title: ASP.NET Web Api HttpResponseException 400 (Bad Request) Hijacked by IIS
body: <p>I'm writing a Web API service and trying to return a (400) Bad Request if my ModelState is invalid. I do not want a response body to be attached to this. It appears that IIS is hijacking my response and always returning a text/html content type with a lengthy, styled error page. This is a problem.</p>
  
  <pre><code>    [HttpPost]
      public void Link(LinkDeviceModel model)
      {
  
          if (ModelState.IsValid)
          {
              try
              {
                  model.Save();
              }
              catch (Exception ex)
              {
                  ErrorSignal.FromCurrentContext().Raise(ex);
                  throw new HttpResponseException(ex.Message, HttpStatusCode.InternalServerError);
              }
          }
          else
          {
              throw new HttpResponseException(HttpStatusCode.BadRequest);
          }
      }
  </code></pre>
  
  <p>Here is my fiddler request:</p>
  
  <pre><code>POST http://localhost/myapp/service/link HTTP/1.1
  Host: localhost
  Content-Length: 112
  Content-Type: application/json
  Accept: application/json
  
  {"DeviceUniqueId":"CC9C6FC0-7D06-11E1-8B0E-31564824019B", "UserName": "me@mycompany.com"," Pin": "111111"}
  </code></pre>
  
  <p>And my response erroneous, full of body, response:</p>
  
  <pre><code>    &lt;!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"&gt; 
  &lt;html xmlns="http://www.w3.org/1999/xhtml"&gt; 
  &lt;head&gt; 
  &lt;title&gt;IIS 7.5 Detailed Error - 400.0 - Bad Request&lt;/title&gt; 
  &lt;style type="text/css"&gt; 
  &lt;!-- 
  body{margin:0;font-size:.7em;font-family:Verdana,Arial,Helvetica,sans-serif;background:#CBE1EF;} 
  code{margin:0;color:#006600;font-size:1.1em;font-weight:bold;} 
  .config_source code{font-size:.8em;color:#000000;} 
  pre{margin:0;font-size:1.4em;word-wrap:break-word;} 
  ul,ol{margin:10px 0 10px 40px;} 
  ul.first,ol.first{margin-top:5px;} 
  fieldset{padding:0 15px 10px 15px;} 
  .summary-container fieldset{padding-bottom:5px;margin-top:4px;} 
  legend.no-expand-all{padding:2px 15px 4px 10px;margin:0 0 0 -12px;} 
  legend{color:#333333;padding:4px 15px 4px 10px;margin:4px 0 8px -12px;_margin-top:0px; 
   border-top:1px solid #EDEDED;border-left:1px solid #EDEDED;border-right:1px solid #969696; 
   border-bottom:1px solid #969696;background:#E7ECF0;font-weight:bold;font-size:1em;} 
  a:link,a:visited{color:#007EFF;font-weight:bold;} 
  a:hover{text-decoration:none;} 
  h1{font-size:2.4em;margin:0;color:#FFF;} 
  h2{font-size:1.7em;margin:0;color:#CC0000;} 
  h3{font-size:1.4em;margin:10px 0 0 0;color:#CC0000;} 
  h4{font-size:1.2em;margin:10px 0 5px 0; 
  }#header{width:96%;margin:0 0 0 0;padding:6px 2% 6px 2%;font-family:"trebuchet MS",Verdana,sans-serif; 
   color:#FFF;background-color:#5C87B2; 
  }#content{margin:0 0 0 2%;position:relative;} 
  .summary-container,.content-container{background:#FFF;width:96%;margin-top:8px;padding:10px;position:relative;} 
  .config_source{background:#fff5c4;} 
  .content-container p{margin:0 0 10px 0; 
  }#details-left{width:35%;float:left;margin-right:2%; 
  }#details-right{width:63%;float:left;overflow:hidden; 
  }#server_version{width:96%;_height:1px;min-height:1px;margin:0 0 5px 0;padding:11px 2% 8px 2%;color:#FFFFFF; 
   background-color:#5A7FA5;border-bottom:1px solid #C1CFDD;border-top:1px solid #4A6C8E;font-weight:normal; 
   font-size:1em;color:#FFF;text-align:right; 
  }#server_version p{margin:5px 0;} 
  table{margin:4px 0 4px 0;width:100%;border:none;} 
  td,th{vertical-align:top;padding:3px 0;text-align:left;font-weight:bold;border:none;} 
  th{width:30%;text-align:right;padding-right:2%;font-weight:normal;} 
  thead th{background-color:#ebebeb;width:25%; 
  }#details-right th{width:20%;} 
  table tr.alt td,table tr.alt th{background-color:#ebebeb;} 
  .highlight-code{color:#CC0000;font-weight:bold;font-style:italic;} 
  .clear{clear:both;} 
  .preferred{padding:0 5px 2px 5px;font-weight:normal;background:#006633;color:#FFF;font-size:.8em;} 
  --&gt; 
  &lt;/style&gt; 
  
