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Summary

In this chapter, you were introduced to the case study and design of the ERS project. You created the high-level and low-level design of the application. You also learned about different controls and the means of using them. You will learn to develop the application in the next chapter.

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312 Project 2 CREATING THE EMPLOYEE RECORDS SYSTEM PROJECT

In this chapter, you will learn to add nodes to the tree view and items to the list view programmatically. You will also learn to read contents of an XML file. You

will build the Employee Records System application.

Populating the TreeView Control

In order to build the application, the first task you need to complete is populating the TreeView control. You have inserted a TreeView control in the form. However, the TreeView control does not contain any nodes. Now you will learn to add nodes to the control programmatically.

In order to add a node, you first need to initialize a new instance of the TreeNode class. Calling the constructor of the TreeNode class enables you to achieve this.The constructor of the TreeNode class is overloaded, as explained in Table 14-1.

Table 14-1 TreeNode Class Constructors

Constructor Description

Displaying Employee Codes in the TreeView Control

You can add a node to the TreeView control using the Add method, as follows:

treeview1.Nodes.Add(new TreeNode(“Root Node”)

In this code, treeview1 refers to the TreeView control. The Nodes collection contains all child nodes of a particular parent node. The Add method of the TreeNodeCollection class enables you to add nodes to the collection. For example, the following code explains the manner in which you can add a node with the display

text “My Computer”.

tnRootNode = new TreeNode(“My Computer”); tvFolderView.Nodes.Add(tnRootNode);

The previous code assumes that you have added a TreeView control to the form.

The first task that you need to accomplish is to open the XML data store and read the employee records. You will learn about XML in Chapter 17,“Interacting with a Microsoft Word Document and Event Viewer.” The .NET Framework class library provides you with the XmlTextReader class that helps you access a stream of XML data in a fast and noncached manner. I will be using the XmlTextReader class to read the EmpRec.xml file. You have created the EmpRec.xml file in Chapter 13, “Project Case Study and Design.”

The XmlTextReader represents a reader that is advanced using the read methods and properties of the current node. Table 14-2 lists some of the commonly used properties of the XmlTextReader class.

Table 14-2 Properties of the XmlTextReader Class

314 Project 2 CREATING THE EMPLOYEE RECORDS SYSTEM PROJECT

Table 14-3 lists some of the commonly used properties of the XmlTextReader class.

Table 14-3 Methods of the XmlTextReader Class

Now you need to read the employee codes from the EmpRec.xml file and display them in the tree view control.

You can open the XML file by initializing the XMLTextReader class, as follows:

XmlTextReader reader= new XmlTextReader (“E:\\BookProj\\EmpRec.xml”);

where e:\BookProj\EmpRec.xml represents the path on your hard disk where the EmpRec.xml file is stored.

I have written the entire code for populating the TreeView control inside a function, PopulateTreeView, as given below.

protected void PopulateTreeView()

{

statusBarPanel1.Text=”Refreshing Employee Codes. Please wait...”; this.Cursor = Cursors.WaitCursor;

treeView1.Nodes.Clear();

tvRootNode=new TreeNode(“Employee Records”); this.Cursor = Cursors.Default; treeView1.Nodes.Add(tvRootNode);

TreeNodeCollection nodeCollect = tvRootNode.Nodes; string strVal=””;

XmlTextReader reader= new XmlTextReader(“E:\\BookProj\\EmpRec.xml”);

reader.MoveToElement(); 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);

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)