title: Why should you remove unnecessary C# using directives?
body: <p>For example, I rarely need:</p>
  
  <pre><code>using System.Text;
  </code></pre>
  
  <p>but it's always there by default. I assume the application will use more memory if your code contains unnecessary <a href="http://msdn.microsoft.com/en-us/library/aa664764(VS.71).aspx" rel="noreferrer">using directives</a>. But is there anything else I should be aware of?</p>
  
  <p>Also, does it make any difference whatsoever if the same using directive is used in only one file vs. most/all files?</p>
  
  <hr>
  
  <p><em>Edit: Note that this question is not about the unrelated concept called a <a href="http://msdn.microsoft.com/en-us/library/yh598w02.aspx" rel="noreferrer">using statement</a>, designed to help one manage resources by ensuring that when an object goes out of scope, its <a href="http://msdn.microsoft.com/en-us/library/system.idisposable.dispose.aspx" rel="noreferrer">IDisposable.Dispose</a> method is called. See <a href="https://stackoverflow.com/questions/75401/uses-of-using-in-c">Uses of "using" in C#</a>.</em></p>