ASP.NET web API HTTP Delete 405 Method Not Allowed

I had the same problem. Adding the below code to your web.config should fix the problem under the system.webserver section:

<system.webServer>
    <validation validateIntegratedModeConfiguration="false"/>
    <modules runAllManagedModulesForAllRequests="true">
        <remove name="WebDAVModule"/>

I had the same problem, because my controller was like this:

[HttpDelete]
public HttpResponseMessage Delete(string Id)
{
     ....
}

And on the client I used the send the ID as request body:

var url = '/api/upload';
var data = JSON.stringify({ 'Id': id }); // <-- In the body
$.ajax({
    url: url,
    type: 'DELETE',
    data: data, // <-- in the body
    contentType: 'application/json'
})

When I changed the client to use it as URL parameter instead it worked:

var url = '/api/upload/' + id; // <- In the URL
$.ajax({
    url: url,
    type: 'DELETE',
    contentType: 'application/json'
});

The JavaScript code for the DELETE verb must be like this:

$.ajax({
    **url: "/api/SomeController/" + id,**
    type: "DELETE",
    dataType: "json",
    success: function(data, statusText) {
        alert(data);
    },
    error: function(request, textStatus, error) {
        alert(error);
        debugger;
    }
});

Do NOT use something like this,

...
data: {id:id}
...

as when you are using the POST method.