The type or namespace name 'Linq' does not exist in the namespace 'System'
<p>When I want to use button to write code in C# it doesn't go to the &quot;.cs&quot; file to write C# code. When I check the project source, I found this error:</p>
<pre><code>using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
</code></pre>
<blockquote>
<p>Severity  Code    Description Project File    Line Error  CS0234  The type or
namespace name 'Linq' does not exist in the namespace 'System' (are
you missing an assembly reference?)   Golestani C:\Users\javad\Documents\Golestani\Login.aspx.cs 3</p>
</blockquote>
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