jsonp with asmx error 500

问题

when i try this it works perfact

 function test() {
    debugger;
    $.ajax({ url: "http://testweb.com/myAPI.asmx/GetPersonTest",
    type: "GET",
    contentType: "application/json; charset=utf-8",
    data: { userid: 1 },
    dataType: "jsonp",
    success: function(json) {
        alert(json.UserID + ' ' + json.FirstName + ' ' + json.LastName);
    },
    error: function() {
        alert("Hit error fn!");
    }
    });
}

in the same asmx, i have another method called as below

    function Post_test(){

var newURL = window.location.protocol + '//' + window.location.host + '/' + window.location.pathname;
var user = document.getElementById('Username').value;
var email = document.getElementById('email').value;
debugger;
$.ajax({ url: "http://testweb.com/myAPI.asmx/GetPerson",
    type: "GET",
    contentType: "application/json; charset=utf-8",
    data: JSON.stringify({ username: user, emailID: email}),
    dataType: "jsonp",
    success: function(json) {
        alert(json.UserID + ' ' + json.FirstName + ' ' + json.LastName);
    },
    error: function(json) {
        alert("Hit error fn!");
    }
});


}

This method do a insert into database and return the same as GetPersonTest. But when i call this through javascript and jsonp it gives 500 server error

When i check in debugger , it gives the below error

jQuery17106155389654450119_1401518867750({"Message":"Invalid web service call, missing value for parameter: \u0027username\u0027.","StackTrace":"   at System.Web.Script.Services.WebServiceMethodData.CallMethod(Object target, IDictionary`2 parameters)\r\n   at System.Web.Script.Services.RestHandler.InvokeMethod(HttpContext context, WebServiceMethodData methodData, IDictionary`2 rawParams)\r\n   at System.Web.Script.Services.RestHandler.ExecuteWebServiceCall(HttpContext context, WebServiceMethodData methodData)","ExceptionType":"System.InvalidOperationException"});

Can anyone please help me on below. thanks

the head of method is

         <WebMethod(True)> _
    <ScriptMethod(UseHttpGet:=True, ResponseFormat:=WebMessageFormat.Json)> _
        Public Function GetPerson(ByVal username As String, ByVal emailID As String) As String

End Function

And when i check the header in developer tool it is below

callback:jQuery17106155389654450119_1401518867750
{"username":"testuser","emailID":"test@test.com"}:
_:1401518889467
Response Headersview source

回答1:

Please check the parameter username is being used in the mentioned contract method. Because, your error is showing like the missing of username parameter.

Ensure this and post your reply soon.

回答2:

Can you try with the following changes :

1. Remove 'JSON.stringify' from data parameter, so it should look like

   data : {"username": user, "emailID": email}

2. The response format is mentioned as "WebMessageFormat.Json", so change the dataType to "json", in place of "jsonp".

3. As the is being sent as querystring and not JSON, you can safely omit "contentType" (or can remove just 'application/json').

Hope this helps.

来源：https://stackoverflow.com/questions/23967360/jsonp-with-asmx-error-500