About Ajax cross-domain calls to ASP. NET MVC or WEBAPI services problems and solutions

Problem description

When cross domain calls the services written by ASP. NET MVC or the ASP. NET Web API, an inaccessible condition occurs.

How to Reproduce

1. Create one of the simplest ASP. NET Web API projects with a template and debug to confirm that it works

2. Create another project that contains only an HTML page, initiating an AJAX call

3. Open this page in the browser, we will find the following error (405:method not allowed)

   "Remarks" in the same case, also occurs in ASP. At some point, MVC can also be used to develop services directly, with advantages and disadvantages compared to WEBAPI. The following is an example of a service developed using MVC

Cause analysis

A cross-domain problem occurs only when JavaScript initiates an Ajax call, or when Silverlight initiates a service invocation, because the browser is given a lower permission for both requests, usually allowing only the resources in the domain to be called. Unless the target server explicitly tells it to allow cross-domain calls.

Therefore, the cross-domain problem is caused by the behavior of the browser, but the solution is on the server side. Because it is not possible to require all clients to reduce security.

Solution Solutions

For the two project types of ASP. NET MVC and ASP, I did some research to make sure the following scenario is feasible.

For ASP. NET MVC, just add the following in Web. config

<system.webServer>

<customHeaders>

<add name= "Access-control-allow-origin" value= "*"/>

<add name= "Access-control-allow-headers" value= "Content-type"/>

<add name= "Access-control-allow-methods" value= "GET, POST, PUT, DELETE, OPTIONS"/>

</customHeaders>

<remove name= "extensionlessurlhandler-integrated-4.0"/>

<remove name= "Optionsverbhandler"/>

<remove name= "Traceverbhandler"/>

<add name= "extensionlessurlhandler-integrated-4.0" path= "*." verb= "*" type= " System.Web.Handlers.TransferRequestHandler "precondition=" integratedmode,runtimeversionv4.0 "/>

</system.webServer>

In addition to the above settings, for the ASP. NET Web API, you need to add a special design that adds an options method to each Apicontroller, but does not need to return anything.

public string Options ()

{

return null; HTTP response with empty body

}

About Ajax cross-domain calls to ASP. NET MVC or WEBAPI services problems and solutions