500 error from a RESTful web service which doesn't even act on the http request

I have a set of ASP.Net pages running on IIS7. Being RESTful, we expect to receive some XML. This is not going to be a public service so the XML format is agreed upon. We need this service as an integration between two sites and the the service pushes data in one direction.

I tested how it works by using the Poster add-on for Firefox and everything went fine. However, the expected caller would be another website (making a server side call every few hours or upon user action) and I get the expected response.

However, when we try and call it from the other site (from where it needs to work) it throws an 500 error.

I weren't sure which part of the code was creating a problem so we commented out the whole of Page_Load() and still the same!

I tried with cURL, through some other code but only the calls from the server is throwing a 500. The I开发者_如何学JAVAIS logs confirm the right URL is being called. I even tried making calls using the same User Agent, but my web service doesn't like that server alone.

Am really scratching my head on this one - how can no code at all throw a 500? Could it be because of some HTTP headers or maybe the server is sending a SOAPAction header?

(I cannot confirm this right now because am out of office ATM)

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Alright, I was sending the XML POST directly and the server was sending it as a param - xmlObject= and validateRequest was true.

Thanks Carson63000 for the comment!

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I had the same issue, which turned out to be a simple mistake in the web method parameters. My Web Method was doSomething(int parameter) but I was calling it with doSomething?parameter=1.0 i.e a double.

Seems IIS/ASP throws this HTTP 500 exception when it cant translate the parameter into the type that the web method is expecting.

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In my opinion, the two most common sources of 500 response codes, in ASPNET, are:

• Web.config is corrupted or broken
• global.asax is throwing an exception

See also, this blog entry on troubleshooting 500 errors.