public class MainViewModel
{
    public string PropertyA {get;set;}
    public PartialViewModel PropertyB {get;set;}
}

public class PartialViewModel
{
    public string PropertyViewModel {get;set;}
}

@model Namespace.Models.MainViewModel
@using (Html.BeginForm("CreateMethod", "ViewController", FormMethod.Post, new { role = "form" }))
    {
        <div>
             @Html.TextBoxFor(m => m.PropertyA)
        </div>
        <div>
             @{Html.RenderPartial("_PartialView", Model.PropertyB);
        </div>
         <div>
             <input type="submit">
        </div>
    }

@model PartialViewModel
<div>
     @Html.TextBoxFor(m => m.PropertyViewModel)
</div>