Why do I get error while uploading File ?

Question

This is my View :

@model SimpleUpload.Models.MemberModel

@{

ViewBag.Title = "ContactForm";

}

<h2>ContactForm</h2>

@using (Html.BeginForm("ContactForm", "Home", FormMethod.Post, new { enctype = "multipart/form-data" }))

{

@Html.AntiForgeryToken()

<div class="form-horizontal">

<h4>MemberModel</h4>

<hr />

<div class="form-group">

@Html.LabelFor(model => model.ImageFile, htmlAttributes: new { @class = "control-label col-md-2" })

<div class="col-md-10">

@Html.TextBoxFor(m => m.ImageFile, new { type = "file" })

</div>

</div>

<div class="form-group">

<div class="col-md-offset-2 col-md-10">

<input type="submit" value="Create" class="btn btn-default" />

</div>

</div>

</div>

}

I want to upload the file posted in the form group div.

This my Controller method:

[HttpGet]

public ActionResult ContactForm()

{

return View();

}

[HttpPost]

public ActionResult ContactForm(MemberModel membervalues)

{

//Use Namespace called : System.IO

string FileName = Path.GetFileNameWithoutExtension(membervalues.ImageFile.FileName);

//To Get File Extension

string FileExtension = Path.GetExtension(membervalues.ImageFile.FileName);

//Add Current Date To Attached File Name

FileName = DateTime.Now.ToString("yyyyMMdd") + "-" + FileName.Trim() + FileExtension;

//Get Upload path from Web.Config file AppSettings.

string UploadPath = ConfigurationManager.AppSettings["UserImagePath"].ToString();

//Its Create complete path to store in server.

membervalues.ImagePath = UploadPath + FileName;

//To copy and save file into server.

membervalues.ImageFile.SaveAs(membervalues.ImagePath);

return View();

}

Now, whenever I click on the submit button I find this error 'Object reference not set to an instance of an object.' on the Filename. I cannot figure out where the problem is!

Model class :

public class MemberModel

{

[DisplayName("Upload File")]

public string ImagePath { get; set; }

public HttpPostedFile ImageFile { get; set; }

}

How can I Solve this?