我有两个班级：
public partial class ObjectiveDetail {
public ObjectiveDetail() {
this.SubTopics = new List<SubTopic>();
}
public int ObjectiveDetailId { get; set; }
public int Number { get; set; }
public string Text { get; set; }
public virtual ICollection<SubTopic> SubTopics { get; set; }
}
public partial class SubTopic {
public int SubTopicId { get; set; }
public string Name { get; set; }
}
我有一个来自用户的ObjectiveDetail对象：
var web = {
"objectiveDetailId":1,
"number":1,
"text":"datafromweb",
"subTopics":[
{"subTopicId":1,
"name":"one"
},
{"subTopicId":3,
"name":"three",
}
]
}
来自数据库的ObjectiveDetail：
var db = {
"objectiveDetailId":1,
"number":1,
"text":"datafromdb",
"subTopics":[
{"subTopicId":1,
"name":"one"
},
{"subTopicId":2,
"name":"two",
}
]
}
使用Entity Framework 6我知道我可以使用：
更新ObjectiveDetail类中的文本_uow.ObjectiveDetails.Update(web));
但是如何在连接这两个表的多对多表中更新对ObjectiveDetail和SubTopics的引用。这里例如我想要它，以便对于ObjectiveDetail 1，将many-many更改为引用subTopicId 1和3而不是值1和2.请注意，ObjectiveDetail和SubTopic存储在表中，并且它们之间有另一个表。这是DDL：
CREATE TABLE [dbo].[ObjectiveDetail] (
[ObjectiveDetailId] INT IDENTITY (1, 1) NOT NULL,
[Text] NVARCHAR (MAX) NOT NULL,
[ObjectiveTopicId] INT NULL,
CONSTRAINT [PK_ObjectiveDetail] PRIMARY KEY CLUSTERED ([ObjectiveDetailId] ASC),
);
CREATE TABLE [dbo].[ObjectiveTopic] (
[ObjectiveDetailId] INT NOT NULL,
[SubTopicId] INT NOT NULL,
CONSTRAINT [FK_ObjectiveTopicObjectiveDetail] FOREIGN KEY ([ObjectiveDetailId]) REFERENCES [dbo].[ObjectiveDetail] ([ObjectiveDetailId]),
CONSTRAINT [FK_ObjectiveTopicSubTopic] FOREIGN KEY ([SubTopicId]) REFERENCES [dbo].[SubTopic] ([SubTopicId])
);
CREATE TABLE [dbo].[SubTopic] (
[SubTopicId] INT IDENTITY (1, 1) NOT NULL,
[Name] NVARCHAR (150) NOT NULL,
CONSTRAINT [PK_SubTopic] PRIMARY KEY CLUSTERED ([SubTopicId] ASC),
);
这是我的EF Mapping：
public class ObjectiveDetailMap : EntityTypeConfiguration<ObjectiveDetail>
{
public ObjectiveDetailMap()
{
// Primary Key
this.HasKey(t => t.ObjectiveDetailId);
// Relationships
this.HasMany(t => t.SubTopics)
.WithMany(t => t.ObjectiveDetails)
.Map(m =>
{
m.ToTable("ObjectiveTopic");
m.MapLeftKey("ObjectiveDetailId");
m.MapRightKey("SubTopicId");
});
}
}
答案 0 :(得分：7)
我认为您正在尝试模拟为您的用户工作的离线模式。因此，当您从用户那里获得某些内容时，您希望将数据库与用户数据同步。我做了一个例子，把你的问题提高了一步:)我添加了一个需要在数据库中更新的Subtopic。好的是代码：
static void Main(string[] args)
{
//the database
var ObjectiveDetails = new List<ObjectiveDetail>()
{
new ObjectiveDetail()
{
ObjectiveDetailId = 1,
Number = 1,
Text = "datafromdb",
SubTopics = new List<SubTopic>()
{
new SubTopic(){ SubTopicId = 1, Name="one"}, //no change
new SubTopic(){ SubTopicId = 2, Name="two"}, //to be deleted
new SubTopic(){ SubTopicId = 4, Name="four"} //to be updated
}
}
};
//the object comes as json and serialized to defined object.
