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

namespace WindowsApplication1
{
	/// <summary>
	/// Summary description for Form1.
	/// </summary>
	public class Form1 : System.Windows.Forms.Form
	{
		private System.Windows.Forms.Button button1;
		private System.Windows.Forms.Label label1;
		private System.Windows.Forms.Button button2;
		private System.Windows.Forms.RichTextBox richTextBox1;
		private System.Windows.Forms.RichTextBox richTextBox2;
		/// <summary>
		/// Required designer variable.
		/// </summary>
		private System.ComponentModel.Container components = null;
		
		public Form1()
		{
			//
			// Required for Windows Form Designer support
			//
			InitializeComponent();

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

		/// <summary>
		/// Clean up any resources being used.
		/// </summary>
		protected override void Dispose( bool disposing )
		{
			if( disposing )
			{
				if (components != null) 
				{
					components.Dispose();
				}
			}
			base.Dispose( disposing );
		}

		#region Windows Form Designer generated code
		/// <summary>
		/// Required method for Designer support - do not modify
		/// the contents of this method with the code editor.
		/// </summary>
		private void InitializeComponent()
		{
			this.richTextBox2 = new System.Windows.Forms.RichTextBox();
			this.label1 = new System.Windows.Forms.Label();
			this.button1 = new System.Windows.Forms.Button();
			this.button2 = new System.Windows.Forms.Button();
			this.richTextBox1 = new System.Windows.Forms.RichTextBox();
			this.SuspendLayout();
			// 
			// richTextBox2
			// 
			this.richTextBox2.Location = new System.Drawing.Point(240, 128);
			this.richTextBox2.Name = "richTextBox2";
			this.richTextBox2.Size = new System.Drawing.Size(176, 32);
			this.richTextBox2.TabIndex = 5;
			this.richTextBox2.Text = "5048480100296497";
			// 
			// label1
			// 
			this.label1.BackColor = System.Drawing.Color.SlateGray;
			this.label1.Font = new System.Drawing.Font("Microsoft Sans Serif", 9.75F, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, ((System.Byte)(0)));
			this.label1.Location = new System.Drawing.Point(24, 128);
			this.label1.Name = "label1";
			this.label1.Size = new System.Drawing.Size(176, 32);
			this.label1.TabIndex = 2;
			this.label1.Text = "Enter your 16/15 digits credit card number";
			// 
			// button1
			// 
			this.button1.BackColor = System.Drawing.Color.LightSlateGray;
			this.button1.Location = new System.Drawing.Point(80, 208);
			this.button1.Name = "button1";
			this.button1.Size = new System.Drawing.Size(120, 32);
			this.button1.TabIndex = 1;
			this.button1.Text = "Check";
			this.button1.Click += new System.EventHandler(this.button1_Click);
			// 
			// button2
			// 
			this.button2.BackColor = System.Drawing.Color.SlateGray;
			this.button2.Location = new System.Drawing.Point(232, 208);
			this.button2.Name = "button2";
			this.button2.Size = new System.Drawing.Size(120, 32);
			this.button2.TabIndex = 3;
			this.button2.Text = "&Exit";
			this.button2.Click += new System.EventHandler(this.button2_Click);
			// 
			// richTextBox1
			// 
			this.richTextBox1.Font = new System.Drawing.Font("Microsoft Sans Serif", 12F, System.Drawing.FontStyle.Regular, System.Drawing.GraphicsUnit.Point, ((System.Byte)(0)));
			this.richTextBox1.Location = new System.Drawing.Point(16, 312);
			this.richTextBox1.Name = "richTextBox1";
			this.richTextBox1.Size = new System.Drawing.Size(472, 104);
			this.richTextBox1.TabIndex = 4;
			this.richTextBox1.Text = "Enter Your Credit Card number and press Check button";
			
			// 
			// Form1
			// 
			this.AutoScaleBaseSize = new System.Drawing.Size(5, 13);
			this.BackColor = System.Drawing.Color.MidnightBlue;
			this.ClientSize = new System.Drawing.Size(504, 517);
			this.Controls.AddRange(new System.Windows.Forms.Control[] {
																		  this.richTextBox2,
																		  this.richTextBox1,
																		  this.button2,
																		  this.label1,
																		  this.button1});
			this.Name = "Form1";
			this.Text = "Credit Card Check Digit";
			this.ResumeLayout(false);

		}
		#endregion

		/// <summary>
		/// The main entry point for the application.
		/// </summary>
		[STAThread]
		static void Main() 
		{
			Application.Run(new Form1());
			//		Console.WriteLine("raju : ");
		}

		
		private void button1_Click(object sender, System.EventArgs e)
		{	
			int[] intNumber = new int[16]; 
			int[] arr = new int[16];
			int[] arr1 = new int[16];
			int[] sum = new int[16];
			int k =0;
			
			string cardno = richTextBox2.Text;
			for(int i=0;i<=15;i++)
				intNumber[i]=-1;
			char[] myChars = cardno.ToCharArray(); 
			for(int i=0;i<=myChars.Length-1;i++)
			{
			
				intNumber[i] = (System.Convert.ToInt32(myChars[i])-48);
			
			}
			
			
       // For 16 Digit Credit Card Number
			
			if(intNumber[15]!= -1)
			{

			// placing 1's in even places
				for(int j=1;j<=15;)
				{
					arr[j]=1;
					j=j+2;
				
				}
				// placing 2's in odd places
				for(int j=0;j<=15;)
				{
					arr[j]=2;
					j=j+2;
				
				}
				
				sum[0]=0;
			
				for(k=0;k<=15;k++)
				{
					
					arr1[k]=((intNumber[k]*arr[k]));
					// Substract 9 if the product is greater than 9
					if(arr1[k]>9)
						arr1[k]= (arr1[k]-9);
					else
						arr1[k]=arr1[k];
					
					// Find Sum of all elements				
					if(k==0)
					{
						sum[k]=arr1[k];
					}
					
					if(k!=0)
					{
						sum[k]=sum[k-1]+arr1[k];
					}
					// finding mod 
					if(sum[k]%10==0)
					{
						richTextBox1.Text= "Congrats!! The Credit Card Number You Entered is Correct";
					}
					else richTextBox1.Text="Sorry,Please Check Your Credit Card Number and Try Again";

				}// end of for			
					
			}// end of if
			// Similarly the code for 15 digit credit card
			if(intNumber[14]!= -1 && intNumber[15]== -1)
			{
				for(int j=1;j<=14;)
				{
					arr[j]=2;
					j=j+2;
				}
				for(int j=0;j<=14;)
				{
					arr[j]=1;
					j=j+2;
				}
				for(int j=0;j<=14;j++)
				
				sum[0]=0;
			
				for(k=0;k<=14;k++)
				{
				
					arr1[k]=((intNumber[k]*arr[k]));
					if(arr1[k]>9)
						arr1[k]= (arr1[k]-9);
					else
						arr1[k]=arr1[k];
						
					if(k==0)
					{
						sum[k]=arr1[k];
					}
					
					if(k!=0)
					{
						sum[k]=sum[k-1]+arr1[k];
					}
					
					if(sum[k]%10==0)
					{
						richTextBox1.Text= "Congrats!! The Credit Card Number You Entered is Correct";
					}
					else richTextBox1.Text="Sorry,Please Check Your Credit Card Number and Try Again";


				}// end of for			
                 
			}
		}
		
		private void button2_Click(object sender, System.EventArgs e)
		{
			Application.Exit();
		}

		
	}
}