Recursive Function: Factorial: Part 3: C# Application

Doing Factorial in C# for Windows Application

Here, an example is shown how to implement factorial code in C# for the Windows application.

First, you need to use Design to set up form like this (how to set up components, like button or text box, are not shown).

Recursion Class is shown below.

using System; using System.Collections.Generic; using System.Linq; using System.Text;   namespace Recursion {     class Factorial     {         public Factorial()         {         }         public int fact(int n)         {             if (n == 0)             {                 return 1;   //base case             }             else             {                 return n * fact(n - 1);             }         }     } }

The GUI part is shown below.

using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Linq; using System.Text; using System.Windows.Forms;   namespace Recursion {     public partial class txbFactInput : Form     {         public txbFactInput()         {             InitializeComponent();         }         private void button1_Click(object sender, EventArgs e)         {             //MessageBox.Show("testing");             //int n = Convert.ToInt16(txtb1.Text);               // Using TryParse, test if an integer was entered             int n;             if (int.TryParse(txtb1.Text, out n))             {                 // Integer was put in test box                 txtb1.Text = null;              //clear text box                 Factorial t = new Factorial();  //create Factorial object                 lblAnswer.Text = t.fact(n).ToString();  //answer here             }             else             {                 // Error                 lblAnswer.Text = "Error! Input an integer";             }         }     } }

The form in Windows Application