316 Project 2 CREATING THE EMPLOYEE RECORDS SYSTEM PROJECT

//Add the Node

nodeCollect.Add(EcodeNode);

}

}

statusBarPanel1.Text=”Click on an employee code to see their record.”;

}

catch(XmlException e)

{

MessageBox.Show(“XML Exception :”+e.ToString());

}

}

Figure 14-1 displays the TreeView control populated with the employee codes.

FIGURE 14-1 The TreeView control populated with employee codes

Event Handling

An event is the result of an action that has occurred. This action could have occurred as a result of user action, such as a mouse click, or could have been the result of a built-in program logic. For example, when a person rings the doorbell, an event takes place. Another person responds to the event by attending the door. The person ringing the bell is called the event sender and the person responding is the event receiver or handler. However, the person triggering the event is not aware of the person who will be handling the event.

To respond to an event, you must provide an event handler method that will handle the events. Suppose you have a simple Windows form that contains a button. When the button is clicked, the event must be handled by an event handler method. The following code shows an event handler.

void Button_Clicked(object sender, EventArgs e)

{

//the program logic

}

However, for the event to be handled, you need to tie up your event handler to an instance of the button. You need to create an instance of EventHandler that takes a reference to Button_Clicked as its argument, as shown in the following code:

button.Click+=new EventHandler(this.Button_Clicked);

This tying up is taken care of by Visual Studio .NET. The following example shows a simple Windows application that handles a button click event.

using System;

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

public class EventSampleForm: Form

{

private Button button;

public EventSampleForm () : base()

{

button = new Button(); button.Location = new Point(50,100); button.Text = “Click Me”;

// To wire the event, create a delegate instance and add it to the Click event. button.Click += new EventHandler(this.Button_Clicked);

Controls.Add(button);

}

// The event handler.

private void Button_Clicked(object sender, EventArgs e)

listView1.Columns.Add(“Date of Join”,70,HorizontalAlignment.Right );

listView1.Columns.Add(“Grade”,105,HorizontalAlignment.Left );

listView1.Columns.Add(“Salary”,105,HorizontalAlignment.Left );

}

The Columns property of the ListView class contains a collection of all the column headers that appear in the control. The Columns property returns a collection containing ColumnHeader objects that are displayed in the ListView control. The ColumnHeader objects define the text to be displayed for a column and is contained

in the ListView.ColumnHeaderCollection.

You can add a column header to the collection using the Add method. Alternatively, you can create an array of ColumnHeader objects and pass it to the AddRange method to add a number of column headers.

Table 14-4 explains some of the commonly used methods of the ListView.Column-

HeaderCollection.

Table 14-4 ListView.ColumnHeaderCollection Members

The final task is to read the EmpRec.xml XML file and display the details of an employee whose employee code has been clicked in the TreeView control.

protected void PopulateListView(TreeNode currNode)

{

initializeListControl();

Figure 14-2 displays the ERS application populated with the employee records.

FIGURE 14-2 The ERS application

The code for the entire application is given here.

using System;

using System.Drawing; using System.Collections;

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

using System.Xml;

using System.Diagnostics; using System.IO; namespace EmployeeRecords

{

///<summary>

///Summary description for Form1.

///</summary>

public class EmployeeRecordsForm : System.Windows.Forms.Form

{

private System.Windows.Forms.TreeView treeView1; private System.Windows.Forms.ListView listView1; private System.Windows.Forms.StatusBar statusBar1;

private System.Windows.Forms.StatusBarPanel statusBarPanel1;

322Project 2 CREATING THE EMPLOYEE RECORDS SYSTEM PROJECT

///<summary>

///Required designer variable.

///</summary>

private System.ComponentModel.Container components=null; private TreeNode tvRootNode;

public EmployeeRecordsForm()

{

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

//TODO: Add any constructor code after InitializeComponent call PopulateTreeView();

initializeListControl();

}

///<summary>

///Clean up any resources being used.

///</summary>

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>

private void InitializeComponent()

{

this.treeView1 = new System.Windows.Forms.TreeView(); this.listView1 = new System.Windows.Forms.ListView(); this.statusBar1 = new System.Windows.Forms.StatusBar(); this.statusBarPanel1 = new System.Windows.Forms.StatusBarPanel();

((System.ComponentModel.ISupportInitialize)(this.statusBarPanel1))

.BeginInit();

this.SuspendLayout(); this.treeView1.ImageIndex = -1; this.treeView1.Name = “treeView1”; this.treeView1.SelectedImageIndex = -1;

this.treeView1.Size = new System.Drawing.Size(240, 352); this.treeView1.TabIndex = 0;

this.treeView1.AfterSelect += new System.Windows.Forms.TreeViewEventHandler (this.treeView1_AfterSelect);

//

// listView1

//

this.listView1.Activation = System.Windows.Forms.ItemActivation.TwoClick; this.listView1.Location = new System.Drawing.Point(240, 0); this.listView1.Name = “listView1”;

this.listView1.Size = new System.Drawing.Size(480, 352); this.listView1.TabIndex = 1;

this.listView1.View = System.Windows.Forms.View.Details;

//

//statusBar1

this.statusBar1.Location = new System.Drawing.Point(0, 357); this.statusBar1.Name = “statusBar1”;

this.statusBar1.Panels.AddRange(new System.Windows.Forms.StatusBarPanel[] { this.statusBarPanel1});

this.statusBar1.ShowPanels = true;

this.statusBar1.Size = new System.Drawing.Size(720, 24); this.statusBar1.TabIndex = 2;

//statusBarPanel1

//

this.statusBarPanel1.Text = “Click the employee code to view details”;

this.statusBarPanel1.Width = 720;

//

// EmployeeRecordsForm

//

try

{

while(reader.Read())

{

if(reader.HasAttributes && reader.NodeType==XmlNodeType.Element)

{

reader.MoveToElement(); reader.MoveToElement(); reader.MoveToAttribute(“Id”); strVal=reader.Value; reader.Read(); reader.Read(); if(reader.Name==”Dept”)

{

reader.Read();

}

//create the child nodes

TreeNode EcodeNode = new TreeNode(strVal);

//Add the Node

nodeCollect.Add(EcodeNode);

}

}

statusBarPanel1.Text=”Click on an employee code to see their record.”;

}

catch(XmlException e)

{

MessageBox.Show(“XML Exception :”+e.ToString());

}

}

protected void initializeListControl()

{

listView1.Clear();

listView1.Columns.Add(“Employee Name”,225,HorizontalAlignment.Left ); listView1.Columns.Add(“Date of Join”,70,HorizontalAlignment.Right ); listView1.Columns.Add(“Grade”,105,HorizontalAlignment.Left );