Question

尝试使用MVC从我的数据库中删除记录时，我一直收到错误。这个错误是什么意思？我做错了什么？

这是我的控制器动作：

public ActionResult Delete(int id)
{

    Person somePerson = db.People
        .Where(p => p.Id == id)     //this line says to find the person whose ID matches our parameter
        .FirstOrDefault();          //FirstOrDefault() returns either a singluar Person object or NULL

    db.Entry(somePerson).State = System.Data.Entity.EntityState.Deleted;
    db.SaveChanges();


    return View("Index");
}

这是我的观点：

@using sample.Models
@model List<Person>
@{

    Layout = null;
}

<!DOCTYPE html>

<html>
<head>
    <meta name="viewport" content="width=device-width" />
    <title>Index</title>
</head>
<body>
    <div> 
        <!-- Html.ActionLink is the MVC equivalent of <a href="..."></a>  
            -->
        @Html.ActionLink("Create new person", "Create")
        <table>
            <tr>
                <th></th>
                <th></th>
                <th>Email Address</th>
                <th>First Name</th>
                <th>Last Name</th>
            </tr>

            <!-- Loop through our List of People and create a new TR for each item -->
            @foreach(Person person in Model)  //Error Occurs on this line
            {
                <tr>
                    <td></td>
                    <td>@Html.ActionLink("Edit", "Edit", new { id = person.Id })</td>
                    <td>@Html.ActionLink("Delete", "Delete", new { id = person.Id })</td>
                    <!-- Using the @@ tag will inject the object's value into HTML -->
                    <td>@person.Email</td>
                    <td>@person.FirstName</td>
                    <td>@person.LastName</td>
                </tr>
            }
        </table>
    </div>
</body>
</html>

编辑和创建工作正常。当我添加删除是我开始得到问题的地方。这是我得到的例外，Model是null FYI

An exception of type 'System.NullReferenceException' occurred in App_Web_rczw3znb.dll but was not handled in user code

Answer 1

您需要为Index视图提供模型。您在Create和Edit中执行了此操作..但您不在Delete。

所以，像这样：

return View("Index", listOfPeopleHere);

此外，您似乎将View用作整个页面。您应该真正考虑使用Layout ..以便在每个视图中不需要页面顶部的样板代码。

Answer 2

    public ActionResult Delete(int id)
    {
        //Find the person in the DB.  Use the supplied "id" integer as a reference.
        Person somePerson = db.People
            .Where(p => p.Id == id)     //this line says to find the person whose ID matches our parameter
            .FirstOrDefault();          //FirstOrDefault() returns either a singluar Person object or NULL

        if (ModelState.IsValid)
        {
            db.People.Remove(somePerson);
            db.SaveChanges();
            return RedirectToAction("Index");
        }
        return View(somePerson);
    }

删除时模型空Null异常错误

2 个答案: