title: the call is ambiguous between the same methods Asp.Net C#
body: <p>I tried to edit a GridView in one of the pages of my site, topics.aspx. I decided to change the DataSourceID, from the one I put in design view on the grid view, with a custom one, following this tutorial</p>
  
  <p><a href="http://www.c-sharpcorner.com/uploadfile/9f0ae2/gridview-edit-delete-and-update-in-asp-net/?authorFollow=true-9f0ae2-article&amp;name=neha-sharma52" rel="nofollow noreferrer">http://www.c-sharpcorner.com/uploadfile/9f0ae2/gridview-edit-delete-and-update-in-asp-net/?authorFollow=true-9f0ae2-article&amp;name=neha-sharma52</a></p>
  
  <p>I COPIED and PASTED the exact SqlConnection from the register.aspx.cs page, which is</p>
  
  <pre><code>SqlConnection conn = new SqlConnection(ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString);
  </code></pre>
  
  <p>as a private field in topic.aspx.cs.</p>
  
  <p>Suddenly, my register page doesn't work anymore. The "SqlConnection" in</p>
  
  <pre><code>new SqlConnection(...)
  </code></pre>
  
  <p>call is "ambigous" between</p>
  
  <pre><code>SqlConnection.SqlConnection(string)
  </code></pre>
  
  <p>and</p>
  
  <pre><code>SqlConnection.SqlConnection(string)
  </code></pre>
  
  <p>I undid everything I did, obviously. My last resort is to delete topics.aspx and topics.aspx.cs altogether, but... will it work then? I highly doubt did.</p>
  
  <p>I don't know what i did wrong, I only copied and pasted a line of code, and suddenly, my register.aspx and login.aspx don't work anymore. What is the problem?</p>
  
  <p>EDIT:
  The imports I am using are</p>
  
  <pre><code>using System;
  using System.Collections.Generic;
  using System.Configuration;
  using System.Data.SqlClient;
  using System.Linq;
  using System.Web;
  using System.Web.UI;
  using System.Web.UI.WebControls;
  </code></pre>