实体框架不会将我的数据保存到sql server

您的问题是试图通过与更新的上下文不同的上下文进行更新。以下代码是问题所在：

var vm = new ProductEditViewModel(ProductId);
UpdateModel(vm.Product, "Product");
var northwind = new NorthwindEntities();
northwind.SaveChanges();

将在vm的上下文中更新模型。线路：

var northwind = new NorthwindEntities()

创建一个尚未编辑的新上下文。您可以向ProductEditViewModel添加一个保存/更新方法（结构不好），也可以创建上下文，获取vm的实例，更新它，然后保存它。

问题是我试图通过与我更新的上下文不同的上下文进行更新。感谢BBlake先生发现问题。正确的代码如下：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
namespace MvcApplication1.Models
{
    public class Repository
    {
        public NorthwindEntities northwind;
        public Repository()
        {
            northwind = new NorthwindEntities();
        }
        public Product GetProductById(Int32 ProductId)
        {
            return (from pro in northwind.Products
                    where pro.ProductID == ProductId
                    select pro).FirstOrDefault();
        }
        public void Save()
        {
            this.northwind.SaveChanges();
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;
namespace MvcApplication1.Models
{
    public class ProductEditViewModel
    {
        public Repository repository = new Repository();
        public Product Product;
        public ProductEditViewModel()
        {
            ;
        }
        // For DropDownListFor need IEnumerable<SelectListItem>
        public IEnumerable<SelectListItem> SupplierItems
        {
            get
            {
                var q = from sup in repository.northwind.Suppliers.AsEnumerable()
                        select new SelectListItem
                            {
                                Text = sup.CompanyName,
                                Value = sup.SupplierID.ToString(),
                                Selected = sup.SupplierID == Product.SupplierID
                            };
                return q;
            }
        }
        // For RadioButtonFor need below
        public IEnumerable<Category> CategorieItems
        {
            get
            {
                var q = from cat in repository.northwind.Categories.AsEnumerable() select cat;
                return q;
            }
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;
using System.Web.Script.Serialization;
using MvcApplication1.Models;
using System.Data.Objects.SqlClient;
using System.Data;
namespace MvcApplication1.Controllers
{
    public class HomeController : Controller
    {
        ProductEditViewModel vm = new ProductEditViewModel();
        // sample for populate sql server database table via entity framework
        // 1. Install EntityFramework 5.0, if previous sample for using populate oracle database table via entity framework has been installed, this can be skiped : execute command at Package Manager Console "Install-Package EntityFramework -Version 5.0.0" ( Oracle data access provider ODAC 12.1.0.1.2 current is not support (work with) EntityFramework version 6 ). If you want uninstall EntityFramework 5, using command "unInstall-Package EntityFramework -Version 5.0.0"
        // 2. Models => Add => New item => Data => Ado.Net Entity Data Model ( using EntityFramework 5.0 )
        public ActionResult ProductList()
        {
            var northwind = new NorthwindEntities(); // 3. this is connectionStrings name="NorthwindEntities"
            var q = from pro in northwind.Products
                    select new ProductListViewModel
                    {
                        ProductId = pro.ProductID,
                        ProductName = pro.ProductName,
                        Supplier = pro.Supplier.CompanyName,
                        Categorie = pro.Category.CategoryName,
                        Discontinued = pro.Discontinued,
                        UnitPrice = pro.UnitPrice
                    };
            return View(q.ToList());
        }
        [HttpGet]
        public ActionResult ProductEdit(Int32 ProductId)
        {
            vm.Product = vm.repository.GetProductById(ProductId);
            return View(vm);
        }
        [HttpPost]
        public ActionResult ProductEdit(Int32 ProductId, FormCollection fc)
         {
            vm.Product = vm.repository.GetProductById(ProductId);
            UpdateModel(vm.Product, "Product");
            vm.repository.Save();
            return RedirectToAction("ProductList");
        }
    }
}

