateCommand1; 18 private System.Data.OleDb.OleDbCommand oleDbDeleteCommand1; 19 private System.Data.DataSet playersDataSet; 20 private System.Windows.Forms.DataGrid playersDataGrid; 21 private System.Windows.Forms.Button writeButton; 22 private System.Windows.Forms.TextBox outputTextBox; 23 private System.ComponentModel.Container components = null; public DatabaseXMLWriter() 26 { 27 // 28 // Required for Windows Form Designer support 29 // 30 InitializeComponent(); // open database connection 33 baseballConnection.Open(); 34 Create connection to database

 2002 Prentice Hall. All rights reserved. Outline 34 XMLWriter.cs 35 // fill DataSet with data from OleDbDataAdapter 36 playersDataAdapter.Fill( playersDataSet, "Players" ); // bind DataGrid to DataSet 39 playersDataGrid.SetDataBinding( playersDataSet, "Players" ); } // Visual Studio.NET generated code // main entry point for application. 46 [STAThread] 47 static void Main() 48 { 49 Application.Run( new DatabaseXMLWriter() ); 50 } // write XML representation of DataSet when button is clicked 53 private void writeButton_Click( 54 object sender, System.EventArgs e) 55 { 56 // write XML representation of DataSet to file 57 playersDataSet.WriteXml( "Players.xml" ); // display XML in TextBox 60 outputTextBox.Text += "Writing the following XML:\n\n" + 61 playersDataSet.GetXml() + "\n\n"; } 64 } Populate playersDataSet with data from database Bind DataGrid to DataSet to display data Create XML representation of data when user clicks button Append XML representation to textbox

 2002 Prentice Hall. All rights reserved. Outline 35 XMLWriter.cs

 2002 Prentice Hall. All rights reserved Reading and Writing XML Documents Fig XML document generated from DataSet in DatabaseXMLWriter.