GUI Windows Form C#

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
public class Form1 : Form
{
      private System.Windows.Forms.ListBox displayListBox;
      private System.Windows.Forms.TextBox inputTextBox;
      private System.Windows.Forms.Button addButton;
      private System.Windows.Forms.Button removeButton;
      private System.Windows.Forms.Button clearButton;
      
      public Form1() {
        InitializeComponent();
    }
      private void addButton_Click( object sender, EventArgs e )
      {
        displayListBox.Items.Add( inputTextBox.Text );
        inputTextBox.Clear();
      } 
      private void removeButton_Click( object sender, EventArgs e )
      {
        if ( displayListBox.SelectedIndex != -1 )
          displayListBox.Items.RemoveAt( displayListBox.SelectedIndex );
      }
      private void clearButton_Click( object sender, EventArgs e )
      {
         displayListBox.Items.Clear();
      }
      private void InitializeComponent()
      {
         this.displayListBox = new System.Windows.Forms.ListBox();
         this.inputTextBox = new System.Windows.Forms.TextBox();
         this.addButton = new System.Windows.Forms.Button();
         this.removeButton = new System.Windows.Forms.Button();
         this.clearButton = new System.Windows.Forms.Button();
         this.SuspendLayout();
         // 
         // displayListBox
         // 
         this.displayListBox.FormattingEnabled = true;
         this.displayListBox.Location = new System.Drawing.Point(13, 12);
         this.displayListBox.Name = "displayListBox";
         this.displayListBox.Size = new System.Drawing.Size(119, 238);
         this.displayListBox.TabIndex = 0;
         // 
         // inputTextBox
         // 
         this.inputTextBox.Location = new System.Drawing.Point(149, 12);
         this.inputTextBox.Name = "inputTextBox";
         this.inputTextBox.Size = new System.Drawing.Size(100, 20);
         this.inputTextBox.TabIndex = 1;
         // 
         // addButton
         // 
         this.addButton.Location = new System.Drawing.Point(149, 56);
         this.addButton.Name = "addButton";
         this.addButton.Size = new System.Drawing.Size(100, 36);
         this.addButton.TabIndex = 2;
         this.addButton.Text = "Add";
         this.addButton.Click += new System.EventHandler(this.addButton_Click);
         // 
         // removeButton
         // 
         this.removeButton.Location = new System.Drawing.Point(149, 109);
         this.removeButton.Name = "removeButton";
         this.removeButton.Size = new System.Drawing.Size(100, 36);
         this.removeButton.TabIndex = 3;
         this.removeButton.Text = "Remove";
         this.removeButton.Click += new System.EventHandler(this.removeButton_Click);
         // 
         // clearButton
         // 
         this.clearButton.Location = new System.Drawing.Point(149, 165);
         this.clearButton.Name = "clearButton";
         this.clearButton.Size = new System.Drawing.Size(100, 36);
         this.clearButton.TabIndex = 4;
         this.clearButton.Text = "Clear";
         this.clearButton.Click += new System.EventHandler(this.clearButton_Click);
         // ListBoxTestForm
         // 
         this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 13F);
         this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
         this.ClientSize = new System.Drawing.Size(263, 268);
         this.Controls.Add(this.clearButton);
         this.Controls.Add(this.removeButton);
         this.Controls.Add(this.addButton);
         this.Controls.Add(this.inputTextBox);
         this.Controls.Add(this.displayListBox);
         this.Name = "ListBoxTestForm";
         this.Text = "ListBoxTest";
         this.ResumeLayout(false);
         this.PerformLayout();
      }
      [STAThread]
      static void Main()
      {
    Application.EnableVisualStyles();
    Application.Run(new Form1());
    }
}