The parameterized query '(@id nvarchar(4000),@name nvarchar(4000),@project nvarchar(4000)' expects the parameter '@id', which was not...

The parameterized query '(@id nvarchar(4000),@name nvarchar(4000),@project
nvarchar(4000)' expects the parameter '@id', which was not...

while storing data into database through wcf I am getting error. I am
taking input from android client through textboxes. ERROR: The
parameterized query '(@id nvarchar(4000),@name nvarchar(4000),@project
nvarchar(4000)' expects the parameter '@id', which was not supplied.
The c# code for data insertion is
[DataContract]
public class studentinfo
{
[DataMember(Name = "ID")]
public string ID { get; set; }
[DataMember(Name = "Name")]
public string Name { get; set; }
[DataMember(Name = "Project")]
public string Project { get; set; }
[DataMember(Name = "Result")]
public string Result { get; set; }
}
[OperationContract]
[WebInvoke(Method = "POST", RequestFormat = WebMessageFormat.Json,
ResponseFormat = WebMessageFormat.Json, UriTemplate = "SaveData")]
void SaveData(studentinfo studentinfo);
public void SaveData(studentinfo studentinfo)
{
SqlConnection con;
con = new
SqlConnection(ConfigurationManager.ConnectionStrings["Myproject.Properties.Settings.MyConnection"].ConnectionString);
if (con.State == ConnectionState.Closed)
{
con.Open();
}
SqlCommand cmd = new SqlCommand("INSERT INTO Result
(ID,Name,Project,Result) values(@ID,@Name,@Project,@Result)", con);
cmd.Parameters.AddWithValue("@ID", studentinfo.ID);
cmd.Parameters.AddWithValue("@Name", studentinfo.Name);
cmd.Parameters.AddWithValue("@Project", studentinfo.Project);
cmd.Parameters.AddWithValue("@Result", studentinfo.Result);
int Valid = cmd.ExecuteNonQuery();
con.Close();
}
I did try some methods provided in other answers but unable to solve this
problem.