@model MvcApplication1.Models.ProductEditViewModel
@{
    Layout = null;
}
<script type="text/javascript">
</script>
<!DOCTYPE html>
<html>
<head>
    <meta name="viewport" content="width=device-width" />
    <title>ProductEdit</title>
</head>
<body>
    <script src="~/Scripts/jquery-1.10.2.min.js"></script>
    <script src="~/Scripts/jquery.validate.min.js"></script>
    <script src="~/Scripts/jquery.validate.unobtrusive.min.js"></script>

    @using (Html.BeginForm())
    {
        @Html.AntiForgeryToken()
        <div class="form-horizontal">
            <h4>Product</h4>
            <hr />
            @Html.ValidationSummary(true, "", new { @class = "text-danger" })
            @Html.HiddenFor(model => model.Product.ProductID)
            <div class="form-group">
                @Html.LabelFor(model => model.Product.ProductName, htmlAttributes: new { @class = "control-label col-md-2" })
                <div class="col-md-10">
                    @Html.EditorFor(model => model.Product.ProductName, new { htmlAttributes = new { @class = "form-control" } })
                    @Html.ValidationMessageFor(model => model.Product.ProductName, "", new { @class = "text-danger" })
                </div>
            </div>
            <div class="form-group">
                @Html.LabelFor(model => model.Product.SupplierID, "SupplierID", htmlAttributes: new { @class = "control-label col-md-2" })
                <div class="col-md-10">
                    @*DropDownList is for deiplay purpose*@
                    @*@Html.DropDownList("SupplierID", Model.SupplierItems, htmlAttributes: new { @class = "form-control" })*@
                    @*DropDownListFor is for Edit purpose*@
                    @Html.DropDownListFor(model => model.Product.SupplierID, Model.SupplierItems, htmlAttributes: new { @class = "form-control" })
                </div>
            </div>
            <div class="form-group">
                @Html.LabelFor(model => model.Product.CategoryID, "CategoryID", htmlAttributes: new { @class = "control-label col-md-2" })
                <div class="col-md-10">
                    @*RadioButton is for Display purpose*@
                    @*@foreach (var Categorie in Model.CategorieItems)
                        {
                            @Html.RadioButton("CategoryID", Categorie.CategoryID, Model.CategorySelectedId == Categorie.CategoryID) @Categorie.CategoryName; @:&nbsp;&nbsp;&nbsp;
                        }*@
                    @*RadioButtonFor is for Edit purpose*@
                    @foreach (var Categorie in Model.CategorieItems)
                    {
                        @Html.RadioButtonFor(model => model.Product.CategoryID, Categorie.CategoryID) @Categorie.CategoryName; @:&nbsp;&nbsp;&nbsp;
                    }
                </div>
            </div>
            <div class="form-group">
                @Html.LabelFor(model => model.Product.UnitPrice, htmlAttributes: new { @class = "control-label col-md-2" })
                <div class="col-md-10">
                    @Html.EditorFor(model => model.Product.UnitPrice, new { htmlAttributes = new { @class = "form-control" } })
                    @Html.ValidationMessageFor(model => model.Product.UnitPrice, "", new { @class = "text-danger" })
                </div>
            </div>
            <div class="form-group">
                @Html.LabelFor(model => model.Product.Discontinued, htmlAttributes: new { @class = "control-label col-md-2" })
                <div class="col-md-10">
                    <div class="checkbox">
                        @Html.EditorFor(model => model.Product.Discontinued)
                        @Html.ValidationMessageFor(model => model.Product.Discontinued, "", new { @class = "text-danger" })
                    </div>
                </div>
            </div>
            <div class="form-group">
                <div class="col-md-offset-2 col-md-10">
                    <input type="submit" value="Save" class="btn btn-default" />
                </div>
            </div>
        </div>
    }
    <div>
        @Html.ActionLink("Back to List", "Index")
    </div>
</body>
</html>