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I have a problem with passing a JSON object using Ajax and ASP.NET WebMethods

function setStudentInfo() {
    var jsonObjects = [
        { id: 1, name: "mike" },
        { id: 2, name: "kile" },
        { id: 3, name: "brian" },
        { id: 1, name: "tom" }
    ];

    $.ajax({
        type: "POST",
        url: "ConfigureManager.aspx/SetStudentInfo",
        contentType: "application/json; charset=utf-8",
        dataType: "json",
        async: false,
        data: { students: JSON.stringify(jsonObjects) },
        success: function (result) {
            alert('success');
        },
        error: function (result) {
            alert(result.responseText);
        }

    });
}

ASP.NET code

[WebMethod]
public static void SetStudentInfo(object students)
{
     //Here I want to iterate the 4 objects and to print their name and id
}

I am getting the following error:

"{"Message":"Invalid JSON primitive: students.","StackTrace":" at System.Web.Script.Serialization.JavaScriptObjectDeserializer.DeserializePrimitiveObject() at System.Web.Script.Serialization.JavaScriptObjectDeserializer.DeserializeInternal(Int32 depth) at System.Web.Script.Serialization.JavaScriptObjectDeserializer.BasicDeserialize(String input, Int32 depthLimit, JavaScriptSerializer serializer) at System.Web.Script.Serialization.JavaScriptSerializer.Deserialize(JavaScriptSerializer serializer, String input, Type type, Int32 depthLimit) at System.Web.Script.Serialization.JavaScriptSerializer.Deserialize[T](String input) at System.Web.Script.Services.RestHandler.GetRawParamsFromPostRequest(HttpContext context, JavaScriptSerializer serializer) at System.Web.Script.Services.RestHandler.GetRawParams(WebServiceMethodData methodData, HttpContext context) at System.Web.Script.Services.RestHandler.ExecuteWebServiceCall(HttpContext context, WebServiceMethodData methodData)","ExceptionType":"System.ArgumentException"}"

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And what problem are you experiencing (more specifically)? – Mario Nov 19 '12 at 7:11

3 Answers

up vote 0 down vote

You aren't actually sending json to the server, to send json just pass a json string for the data property.

data: JSON.stringify(jsonObjects),
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when performing your change i am getting the following" "{"Message":"Type \u0027System.Collections.Generic.IDictionary`2[[System.String, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089],[System.Object, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]]\u0027 is not supported for deserialization of an array.","StackTrace":" at System.Web.Script.Serialization.ObjectConverter.ConvertListToObject(IList list, Type type, JavaScriptSerializer serializer, Boolean throwOnError, IList& convertedList – user829174 Nov 19 '12 at 7:20
@user829174 I don't know much about asp.net but it looks like your webmethod is expecting an object and getting an array. – Musa Nov 19 '12 at 7:23
thank you for your feedback, to what should i change the signature of my method so i will be able to send that particular JSON object to the server, can you share a code? – user829174 Nov 19 '12 at 7:27
up vote 0 down vote

Pass your entire JSON as a string, like this:

data: '{variable: "value"}'

I always get an error if I try to pass it as you have.

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can you please give a code example. thanks – user829174 Nov 19 '12 at 7:21
Keys need to be quoted also. – Musa Nov 19 '12 at 7:24
I don't get errors if I leave the keys unquoted. – Yatrix Nov 19 '12 at 14:27
up vote 0 down vote

You are getting that error because a single Object is expected but your code is expecting a List of Objects. This can be a bit tricky sometimes. To make the data transfer easier, you should create a class with properties for the type of object you want to pass to the WebMethod, because it seems to be easier for ASP.NET to parse that. For example:

public class Student
{
    private string _name;
    private int _id;
    public string name {
        get { return _name; }
        set { _name = value; }
    }
    public int id {
        get { return _id; }
        set { _id = value; }
    }
}

And then your WebMethod will change to accept a List of Student Class Objects, like so:

[WebMethod]
public static void SetStudentInfo(List<Student> Students)
{
    foreach (Student s in Students)
    {
        //Do whatever here System.Console.WriteLine(s.name);
    }
}

Then all you need to do is slightly change your Ajax call like so:

function setStudentInfo() {
    var jsonObjects = [
        { id: 1, name: "mike" },
        { id: 2, name: "kile" },
        { id: 3, name: "brian" },
        { id: 1, name: "tom" }
    ];

    $.ajax({
        type: "POST",
        url: "ConfigureManager.aspx/SetStudentInfo",
        contentType: "application/json; charset=utf-8",
        dataType: "json",
        async: false,
        data: { Students: JSON.stringify(jsonObjects) },
        success: function (result) {
            alert('success');
        },
        error: function (result) {
            alert(result.responseText);
        }

    });
}
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