>>Hi everybody,
>>
>>When I try to save data using jquery ui dialog I am getting the following error (few lines from the stack in FireBug console HTML):
>>

>>[MissingMethodException: No parameterless constructor defined for this object.]
>>   System.RuntimeTypeHandle.CreateInstance(RuntimeType type, Boolean publicOnly, Boolean noCheck, Boolean& canBeCached, RuntimeMethodHandleInternal& ctor, Boolean& bNeedSecurityCheck) +0
>>   System.RuntimeType.CreateInstanceSlow(Boolean publicOnly, Boolean skipCheckThis, Boolean fillCache, StackCrawlMark& stackMark) +113
>>   System.RuntimeType.CreateInstanceDefaultCtor(Boolean publicOnly, Boolean skipCheckThis, Boolean fillCache, StackCrawlMark& stackMark) +232
>>   System.Activator.CreateInstance(Type type, Boolean nonPublic) +83
>>   System.Activator.CreateInstance(Type type) +6
>>   System.Web.Mvc.DefaultModelBinder.CreateModel(ControllerContext controllerContext, ModelBindingContext bindingContext, Type modelType) +183
>>   System.Web.Mvc.DefaultModelBinder.BindComplexModel(ControllerContext controllerContext, ModelBindingContext bindingContext) +564
>>   System.Web.Mvc.DefaultModelBinder.BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext) +416
>>   System.Web.Mvc.ControllerActionInvoker.GetParameterValue(ControllerContext controllerContext, ParameterDescriptor parameterDescriptor) +317
>>   System.Web.Mvc.ControllerActionInvoker.GetParameterValues(ControllerContext controllerContext, ActionDescriptor actionDescriptor) +117
>>   System.Web.Mvc.Async.<>c__DisplayClass25.<BeginInvokeAction>b__1e(AsyncCallback asyncCallback, Object asyncState) +446
>>

>>I made some searches and I think it may be related to my model?
>>
>>The ViewModel is defined this way:
>>
>>

>>using System;
>>using System.Collections.Generic;
>>using System.Linq;
>>using System.Web;
>>using System.Web.Mvc;
>>using CardNumbers.Objects;
>>using System.ComponentModel.DataAnnotations;
>>using System.ComponentModel;
>>
>>using DataAnnotationsExtensions;
>>using System.ComponentModel.DataAnnotations.Schema;
>>
>>namespace CardNumbers.Models
>>{
>>    public class ClientViewModel
>>    {
>>        public Client Client { get; set; }
>>
>>        [Key]
>>        [Editable(false)]
>>        [Column("ClientId", TypeName = "int")]
>>        public virtual int? ClientId
>>        {
>>            get
>>            {
>>                if (Client == null)
>>                    return null;
>>                else
>>                    return Client.Id;
>>            }
>>
>>            set { Client.Id = value ?? 0; }
>>        }
>>        [Required]
>>        [DisplayName("Client No")]
>>        [UIHint("Number")]
>>        [Column("client_no", TypeName = "smallint")]
>>        [Remote("doesClientNoExist", "Client", HttpMethod = "POST",
>>            AdditionalFields = "ClientId",
>>            ErrorMessage = "Client Number already exists. Please enter a different Client Number.")]
>>        public virtual Int16 ClientNumber
>>        {
>>            get
>>            {
>>                if (Client == null)
>>                    return 0;
>>                else
>>                    return Client.Number;
>>            }
>>
>>            set { Client.Number = value; }
>>        }
>>
>>        [Required]
>>        [Column("client_name", TypeName = "varchar")]
>>        [DisplayName("Client Name")]
>>        [MaxLength(30, ErrorMessage = "Client Name should not be longer than 30 characters")]
>>        [MinLength(3, ErrorMessage = "Client Name is too short")]
>>        [Remote("doesClientNameExist", "Client", HttpMethod = "POST", AdditionalFields = "ClientId",
>>            ErrorMessage = "Client Name already exists. Please enter a different Client Name.")]
>>        public virtual string ClientName
>>        {
>>            get
>>            {
>>                if (Client == null)
>>                    return "";
>>                else 
>>                    return Client.Name;            
>>            }
>>
>>            set { Client.Name = value; }
>>        }
>>
>>        public int id { get; set; }
>>       /// <summary>
>>       /// Public constructor
>>       /// </summary>
>>       /// <param name="client"></param>
>>        public ClientViewModel(Client client = null)
>>        {
>>           if (client != null)
>>              this.Client = client;
>>           else
>>              this.Client = new Client();
>>        }
>>    }
>>}

>>
>>Could the error above be related to that public constructor? But I am using default value for the parameter in the constructor, so I don't think it means I do not have constructor without parameter?
>
>The answer is the first line of the error. A constructor with an optional parameter is *not* a parameterless constructor...
>
This is what I started to think. I'll try to just add

public ClientViewModel
{
}

and see if this will resolve the problem.