MVC Model not posting - post

Question

When I click the login button I never get my model posted to the server. However if I accept a FormCollection I will see the values. How can I make this automatically bind to my model instead of searching the Form Collection?
From what I have read there are a few common problems for this:
1 - your view does not specify what model you are using (#model myApp.Models.name)
2 - Your model does not use properties
3 - Any of the required fields are missing
Controller
[HttpGet]
public ActionResult Password()
{
return View(new AuthViewModel());
}
[HttpPost]
public ActionResult Password(AuthViewModel password)
{
if (password == null || string.IsNullOrEmpty(password.Password))
{
ViewBag.Error = Constants.ErrorMessages.UserPassword_PassBlank;
return View(new AuthViewModel());
}
//success
return Redirect("/");
}
Model
public class AuthViewModel
{
public string Password { get; set; }
}
View
#model MvcApplication1.Models.AuthViewModel
#{
ViewBag.Title = "Password";
}
<h2>Password</h2>
#using (Html.BeginForm())
{
<div>#Html.TextBoxFor(m => m.Password,new{placeholder="Password",type="password",autofocus=""})</div>
<div><button id="btnLogin" type="submit">Login</button></div>
<div class="error">#ViewBag.Error</div>
}

Answer 1

Not sure why Dan's answer isn't working without trying it, looks like it should.
I took a look at some of my code for a login form, similar to yours.
Here's mine :
public class SignInModel
{
[Required]
[Display(Name = "Enter your email address")]
public string Email { get; set; }
[Required]
[DataType(DataType.Password)]
[Display(Name = "Enter your password")]
public string Password { get; set; }
[Display(Name = "Remember me?")]
public bool RememberMe { get; set; }
}
The main difference I see is that mine has the [DataType(DataType.Password)] attribute on the password. Not sure if this makes that much difference though.
The other thing I noticed is different is that in my form I specify that the form method is POST. Also I've used the EditorFor() helper instead of textbox or password:
#using (Html.BeginForm("SignIn", "Account", "POST"))
{
<div class="form-field">
#Html.LabelFor(x => x.Email)
#Html.EditorFor(m => m.Email)
</div>
<div class="form-field">
#Html.LabelFor(x => x.Password)
#Html.EditorFor(m => m.Password)
</div>
<div class="form-remember">
#Html.CheckBoxFor(m => m.RememberMe)
#Html.LabelFor(x => x.RememberMe)
</div>
<button type="submit">
Sign In</button>
}

Answer 2

use the following
#using (Html.BeginForm())
{
<div>#Html.PasswordFor(model => model.Password)</div>
<div><input id="btnLogin" type="submit" value="Login"/></div>
<div class="error">#ViewBag.Error</div>
}