asp.net-mvc – 强大类型的ASP.NET MVC与ADO.NET实体框架

经过几天的斗争,我终于得到了这个工作.

我有一个简单的人员和部门数据库：

ADO.NET Entity Framework Entity Data Model diagram with Department and Person objects http://img39.imageshack.us/img39/1368/edmxdepartmentperson.gif

我可以使用强类型的ASP.NET MVC视图参考/导航属性！查看部门清单…

ASP.NET MVC with DropDownList http://img11.imageshack.us/img11/7619/dropdownlistdepartment.gif

我的人/编辑视图的一部分：

<% using (Html.BeginForm()) {%>
    <%= Html.Hidden("Id",Model.Id) %>
    <fieldset>
        <legend>Fields</legend>
        <p>
            <label for="Name">Name:</label>
            <%= Html.TextBox("Name",Model.Name) %>
        </p>
        <p>
            <label for="DepartmentId">Department:</label>
            <%= Html.DropDownList("DepartmentId",new SelectList((IEnumerable)ViewData["Departments"],"Id","Name"))%>
        </p>
        <p>
            <input type="submit" value="Save" />
        </p>
    </fieldset>
<% } %>

我的人员控制器的一部分：

//
// GET: /Person/Edit/5

public ActionResult Edit(Guid id)
{
    ViewData["Departments"] = ctx.Department;
    Person model = (from Person p in ctx.Person
                    where p.Id == id
                    select p).FirstOrDefault();
    return View(model);
}

//
// POST: /Person/Edit

[AcceptVerbs(HttpVerbs.Post)]
public ActionResult Edit(Person model)
{
    ctx.AttachUpdated(model);  //extension
    ctx.SaveChanges();
    return RedirectToAction("Index");
}

为了得到这个工作,我用一个新的DepartmentId属性扩展了Person EntityObject.

using System;
using System.Data;
using System.Data.Objects.DataClasses;

namespace ProjectName.Models
{
    public partial class Person : EntityObject
    {
        public Guid DepartmentId
        {
            get
            {
                try
                {
                    return (Guid)this.DepartmentReference.EntityKey.EntityKeyValues[0].Value;
                }
                catch
                {
                    return Guid.Empty;
                }
            }
            set
            {
                this.DepartmentReference.EntityKey = new EntityKey("JunkEntities.Department",value);
            }
        }
    }
}

并且我用新的AttachUpdated和ApplyReferencePropertyChanges方法扩展了Entity Framework ObjectContext：

using System;
using System.Data;
using System.Data.Objects;
using System.Data.Objects.DataClasses;

public static class EntityFrameworkExtensionMethods
{

    public static void AttachUpdated(this ObjectContext ctx,EntityObject objectDetached)
    {
        if (objectDetached.EntityKey == null)
        {
            String entitySetName = ctx.DefaultContainerName + "." + objectDetached.GetType().Name;
            Guid objectId = (Guid)objectDetached.GetType().GetProperty("Id").GetValue(objectDetached,null);
            objectDetached.EntityKey = new System.Data.EntityKey(entitySetName,objectId);
        }
        if (objectDetached.EntityState == EntityState.Detached)
        {
            object currentEntityInDb = null;
            if (ctx.TryGetObjectByKey(objectDetached.EntityKey,out currentEntityInDb))
            {
                ctx.ApplyPropertyChanges(objectDetached.EntityKey.EntitySetName,objectDetached);
                ctx.ApplyReferencePropertyChanges((IEntityWithRelationships)objectDetached,(IEntityWithRelationships)currentEntityInDb);  //extension
            }
            else
            {
                throw new ObjectNotFoundException();
            }
        }
    }

    public static void ApplyReferencePropertyChanges(this ObjectContext ctx,IEntityWithRelationships newEntity,IEntityWithRelationships oldEntity)
    {
        foreach (var relatedEnd in oldEntity.RelationshipManager.GetAllRelatedEnds())
        {
            var oldRef = relatedEnd as EntityReference;
            if (oldRef != null)
            {
                var newRef = newEntity.RelationshipManager.GetRelatedEnd(oldRef.RelationshipName,oldRef.TargetRoleName) as EntityReference;
                oldRef.EntityKey = newRef.EntityKey;
            }
        }
    }

}

我只想记录我在这里的进度.请建议改进.

谢谢：

> Alex James
> Cesar de la Torre
> Griff Townsend
> Steve Willcock
> jrista
> Tomas Lycken
> Thomas Levesque
> Danny Simmons
> Stefan Cruysberghs

解决方法

我不喜欢将这个新属性添加到实体框架上的部分类中,因为它不允许有太多变化.
尝试标记你的Deparment DropDown“Department.Id”这样

<p>
    <label for="Department.Id">Department:</label>
<%= Html.DropDownList("Department.Id","Name"))%>
</p>

MVC框架的ModelBinding将获取该值并将其应用于“部门”导航属性的“Id”属性.我发现部门的其他价值是空的,但这并不重要.现在,您有一种方法来检索正确的部门实体并将其应用于在“绑定到您的Action”参数中创建的新Person实体的部门导航属性,如下所示：

newPerson.Department = ctx.Department.First(d => d.DepartmentId == newPerson.Department.Id);

这样做,您不需要更新您的实体,因为它应该具有的属性.

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