打开图表页面时出现“No http handler was found for request type 'GET'”错误求助

Hey there, let's work through that "No http handler was found for request type 'GET'" error you're seeing when loading the page with charts. I've dealt with similar issues before, so here are some targeted steps to troubleshoot:

1. Verify HTTP Handler Registration for Chart Requests #

If your charts rely on ASP.NET's built-in Chart control or a custom handler, the first thing to check is whether the handler is properly registered in your web.config and allows GET requests.

For IIS 6.x, look for the <httpHandlers> section; for IIS 7+ integrated mode, check <system.webServer><handlers>. Here's how the ASP.NET Chart handler should be configured (make sure verb includes GET):

<!-- IIS 6.x configuration -->
<system.web>
  <httpHandlers>
    <add path="ChartImg.axd" verb="GET,HEAD,POST" 
         type="System.Web.UI.DataVisualization.Charting.ChartHttpHandler, System.Web.DataVisualization, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" 
         validate="false" />
  </httpHandlers>
</system.web>

<!-- IIS 7+ Integrated Mode configuration -->
<system.webServer>
  <handlers>
    <add name="ChartImageHandler" preCondition="integratedMode" 
         verb="GET,HEAD,POST" path="ChartImg.axd" 
         type="System.Web.UI.DataVisualization.Charting.ChartHttpHandler, System.Web.DataVisualization, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" />
  </handlers>
</system.webServer>

If your existing handler entry doesn't include GET in the verb attribute, adding it should fix the immediate issue.

2. Enable GET Requests for Your ASMX Web Services #

Looking at your appSettings, you're referencing ASMX web services (MyWebService.webserviceGeneral and ElectricWSL.WebService). By default, ASMX services block GET requests for security reasons. If your chart is trying to fetch data via GET, you'll need to enable it in web.config:

<system.web>
  <webServices>
    <protocols>
      <add name="HttpGet"/>
      <add name="HttpPost"/>
    </protocols>
  </webServices>
</system.web>

This allows your services to accept both GET and POST requests, which might be what your chart component is using to load data.

3. Check IIS Handler Mappings (Server-Side) #

If you're hosting on IIS, head over to IIS Manager:

• Navigate to your site → Handler Mappings
• Look for the handler related to your chart requests (e.g., ChartImageHandler or your custom service handler)
• Double-check that it's enabled and that the Allowed Verbs include GET
• If the handler is missing, you might need to re-register it via IIS or update your web.config

4. Confirm Required Assemblies Are Present #

If you're using the ASP.NET Chart control, make sure the System.Web.DataVisualization.dll file is in your application's bin folder. Even if the handler is registered correctly, missing this assembly will cause handler-related errors.

If none of these steps resolve the issue, could you share the full web.config (redact any sensitive URLs/keys) and a bit more context about the chart component you're using? Knowing whether it's a built-in ASP.NET Chart, a third-party library, or a custom solution will help narrow things down further.

内容的提问来源于stack exchange，提问作者David Izhaki