MVC : System.NullReferenceException model when submit form - asp.net-mvc-4

Question

I've been trying to pass a model to a partial view with a form. Some of the model fields are already assigned in the GET request. When the form loads I can see the model fields values but after
submiting the form I get this error in this line: #Html.Hidden("From",Model.From):
Object reference not set to an instance of an object
Why these two fields are assigned with null on submit?
My controllers:
[HttpGet]
public ActionResult SendPrivateMessage(string from, List<string> to)
{
// two of the fields are already assigned
return PartialView("SendMessage", new MessageModel(from,to));
}
[HttpPost]
public ActionResult SendPrivateMessage(MessageModel m)
{
string fullname = "";
LoginModel loginData = (LoginModel)(Session["user"]);
if (Session["user"] != null)
{
fullname = loginData.LoginDS.Tables[0].Rows[0][loginData.LoginDS.Tables[0].Columns["fullname"].Ordinal].ToString();
}
m.fullname = fullname;
m.Send();
return PartialView("SendMessage");
}
The partial view:
#model HaifanetMobile.Models.MessageModel
<div id="contact_form">
<a id="back_contact" href="#" style="float:left">
<img style="height:20px; width:30px;" src="~/Images/back_btn.gif" alt="back" />.
</a>
<div id="contactus_title">
<div id="close_contactus" style="float:right"><img style="height:20px; width:20px;" src="~/Images/close_btn.gif" /></div>
</div>
#using (Html.BeginForm())
{
#Html.ValidationSummary(true)
<br />
<fieldset>
#Html.Hidden("From", Model.From) //this is where I get the error
#Html.Hidden("To", Model.To)//this is where I get the error
<div>
#Html.TextBoxFor(m => m.Subject, new { #class = "", placeholder = "subject:", id = "msg_subject", onfocus = "this.placeholder = ''", onblur = "this.placeholder = 'subject:'" })
#Html.ValidationMessageFor(m => m.Subject, "required")
</div>
<div>
#Html.TextAreaFor(m => m.Content, new { #class = "", id = "msg_textarea" })
#Html.ValidationMessageFor(m => m.Content, "required")
</div>
</fieldset>
<p>
<input type="submit" value="send" />
</p>
}
</div>
The Model:
public class MessageModel
{
public string From { get; set; }
public List<string> To { get; set; }
public string Subject {get; set;}
public string Content { get; set; }
public string fullname { get; set; }
public MessageModel(string from, List<string> to)
{
// TODO: Complete member initialization
this.From = from;
this.To = to; ;
}
public MessageModel() {
}
public void Send()
{
ServiceReference2.WebService1Soap ws = new ServiceReference2.WebService1SoapClient();
if (!ws.SendMessage(this.From, this.Content, this.Subject, this.To.ToArray() ,this.fullname))
throw new Exception();
}
}
Thanks in advance

Answer 1

You're forgetting to pass the model to your view.
When you return this view, instead of this:
return PartialView("SendMessage");
you must do this:
return PartialView("SendMessage", m);
Where m is your model. That's why the model is null inside your view.