title: How To Catch And Fix Project Error in ASP.NET Private API
body: <p>Before 1 year I create app on asp.NET Private API, Now I try to start but Every time when I try to see my data on JSON format the project give me error.</p>
  
  <pre><code>Server Error in '/' Application.
  Compilation Error
  Description: An error occurred during the compilation of a resource required to service this request. Please review the following specific error details and modify your source code appropriately.
  
  Compiler Error Message: CS0012: The type 'Dictionary&lt;,&gt;' is defined in an assembly that is not referenced. You must add a reference to assembly 'System.Collections, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'.
  
  Source Error:
  </code></pre>
  
  <p>View/Web.config</p>
  
  <pre><code> &lt;?xml version="1.0"?&gt;
  
  &lt;configuration&gt;
    &lt;configSections&gt;
      &lt;sectionGroup name="system.web.webPages.razor" type="System.Web.WebPages.Razor.Configuration.RazorWebSectionGroup, System.Web.WebPages.Razor, Version=3.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"&gt;
        &lt;section name="host" type="System.Web.WebPages.Razor.Configuration.HostSection, System.Web.WebPages.Razor, Version=3.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" requirePermission="false" /&gt;
        &lt;section name="pages" type="System.Web.WebPages.Razor.Configuration.RazorPagesSection, System.Web.WebPages.Razor, Version=3.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" requirePermission="false" /&gt;
      &lt;/sectionGroup&gt;
    &lt;/configSections&gt;
  
    &lt;system.web.webPages.razor&gt;
      &lt;host factoryType="System.Web.Mvc.MvcWebRazorHostFactory, System.Web.Mvc, Version=5.2.3.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" /&gt;
      &lt;pages pageBaseType="System.Web.Mvc.WebViewPage"&gt;
        &lt;namespaces&gt;
          &lt;add namespace="System.Web.Mvc" /&gt;
          &lt;add namespace="System.Web.Mvc.Ajax" /&gt;
          &lt;add namespace="System.Web.Mvc.Html" /&gt;
          &lt;add namespace="System.Web.Optimization"/&gt;
          &lt;add namespace="System.Web.Routing" /&gt;
          &lt;add namespace="Private_API" /&gt;
        &lt;/namespaces&gt;
      &lt;/pages&gt;
    &lt;/system.web.webPages.razor&gt;
  
    &lt;appSettings&gt;
      &lt;add key="webpages:Enabled" value="false" /&gt;
    &lt;/appSettings&gt;
  
    &lt;system.webServer&gt;
      &lt;handlers&gt;
        &lt;remove name="BlockViewHandler"/&gt;
        &lt;add name="BlockViewHandler" path="*" verb="*" preCondition="integratedMode" type="System.Web.HttpNotFoundHandler" /&gt;
      &lt;/handlers&gt;
    &lt;/system.webServer&gt;
  
    &lt;system.web&gt;
      &lt;compilation&gt;
        &lt;assemblies&gt;
          &lt;add assembly="System.Web.Mvc, Version=5.2.3.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" /&gt;
        &lt;/assemblies&gt;
      &lt;/compilation&gt;
    &lt;/system.web&gt;
  &lt;/configuration&gt;
  </code></pre>
  
  <p>Can you provide instructions on how to fix the error or directly instructions for the problem ?</p>