编辑实体框架的对象，并在ASP.NET MVC 2.0保存到数据库

问题描述

所以我知道EF实体跟踪自己的变化，他们坚持到何时调用SaveChanges数据库，但对于此方案...

So I know that EF entities track their own changes and persist them to the database when savechanges is called, but what about this scenario...

我有一个设计编辑博客帖子的页面。它有两个动作方法。

I have a page that is designed to edit a blog post. It has two action methods.

    [HttpGet]
    public ViewResult EditBlogPost(int Id)
    {
        //This action method gets the blog post by the id and returns the edit blog post page.
        BlogPost blogPost = db.BlogPosts.Where(x => x.Id == Id).FirstOrDefault();
        if (blogPost == null)
        {
            ViewData["message"] = "Blog post not found.";
            return View("Result");
        }
        return View("ManageBlogPost", blogPost);
    }

    [HttpPost]
    public ViewResult EditBlogPost(BlogPost blogPost)
    {
        //This one is where I'm having issues. When model binding populates blogPost, is it auto-tracking still? For some reason SaveChanges() doesn't seem to persist the updates.
        if (!ModelState.IsValid)
            return View("ManageBlogPost");
        db.AttachTo("BlogPosts", blogPost); //I tried this method, it seemed to be what I wanted, but it didn't help.
        db.SaveChanges();
        ViewData["message"] = "Blog post edited successfully.";
        return View("Result");
    }

下面是认为，这些回报率：

Here is the view that these return:

<%@ Page Title="" Language="C#" MasterPageFile="~/Views/Shared/Master.Master" Inherits="System.Web.Mvc.ViewPage<BlogProject.Models.BlogPost>" %>

<asp:Content ID="Content1" ContentPlaceHolderID="MainContent" runat="server">

    <% if (Model != null)
       { %>
            <h2>Edit Blog Post</h2>
    <% }
       else
       { %>
            <h2>Add Blog Post</h2>
    <% } %>
    <% using (Html.BeginForm())
       { %>
            <% if (Model != null)
               { %>
                    <%: Html.HiddenFor(x => x.Id)%> <!-- Is this the way to keep un-editable data hidden from the edit form and have them repopulate on the next model bind? What if someone went to modify their POST using something like Fiddler? Couldn't they theoretically edit these fields before the POST? -->
                    <%: Html.HiddenFor(x => x.Date) %>
                    <%: Html.HiddenFor(x => x.Author) %>
                    <%: Html.HiddenFor(x => x.FriendlyUrl) %>
            <% } %>
            Title:<br />
            <%: Html.TextBoxFor(x => x.Title, new { Style = "Width: 90%;" })%>
            <br />
            <br />
            Summary:<br />
            <%: Html.TextAreaFor(x => x.Summary, new { Style = "Width: 90%; Height: 50px;" }) %>
            <br />
            <br />
            Body:<br />
            <%: Html.TextAreaFor(x => x.Body, new { Style = "Height: 250px; Width: 90%;" })%>
            <br />
            <br />
            <input type="submit" value="Submit" />
    <% } %>

</asp:Content>

我有点困惑在这里。添加的博客文章似乎做工精细，但编辑它们是另一回事。

I'm a little confused here. Adding blog posts seems to work fine, but editing them is another story.

推荐答案

解决的办法是不要把在你编辑的操作方法的博客文章对象。相反，做一些看起来像这样：

The solution is not to take in the blog post object in your edit action method. Instead, do something that looks like this:

[HttpPost]
public ViewResult EditBlogPost(int postID)
{
    var post = db.BlogPosts.Single(p => p.PostID = postID);
    TryUpdateModel(post);

    if (!ModelState.IsValid)
        return View("ManageBlogPost");

    db.SaveChanges();

    ViewData["message"] = "Blog post edited successfully.";
    return View("Result");
}

此方式的对象附加到上下文和EF可正确地跟踪变化。在的UpdateModel 方法是一个节省时间，可以自动的形式收集到模型中的字段匹配字段和更新它们。

This way the object is attached to the context and the EF can track changes properly. The UpdateModel method is a time saver that automatically matches fields in the form collection to the fields in the model and updates them for you.

下面是的UpdateModel 的文档：

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