title: How to add dll in c# project
body: <p>I am trying to add a <strong>[Science.dll]</strong> in my project which should be straight forward. But I am getting a problem. Can someone tell me why?</p>
  <p>My C# project which I just copied from internet.</p>
  <pre><code>using System;
  using System.Collections.Generic;
  using System.Linq;
  using System.Windows.Forms;
  using System.ComponentModel;
  using System.Data;
  using Science.Mathematics.VectorCalculus;
  
  namespace using_science_dll
  {
      static class Program
      {
          /// &lt;summary&gt;
          /// The main entry point for the application.
          /// &lt;/summary&gt;`enter code here`
      }
  }
  </code></pre>
  <blockquote>
  <p>C:\Csharptutorial\using_science_dll\using_science_dll\Program.cs(7,7): error CS0246: The type or namespace name 'Science' could not be found (are you missing a using directive or an assembly reference?)</p>
  </blockquote>
  <p>Is it because I am using VS 2008?</p>
  <p><code>Science.dll</code> will run in the following frame .Net 4.0 and Visual C# 2010 Express</p>
  <p><img src="https://i.stack.imgur.com/hrP4o.png" alt="enter image description here" /></p>