  &lt;/head&gt; 
  &lt;body&gt; 
  &lt;div id="header"&gt;&lt;h1&gt;Server Error in Application "DEFAULT WEB SITE/MYAPP"&lt;/h1&gt;&lt;/div&gt; 
  &lt;div id="server_version"&gt;&lt;p&gt;Internet Information Services 7.5&lt;/p&gt;&lt;/div&gt; 
  &lt;div id="content"&gt; 
  &lt;div class="content-container"&gt; 
   &lt;fieldset&gt;&lt;legend&gt;Error Summary&lt;/legend&gt; 
    &lt;h2&gt;HTTP Error 400.0 - Bad Request&lt;/h2&gt; 
    &lt;h3&gt;Bad Request&lt;/h3&gt; 
   &lt;/fieldset&gt; 
  &lt;/div&gt; 
  &lt;div class="content-container"&gt; 
   &lt;fieldset&gt;&lt;legend&gt;Detailed Error Information&lt;/legend&gt; 
    &lt;div id="details-left"&gt; 
     &lt;table border="0" cellpadding="0" cellspacing="0"&gt; 
      &lt;tr class="alt"&gt;&lt;th&gt;Module&lt;/th&gt;&lt;td&gt;ManagedPipelineHandler&lt;/td&gt;&lt;/tr&gt; 
      &lt;tr&gt;&lt;th&gt;Notification&lt;/th&gt;&lt;td&gt;ExecuteRequestHandler&lt;/td&gt;&lt;/tr&gt; 
      &lt;tr class="alt"&gt;&lt;th&gt;Handler&lt;/th&gt;&lt;td&gt;System.Web.Http.WebHost.HttpControllerHandler&lt;/td&gt;&lt;/tr&gt; 
      &lt;tr&gt;&lt;th&gt;Error Code&lt;/th&gt;&lt;td&gt;0x00000000&lt;/td&gt;&lt;/tr&gt; 
  
     &lt;/table&gt; 
    &lt;/div&gt; 
    &lt;div id="details-right"&gt; 
     &lt;table border="0" cellpadding="0" cellspacing="0"&gt; 
      &lt;tr class="alt"&gt;&lt;th&gt;Requested URL&lt;/th&gt;&lt;td&gt;http://localhost:80/myapp/service/link&lt;/td&gt;&lt;/tr&gt; 
      &lt;tr&gt;&lt;th&gt;Physical Path&lt;/th&gt;&lt;td&gt;C:\workspace\myapp\service\link&lt;/td&gt;&lt;/tr&gt; 
      &lt;tr class="alt"&gt;&lt;th&gt;Logon Method&lt;/th&gt;&lt;td&gt;Anonymous&lt;/td&gt;&lt;/tr&gt; 
      &lt;tr&gt;&lt;th&gt;Logon User&lt;/th&gt;&lt;td&gt;Anonymous&lt;/td&gt;&lt;/tr&gt; 
  
     &lt;/table&gt; 
     &lt;div class="clear"&gt;&lt;/div&gt; 
    &lt;/div&gt; 
   &lt;/fieldset&gt; 
  &lt;/div&gt; 
  &lt;div class="content-container"&gt; 
   &lt;fieldset&gt;&lt;legend&gt;Most likely causes:&lt;/legend&gt; 
    &lt;ul&gt;  &lt;li&gt;&lt;/li&gt; &lt;/ul&gt; 
   &lt;/fieldset&gt; 
  &lt;/div&gt; 
  &lt;div class="content-container"&gt; 
   &lt;fieldset&gt;&lt;legend&gt;Things you can try:&lt;/legend&gt; 
    &lt;ul&gt;  &lt;li&gt;Create a tracing rule to track failed requests for this HTTP status code. For more information about creating a tracing rule for failed requests, click &lt;a href="http://go.microsoft.com/fwlink/?LinkID=66439"&gt;here&lt;/a&gt;. &lt;/li&gt; &lt;/ul&gt; 
   &lt;/fieldset&gt; 
  &lt;/div&gt; 
  
  
  &lt;div class="content-container"&gt; 
   &lt;fieldset&gt;&lt;legend&gt;Links and More Information&lt;/legend&gt; 
    The request could not be understood by the server due to malformed syntax. 
    &lt;p&gt;&lt;a href="http://go.microsoft.com/fwlink/?LinkID=62293&amp;amp;IIS70Error=400,0,0x00000000,7601"&gt;View more information &amp;raquo;&lt;/a&gt;&lt;/p&gt; 
    &lt;p&gt;Microsoft Knowledge Base Articles:&lt;/p&gt; 
   &lt;ul&gt;&lt;li&gt;&lt;/li&gt;&lt;/ul&gt; 
  
   &lt;/fieldset&gt; 
  &lt;/div&gt; 
  &lt;/div&gt; 
  &lt;/body&gt; 
  &lt;/html&gt; 
  </code></pre>
  
  <p>I have tried to set <code>TrySkipIisCustomErrors = True</code> with great hope, but no luck. Any ideas? Appreciated. Thanks.</p>