title: Namespace '<global namespace>' contains a definition conflicting with alias 'PersianDate'
body: <p>I'm developing a <code>winform</code> application in C# and everything was fine. But all of a sudden I get this weird error when I tried to run the application.</p>
  
  <blockquote>
    <p>Namespace '' contains a definition conflicting with alias 'PersianDate'</p>
  </blockquote>
  
  <p>This is the line which throws the error.</p>
  
  <pre><code>private PersianDate _quotationDate;
  </code></pre>
  
  <p>All I done before getting the error was to add this <code>form_load</code> event.</p>
  
  <pre><code>private void frmAddDragSource_Load(object sender, EventArgs e)
   {
     this.Text = "Source";
   }
  </code></pre>
  
  <p>Does anyone knows why this happens and how can I fix it?</p>
  
  <p><strong>UPDATE</strong> 
  my usings:</p>
  
  <pre><code>using System;
  using System.Collections.Generic;
  using System.ComponentModel;
  using System.Data;
  using System.Data.SqlServerCe;
  using System.Drawing;
  using System.Linq;
  using System.Text;
  using System.Windows.Forms;
  using FishTablighPro.Utility;
  using PersianDate = FreeControls.PersianDate;
  </code></pre>