System.Reflection.AmbiguousMatchException while parsing json

unfortunately I have zero experience in C#, but I need to create JSON source in SSIS.

I'm trying to download JSON, deserialize and save it to list:

public override void CreateNewOutputRows()
{
    JavaScriptSerializer serialize = new JavaScriptSerializer();

    var employees = new List<Employees>();

    employees = serialize.Deserialize<List<Employees>>(json);


    foreach (var record in employees)
    {
        Output0Buffer.AddRow();

        Output0Buffer.FirstName = record.FirstName;
        Output0Buffer.EmailId = record.EmailID;
        Output0Buffer.Profile = record.Profile;
        Output0Buffer.EmployeeIDInternal = record.EmployeeIDInternal;
        Output0Buffer.LastName = record.LastName;
    }
}

Employees is:

public class Employees
{
    public string FirstName { get; set; }
    public string EmailID { get; set; }
    public string Profile { get; set; }
    public string EmployeeIDInternal { get; set; }
    public string LastName { get; set; }
}

But it fails with following error:

System.Reflection.AmbiguousMatchException
  HResult=0x8000211D
  Message=Ambiguous match found.
  Source=mscorlib

UPD: @OlivierJacot-Descombes I can't show you original json, but I tried approach from JavaScriptSerializer method documentation by creating json from serializer:

var RegisteredUsers = new List<Employees>();
RegisteredUsers.Add(new Employees() { FirstName = "Name1", EmailID = "abc@gmail.com", Profile = "DB", EmployeeIDInternal = "123", LastName = "Surname1" });
RegisteredUsers.Add(new Employees() { FirstName = "Name2", EmailID = "abc1@gmail.com", Profile = "DB1", EmployeeIDInternal = "1234", LastName = "Surname2" });
RegisteredUsers.Add(new Employees() { FirstName = "Name3", EmailID = "abc234@gmail.com", Profile = "SQL", EmployeeIDInternal = "77", LastName = "Surname3" });
RegisteredUsers.Add(new Employees() { FirstName = "Name4", EmailID = "absdfsc@gmail.com", Profile = "", EmployeeIDInternal = "555", LastName = "Surname4" });

var serializer = new JavaScriptSerializer();
var serializedResult = serializer.Serialize(RegisteredUsers);


var employees = serializer.Deserialize<List<Employees>>(serializedResult);

it generates following json text (the original is unformatted on a single line of text):

[
   {
      "modifiedTime":null,
      "Addedtime":null,
      "FirstName":"Name1",
      "EmailID":"abc@gmail.com",
      "Photo":null,
      "HRSpecialist":null,
      "AddedBy":null,
      "Gender":null,
      "ApprovalStatus":null,
      "Profile":"DB",
      "CarNumberPlate":null,
      "recordId":null,
      "ModifiedBy":null,
      "Department":null,
      "EmployeeIDInternal":"123",
      "Modifiedtime":null,
      "ownerName":null,
      "createdTime":null,
      "TechnicalLevel":null,
      "Room":null,
      "Tags":null,
      "Photo_downloadUrl":null,
      "ReportingTo":null,
      "FirstProject":null,
      "Designation":null,
      "IM":null,
      "WorkLocation":null,
      "ownerID":null,
      "MaritalStatus":null,
      "DateofJoining":null,
      "IMServiceProvider":null,
      "CompetenceLead":null,
      "DateofBirth":null,
      "LastName":"Surname1",
      "EmployeeID":null,
      "MobilePhone":null,
      "Expertise":null,
      "Location":null
   },
   {
      "modifiedTime":null,
      "Addedtime":null,
      "FirstName":"Name2",
      "EmailID":"abc1@gmail.com",
      "Photo":null,
      "HRSpecialist":null,
      "AddedBy":null,
      "Gender":null,
      "ApprovalStatus":null,
      "Profile":"DB1",
      "CarNumberPlate":null,
      "recordId":null,
      "ModifiedBy":null,
      "Department":null,
      "EmployeeIDInternal":"1234",
      "Modifiedtime":null,
      "ownerName":null,
      "createdTime":null,
      "TechnicalLevel":null,
      "Room":null,
      "Tags":null,
      "Photo_downloadUrl":null,
      "ReportingTo":null,
      "FirstProject":null,
      "Designation":null,
      "IM":null,
      "WorkLocation":null,
      "ownerID":null,
      "MaritalStatus":null,
      "DateofJoining":null,
      "IMServiceProvider":null,
      "CompetenceLead":null,
      "DateofBirth":null,
      "LastName":"Surname2",
      "EmployeeID":null,
      "MobilePhone":null,
      "Expertise":null,
      "Location":null
   },
   {
      "modifiedTime":null,
      "Addedtime":null,
      "FirstName":"Name3",
      "EmailID":"abc234@gmail.com",
      "Photo":null,
      "HRSpecialist":null,
      "AddedBy":null,
      "Gender":null,
      "ApprovalStatus":null,
      "Profile":"SQL",
      "CarNumberPlate":null,
      "recordId":null,
      "ModifiedBy":null,
      "Department":null,
      "EmployeeIDInternal":"77",
      "Modifiedtime":null,
      "ownerName":null,
      "createdTime":null,
      "TechnicalLevel":null,
      "Room":null,
      "Tags":null,
      "Photo_downloadUrl":null,
      "ReportingTo":null,
      "FirstProject":null,
      "Designation":null,
      "IM":null,
      "WorkLocation":null,
      "ownerID":null,
      "MaritalStatus":null,
      "DateofJoining":null,
      "IMServiceProvider":null,
      "CompetenceLead":null,
      "DateofBirth":null,
      "LastName":"Surname3",
      "EmployeeID":null,
      "MobilePhone":null,
      "Expertise":null,
      "Location":null
   },
   {
      "modifiedTime":null,
      "Addedtime":null,
      "FirstName":"Name4",
      "EmailID":"absdfsc@gmail.com",
      "Photo":null,
      "HRSpecialist":null,
      "AddedBy":null,
      "Gender":null,
      "ApprovalStatus":null,
      "Profile":"",
      "CarNumberPlate":null,
      "recordId":null,
      "ModifiedBy":null,
      "Department":null,
      "EmployeeIDInternal":"555",
      "Modifiedtime":null,
      "ownerName":null,
      "createdTime":null,
      "TechnicalLevel":null,
      "Room":null,
      "Tags":null,
      "Photo_downloadUrl":null,
      "ReportingTo":null,
      "FirstProject":null,
      "Designation":null,
      "IM":null,
      "WorkLocation":null,
      "ownerID":null,
      "MaritalStatus":null,
      "DateofJoining":null,
      "IMServiceProvider":null,
      "CompetenceLead":null,
      "DateofBirth":null,
      "LastName":"Surname4",
      "EmployeeID":null,
      "MobilePhone":null,
      "Expertise":null,
      "Location":null
   }
]

The Employees class seems to have many more properties or fields than you are showing us.

In your JSON text I see two entries per record that are similar:

"modifiedTime":null,                                field #1
"Modifiedtime":null,                                field #16

They are only distinguished by the letter case. They are most probably the origin of the System.Reflection.AmbiguousMatchException. Either rename one of them of remove one of them.

One is possibly a property while the other one is a field. See: How to exclude property from Json Serialization