title: How can I call a method in a class from a WinForm?
body: <p>I'm new to winforms and a beginner in c#. I created a simple application using else if. The user is to enter a value between 0 and 10 and press a button. If the number is between that range, a messagebox pops giving a message along with the number entered. But if the number is higher than 10, a messagebox pops saying "The number must be below 10". So far I got all this working but now I would like to have class handling the logic behind it but I don't know how to make the class1.cs and the Form1.cs to access each other's info.  To my understanding, Class1.cs is to get the value entered from Form1, analyze it and return a value. Then Form1.cs is to take that returned value and display it -am I right?-. But i don't know how to do this.</p>
  
  <p>What I'm asking here basically is if you could show me what do I have to put into my class1.cs  so it will do the if/else logic within itself <strong>instead</strong> of doing it in Form1.cs (the way it's now).</p>
  
  <p>Thank you guys !</p>
  
  <p><strong>Form1.cs</strong></p>
  
  <pre><code>using System.Collections.Generic;
  using System.ComponentModel;
  using System.Data;
  using System.Drawing;
  using System.Linq;
  using System.Text;
  using System.Windows.Forms;
  
  namespace WindowsFormsApplication2
  {
      public partial class Form1 : Form
      {
          public Form1()
          {
              InitializeComponent();
          }
  
          private void label1_Click(object sender, EventArgs e)
          {
  
          }
  
          private void btnDone_Click(object sender, EventArgs e)
          {
  
              double number = Convert.ToDouble(txtNumber.Text);
  
              if (number &gt; 10)
              {
                  MessageBox.Show("Number must be below 10");
  
              }
              else {
                  MessageBox.Show("Good !  You entered : " + number);
              }
          }
      }
  }
  </code></pre>
  
  <p><strong>Class1.cs</strong></p>
  
  <pre><code>using System;
  using System.Collections.Generic;
  using System.Linq;
  using System.Text;
  
  namespace WindowsFormsApplication2
  {
      class Class1
      {
  
      }
  }
  </code></pre>