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Displaying Simple MessageBox

About the sample application This application has 1 textbox and a button. If you type anything in the

textbox and press the button, it will display the same text you typed in a MessageBox.

Download and unzip the sample application from this page. After you unzip, you will get several files.

Some of the important files are :

1. Chapter1.csproj - This is the C# project file. Double click this file to

open the project.

2. Form1.cs - This is the file for the Form1 in teh sample application.

After you open the project, see the 'Solution Explorer' bar on the right side of the Visual Studio. You

can click on that to expand it, which will display the list of all files in the project. (Or, you can go to

the menu 'View > Solution Explorer' to open the solution explorer.

Click on 'Form1.cs' in the solution explorer to open the Form. Now you can see the Form in 'design

mode'. Right click on the 'Form1.cs' in the solution explorer and choose 'View Code' to see the source

code behind this Form (Or, press F7 from the Form to see the code).

Let us analyze the code:

The code has lot of Visual Studio generated code. For timebeing ignore all those code and scroll down

to the event handler code in the bottom of the file.

System.Windows.Forms.MessageBox.Show( "You typed : " +

txtMessage.Text );

DialogResult result = MessageBox.Show( "Did you like this

application ?",

"Caption", MessageBoxButtons.YesNo,

MessageBoxIcon.Question );

if ( result == DialogResult.Yes )

MessageBox.Show("You selected YES");

elseMessageBox.Show("You selected NO");

The first line will simply display a messagebox and show the text typed by the user. 'MessageBox' is a

class inside the namespace 'System.Windows.Forms'. We have a statement 'using

System.Windows.Forms' on top of the source code. This is like a source code. This will help us avoid

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typing 'System.Windows.Forms.' everytime when we want to use a class inside this namespace.

The next few lines of code do a bit more. Here we are displaying a message box, with some additional

attributes.

The second optional parameter of the 'Show' method is the 'caption' for the messagebox.

The third parameter tells that the messagebox will have two buttons - YES and NO. You have several

other options like MessageBoxButtons.OK, MessageBoxButtons.OKCancel etc.

And, the last parameter says 'display a question Icon in the messagebox'. There are many other

types of icons you can display.

And another important part is, the MessageBox returns a value when the user press a button to close

the messagebox. Our MessageBox asks a question 'Did you like this application ?" and gives two

options to the user - YES or NO.

The return value is of type 'DialogResult' and is assigned to the variable 'result'. We are checking the

value of the result and depending on whether user pressed the YES button or NO button, appropriate

message will be displayed.

Application Configuration Files

.NET gives an easy way to store configuration information in a ApplicationConfiguration File. In the

simple implementation, you can store information as Key-Value pairs.

For example, consider a case where you have to use a DataSource in your application. If you hardcore

the DataSource information in your code, you will have a bad time when you have to change this

datasource. You have to change your source code and re-compile it. This won't work everytime you

give your product to different customers or when you run your application in different machines!

In earlier days, programmers used to store this information in special files called ".ini" files or in

system registry. The application can read the information from the .ini file or registry and no need to

re-compile the code when the values are changed in .ini file or registry.

But this is a pain most of the time. It is not fun opening the registry, locate your entries and make

appropriate changes. It is quite possible that you may mess up with some important entries in the

registry and make your system not running any more. In fact, in secured systems, administrator may

deny access to the registry and users will not have the choice to edit the registry at all.

.NET gives you a simple and easy solution for this problem - theApplicationConfiguration File. Each

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application can have a configuration file, which is actually an XML file. You can use any text editor

(including notepad) to open the configuration file and change the values. The application will load the

values from this configuration file and you do not have to change your source code everytime you

change your DataSource or any other information stored in configuration file.

app.config for Windows applications

Windows applications in VS.NET uses the name 'app.config' by default for the configuration file. This

will not be automatically created when you create a Windows application. If you need a configuration

file for your application, open your project in VS.NET, go to the 'Solution Explorer' and right click on

the project name. Choose Add > Add new item from the menu and select 'Application Configuration

file' from the list of choices. This will create an app.config file for you in the application root.

By default, the app.config file will have the following content:

To store values in configuration file, you can create xml elements in theformat

See the sample config entries below:

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And to read from this config file, just use the following code in your application:

string dbPath =

System.Configuration.ConfigurationSettings.AppSettings["D

atabasePath"];

string email =

System.Configuration.ConfigurationSettings.AppSettings["S

upportEmail"];

ConfigurationSettings is the class

used to access the contents of the configuration file. Since this class is part

of the namespace System.Configuration,we have to use the fully qualified

name System.Configuration.ConfigurationSettings.

As a shortcut, you can use the using directive

on top of the file like below:

using System.Configuration;

If you have the above directive on top of the file, then you can directly use

the class ConfigurationSettings.

string dbPath =

ConfigurationSettings.AppSettings["DatabasePath"];

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string email =

ConfigurationSettings.AppSettings["SupportEmail"];

In VB.NET, you have to use "( ... )" instead of the "[ ... ]", as shown below:

Dim dbPath as String =

ConfigurationSettings.AppSettings("DatabasePath")

Dim email as String =

ConfigurationSettings.AppSettings("SupportEmail")