03 gui 04

GUI Applications Development Using .NET Framework
Objectives

In this session, you will learn to:
Validate user input using controls and events
Work with the CommonDialog class
Create a custom dialog box

Ver. 1.0 Session 4 Slide 1 of 25

Validation of User Inputs

Validation is a means to check the accuracy and
correctness of the data entered by a user in an application.
By performing validation, you can prompt the user to enter
correct data and therefore, reduce errors.
To validate data in a control, the Validating event of that
control can be used.
After performing validation, the user can be prompted by an
appropriate message.
This message can be displayed using:
MessageBox class
ErrorProvider Control
StatusStrip Control
Let us understand how the data in the controls can be
validated.


Just a minute

Name the event that enables the user to prevent shifting of
focus from a control until all the validation rules have been
met.

Answer:
The Validating event


The MessageBox Class

• The MessageBox class is used to display informative
messages to users.
• For example, the following code snippet displays a
message box on the click event of a button.
private void button1_Click(object
sender,EventArgs e)
{
MessageBox.Show("The entered data is not
valid. Please enter valid data.", "Data
Entry Error", MessageBoxButtons.OK,
MessageBoxIcon.Error);
}
Message Box Text


The MessageBox Class (Contd.)

messages to users.
sender,EventArgs e)
{
MessageBoxIcon.Error); Message Box Title
}



messages to users.
sender,EventArgs e)
{
}

Message Box Button



messages to users.
sender,EventArgs e)
{
}
Message Box Icon


Just a minute

• How many parameters are there in the Show() method of
the MessageBox class?
1. One
2. Two
3. Three
4. Four

Answer:
4. Four


Just a minute

• Which method of the MessageBox class is used to display
a message in the message box?

Answer:
– The Show() method


The StatusStrip Control

• The StatusStrip control is a container control derived from
System.Windows.Forms.ToolStrip class.
• This control is used to:
– Display information about the objects that are on the current
form.
– Provide feedback on the progress of any operation being
performed by the form.
A StatusStrip control contains four child controls. These
child controls are:
StatusLabel
ProgressBar
DropDownButton
SplitButton


The StatusStrip Control (Contd.)

The following figure shows the StatusStrip control with its
child controls.

This control is used to
display status information
This control is used to show
and prompt the user for a
This control displays
the completion status of any
valid entry.
ThisToolStripDropDown from
control is a
task.
combination user standard a
which a of a can select
button on the left andmany
single item from a
items.
dropdown button on the
right.


Just a minute

Which of the following position is the default docking
position of the StatusStrip control on the form?
1. Left
2. Right
3. Top
4. Bottom

Answer:
4. Bottom


Just a minute

Which property of the ProgressBar control specifies the
amount to increment the current value of the control?
1. Minimum
2. Maximum
3. Value
4. Step

Answer:
4. Step


The ErrorProvider Control

The ErrorProvider control can be used to display an error
message, whenever the user positions the mouse pointer
over the error icon.
This error icon is displayed next to the control in which the
user has entered invalid data.
The following figure displays an ErrorProvider control
attached to a text box on the form.

ErrorProvider
Control


Just a minute

Which property of the ErrorProvider control automatically
sets to the form to which it is added?
1. SetError
2. ContainerControl
3. Error on errorProviderControlName
4. BlinkStyle

Answer:
2. ContainerControl


Demo: Validating Data

Problem Statement:
SigmaCom is a telecommunication company which is
developing software that would gather information about its
employees. The company requires that the information entered
should be correct and all the fields should be filled with
required data and that no fields are left blank.
Help the company to develop the required application.


Demo: Validating Data (Contd.)

Solution:
To meet the preceding requirement, you need to perform the
following tasks:
1. Create a new VC# application.
2. Design the Employee Information form.
3. Add code to perform the desired tasks.
4. Execute the application and verify the output.


Introducing CommonDialog Classes

• In VC#, the CommonDialog class is the base class for
displaying common dialog boxes such as font dialog box,
open dialog box, and save dialog box.


Types of CommonDialog Classes

• There are various classes that are inherited from the
CommonDialog class. These are:
ColorDialog class
FontDialog class
FileDialog class
OpenFileDialog class
SaveFileDialog class
FolderBrowserDialog class
PrintDialog class
Let us understand how these dialog boxes work.


Creating Custom Dialog Box

In VC#, the user can create customized dialog boxes in
order to perform some specific tasks.
The Windows Forms Designer can be used for creating a
custom dialog box with the following changes:
– Assign a value of FixedDialog to the FormBorderStyle
property of the form.
– Assign a value of False to the ControlBox, MinimizeBox,
and MaximizeBox properties of the form.
– Assign an appropriate value to the DialogResult property
for each button used on the form.


Just a minute

All the classes that inherit from the CommonDialog class
override the ___________ method to create a specific
dialog box.

Answer:
RunDialog()


Demo: Creating Custom Dialog Box

Problem Statement:
Create an application that would accept the user input into a
rich text box control. The application should have a Zoom
button. This button should invoke a custom dialog box, which
should accept a numeric value from a user. Whatever value is
passed through the dialog box, the text in the rich text box
control should get enlarged by that percentage.


Demo: Creating Custom Dialog Box (Contd.)

Solution:
To create the application, you need to perform the following
tasks:
1. Create a new VC# application.
2. Design the main form.
3. Design a custom dialog box.
4. Add code in the custom dialog box.
5. Add code in the main form.
6. Execute the application and verify the output.


Summary

In this session, you learned that:
– Validation is a means to check the accuracy and the
correctness of the data entered by the user.
– The Validating event enables you to prevent the user from
shifting the focus from the control being validated to some
other control on the form until all validation rules have been
met.
– The MessageBox class is used to display prompts and
messages on the screen. After closing the message box the
user cannot see the message.
– An instance of the MessageBox class cannot be created by
using the new keyword.
– The StatusStrip control is derived from
System.Windows.Forms.ToolStrip class. It is a container
control that can hold other controls.


Summary (Contd.)

The StatusStrip control contains four types of controls. The
controls are:
• StatusLabel
• ProgressBar
• DropDownButton
• SplitButton
– The ErrorProvider control is used to display an error message,
whenever the user positions the mouse pointer over the error
icon.
– The CommonDialog class is the base class for the most
commonly used dialog boxes, such as, Color, Font, File,
FolderBrowser, Print, and Page Setup.
– A Custom dialog box can be created by setting some
properties of the Windows Form such as, FormBorderStyle,
ControlBox, MinimizeBox, and MaximizeBox.


03 gui 04

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