The "/t:library" in compilation code says that c# compiler to create a library and also tells to not to look for a static Main() method.

The code is fairly simple. We create one Class Account with three methods checkBalance(), Deposite() and WithDraw(). My Initial Balance is 100;

If you want to create dll component using VS.NET IDE create new C# ClassLibrary from New Project Wizard. It will automatically create the .dll in your debug folder of the proect's folder.

Our DLL component is complete now. Lets call this component in our another csharp application.
Call methods and properties of the dll from a C# client is also an easy task. Just follow these few simple steps and see how to use component in C#.
Now start the C# Windows application.
Add Reference of the Namespace
Go to Projects menu and Add reference. Browse your dll component. And click OK.

Now you can use your Component in your application.

Use namespace using BankAccount;

Now you have to create an Object of BankAccount.Account.

Account sachinac = new BankAccount.Account();

Now call the Methods and properties.
Make one Form with one TextBox and three Buttons.

Control     Name
*******         *****
TextBox      Amount
CommandButton  CheckBalance
CommandButton  Deposite
CommandButton  WithDraw

Now double click on CheckBalance Button and write the code.

MessageBox.Show("Your Balance is " + sachinAc.Balance);

We will keep our coding simple, So we can understand how to use object. Repeat same thing for other buttons.

For Deposite Button :
sachinAc.Deposite(Convert.ToInt32(Amount.Text));

For WithDraw Button :
sachinAc.WithDraw(Convert.ToInt32(Amount.Text));

Now compile your Application. And Check everything is going perfect.

Here we used Convert.ToInt32 to convert String object into Int, because Amount.Text is String and We have defined method parameter amt as int.

Check Balance will show you the current balance. Enter some amount in TextBox and click on any of the button then check your current balance.

Great, So we have just created on component, basic simple but it is a component. C# provides full supports for properties, Events, Interfaces for components.

We will take a detailed look about interfaces and events in the next week with one big example. And will explore some more about CLS. Also we will see how to use C# component in VB.NET.

Versioning

Your component no longer need to be registered with the registry. Here, a developer can guarantee that his component will retain binary compatibility with existing client applications, as you can use different versions of a library in the same context because the libraries are referenced not by the Registry, but by the metadata contained in the executable code.

Regards

Code Listing 1.0

using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;
using System.Data;
using BankAccount;


namespace SachinAccount
{
  public class Form1 : System.Windows.Forms.Form
  {
    private System.Windows.Forms.Button button1;
    Account sachinAc = new  Account();
    private System.Windows.Forms.Button button2;
    private System.Windows.Forms.Button button3;
    public System.Windows.Forms.TextBox Amount;
    
    private System.ComponentModel.Container components = null;

    public Form1()
    {
      InitializeComponent();
      

      //
      // TODO: Add any constructor code after InitializeComponent 
call
      //
    }

    /// 

    /// Clean up any resources being used.
    /// 
    protected override void Dispose( bool disposing )
    {
      if( disposing )
      {
        if (components != null) 
        {
          components.Dispose();
        }
      }
      base.Dispose( disposing );
    }
    
    public void InitializeComponent()
    {
      this.button1 = new System.Windows.Forms.Button();
      this.button2 = new System.Windows.Forms.Button();
      this.button3 = new System.Windows.Forms.Button();
      this.Amount = new System.Windows.Forms.TextBox();
      this.SuspendLayout();
       
      this.button1.Font = new System.Drawing.Font("Trebuchet MS", 
8.25F, System.Drawing.FontStyle.Bold, System.Drawing.GraphicsUnit.Point, 
((System.Byte)(0)));
      this.button1.Location = new System.Drawing.Point(8, 120);
      this.button1.Name = "button1";
      this.button1.Size = new System.Drawing.Size(96, 24);
      this.button1.TabIndex = 0;
      this.button1.Text = "Check Balance";
      this.button1.Click += new 
System.EventHandler(this.button1_Click);
      // 
      // button2
      // 
      this.button2.Font = new System.Drawing.Font("Trebuchet MS", 
8.25F, System.Drawing.FontStyle.Bold, System.Drawing.GraphicsUnit.Point, 
((System.Byte)(0)));
      this.button2.Location = new System.Drawing.Point(120, 120);
      this.button2.Name = "button2";
      this.button2.Size = new System.Drawing.Size(96, 24);
      this.button2.TabIndex = 0;
      this.button2.Text = "Deposite";
      this.button2.Click += new 
System.EventHandler(this.button2_Click);
      // 
      // button3
      // 
      this.button3.Font = new System.Drawing.Font("Trebuchet MS", 
8.25F, System.Drawing.FontStyle.Bold, System.Drawing.GraphicsUnit.Point, 
((System.Byte)(0)));
      this.button3.Location = new System.Drawing.Point(232, 120);
      this.button3.Name = "button3";
      this.button3.Size = new System.Drawing.Size(96, 24);
      this.button3.TabIndex = 2;
      this.button3.Text = "WithDraw";
      this.button3.Click += new 
System.EventHandler(this.button3_Click);
       
      this.Amount.Font = new System.Drawing.Font("Trebuchet MS", 
8.25F, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, 
((System.Byte)(0)));
      this.Amount.Location = new System.Drawing.Point(72, 48);
      this.Amount.Name = "Amount";
      this.Amount.Size = new System.Drawing.Size(192, 20);
      this.Amount.TabIndex = 3;
      this.Amount.Text = "Enter your Amount";
       
      this.AutoScaleBaseSize = new System.Drawing.Size(5, 13);
      this.ClientSize = new System.Drawing.Size(336, 157);
      this.Controls.AddRange(new System.Windows.Forms.Control[] {
                          
            this.Amount,
                          
            this.button3,
                          
            this.button2,
                          
            this.button1});
      this.Name = "Form1";
      this.Text = "Form1";
      
      this.ResumeLayout(false);

    }
    
    [STAThread]
    static void Main() 
    {
      Application.Run(new Form1());
    }

    private void button1_Click(object sender, System.EventArgs e)
    {
      
      
      MessageBox.Show("Your Balance is " + sachinAc.Balance);

    }

    private void button2_Click(object sender, System.EventArgs e)
    {
      
      sachinAc.Deposite(Convert.ToInt32(Amount.Text));
      
    }

    private void button3_Click(object sender, System.EventArgs e)
    {
      sachinAc.WithDraw(Convert.ToInt32(Amount.Text));
    }  
  }
}