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SepFrom last couple of days I was trying to call a ajax enabled wcf service method with the help of jquery. But each and every time I am getting the error code 12031 returned by the service. I did googling for this error but I was unable to find the solution. After spending much time on R&D, I found the reason why I wa geeting this error.
In this article, I am going to share my experience with you so that you will be able to resolve this error in ajax enabled wcf service. I have the below service and code for calling wcf.
WCF Service
namespace WCFBAL { [DataContract] public class Employee { [DataMember] public int EmpID; [DataMember] public string Name; [DataMember] public int Salary; [DataMember] public DateTime JoiningDate; } [ServiceContract(Namespace = "")] [AspNetCompatibilityRequirements(RequirementsMode = AspNetCompatibilityRequirementsMode.Allowed)] public class WCFBALService { [WebInvoke(Method = "POST")] public Employee GetEmpInfo(int mEmpID) { try { //suppose you have a list of employee like as in the database Listlst = new List () { new Employee { EmpID = 1, Name = "Deepak", Salary = 12000, JoiningDate = Convert.ToDateTime("11/05/2011") }, new Employee { EmpID = 2, Name = "Mohan", Salary = 18000}, new Employee { EmpID = 3, Name = "Mohan", JoiningDate = Convert.ToDateTime("06/10/2011") } }; var q = lst.Where(m => m.EmpID == mEmpID).FirstOrDefault(); Employee mobjEmp = new Employee(); if (q != null) { mobjEmp.EmpID = q.EmpID; mobjEmp.Name = q.Name; mobjEmp.Salary = q.Salary; // comment this line to expect same error //The no error will be raised since "Salary" field is of int type and default value of int variable is "0", so zero value will be assigned to it. mobjEmp.JoiningDate = q.JoiningDate; // comment this line and provide mEmpID=1 to raise error //The error will be raised since "JoiningDate" field is not being serialized because this of DateTime and this has no default value and not assign any value to it. } return mobjEmp; } catch (Exception mex) { return null; } } } }
WCF Service Method Calling Code
<script src="Scripts/jquery-1.4.1.min.js" type="text/javascript"></script> <script type="text/javascript"> $('#btn').live('click', function () { // debugger; var value = $('#txtEmpID').val(); if (value != '') { var strJSONFilterCriteria = '{"mEmpID":"' + value + '"}'; $.ajax({ type: "POST", contentType: "application/json; charset=utf-8", url: '<%=ViewState["WCFBalUrl"]%>' + '/GetEmpInfo', data: strJSONFilterCriteria, dataType: "json", error: function (msg) { // debugger; alert('Service call failed: ' + msg.status + ' Type :' + msg.statusText); }, success: function (msg) { //debugger; var str = "Emp ID:" + msg.d.EmpID + "\n"; str += "Emp Name:" + msg.d.Name + "\n"; str += "Emp Salary:" + msg.d.Salary + "\n"; //str += "JoiningDate:" + new Date(parseInt(msg.d.JoiningDate.substr(6))) + "\n"; alert(str); } }); } return false; }); </script> <h2> WCF Error Code 12031 </h2> <p> To learn more about Dot Net Tricks visit <a href="http://www.dotnet-tricks.com" title="Dot Net Tricks "> www.dotnet-tricks.com</a>. </p> <p> Enter Employee ID (1-3) </p> <p> <asp:TextBox ID="txtEmpID" runat="server" ClientIDMode="Static"></asp:TextBox> <asp:Button ID="btn" runat="server" Text="Get Info" ClientIDMode="Static" /> </p>

Summary
I hope you will enjoy this trick while programming with Ajax enabled WCF. I would like to have feedback from my blog readers. Your valuable feedback, question, or comments about this article are always welcome.
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