var web = new ObjectiveDetail()
{
ObjectiveDetailId = 1,
Number = 1,
Text = "datafromweb",
SubTopics = new List<SubTopic>()
{
new SubTopic(){ SubTopicId = 1, Name="one"}, //no change
new SubTopic(){ SubTopicId = 3, Name="three"}, //new row
new SubTopic(){ SubTopicId = 4, Name="new four"} //must be updated
}
};
var objDet = ObjectiveDetails.FirstOrDefault(x => x.ObjectiveDetailId == web.ObjectiveDetailId);
if (objDet != null)
{
//you can use AutoMapper or ValueInjecter for mapping and binding same objects
//but it is out of scope of this question
//update ObjectDetail
objDet.Number = web.Number;
objDet.Text = web.Text;
var subtops = objDet.SubTopics.ToList();
//Delete removed parameters from database
//Entity framework can handle it for you via change tracking
//subtopicId = 2 has been deleted
subtops.RemoveAll(x => !web.SubTopics.Select(y => y.SubTopicId).Contains(x.SubTopicId));
//adds new items which comes from web
//adds subtopicId = 3 to the list
var newItems = web.SubTopics.Where(x => !subtops.Select(y => y.SubTopicId).Contains(x.SubTopicId)).ToList();
subtops.AddRange(newItems);
//this items must be updated
var updatedItems = web.SubTopics.Except(newItems).ToList();
foreach (var item in updatedItems)
{
var dbItem = subtops.First(x => x.SubTopicId == item.SubTopicId);
dbItem.Name = item.Name;
}
//let's see is it working
Console.WriteLine("{0}:\t{1}\t{2}\n---------",objDet.ObjectiveDetailId, objDet.Number, objDet.Text);
foreach (var item in subtops)
{
Console.WriteLine("{0}: {1}", item.SubTopicId, item.Name);
}
}
else
{
//insert new ObjectiveDetail
}
//In real scenario after doing everything you need to call SaveChanges or it's equal in your Unit of Work.
}
结果：
1: 1 datafromweb
---------
1: one
4: new four
3: three
就是这样。您可以像这样同步数据库和用户数据。而且AutoMapper和ValueInjecter都是非常有用和强大的工具，我建议你去看看它们。我希望你喜欢，快乐的编码：）
答案 1 :(得分：6)
以下是一种方法，可以将目标ObjectiveDetail的ID和IEnumerable<int>个SubTopic个ID添加到目标ObjectiveDetail。
public void UpdateSubTopics( int objectiveDetailId, IEnumerable<int> newSubTopicIds )
{
using( var db = new YourDbContext() )
{
// load SubTopics to add from DB
var subTopicsToAdd = db.SubTopics
.Where( st => newSubTopicIds.Contains( st.SubTopicId ) );
// load target ObjectiveDetail from DB
var targetObjDetail = db.ObjectiveDetail.Find( objectiveDetailId );
// should check for targetObjDetail == null here
// remove currently referenced SubTopics not found in subTopicsToAdd
foreach( var cst in targetObjDetail.SubTopics.Except( subTopicsToAdd ) )
{
cst.SubTopics.Remove( cst );
}
// add subTopicsToAdd not currently found in referenced SubTopics
foreach( var nst in subTopicsToAdd.Except( targetObjDetail.SubTopics ) )
{
targetObjDetail.SubTopics.Add( nst );
}
// save changes
db.SaveChanges();
}
}
答案 2 :(得分：3)
我只使用EF代码优先，并定义3个表，您可以定义所有3个表，或者您只需定义2个表，每个表都有一个集合，如下所示
public class ObjectiveDetail
{
public ObjectiveDetail() {
this.SubTopics = new HashSet<SubTopic>();
}
public int ObjectiveDetailId { get; set; }
public int Number { get; set; }
public string Text { get; set; }
public virtual ICollection<SubTopic> SubTopics { get; set; }
}
public partial class SubTopic
{
public SubTopic() {
this.ObjectiveDetail = new HashSet<ObjectiveDetail>();
}
public int SubTopicId { get; set; }
public string Name { get; set; }
public virtual ICollection<ObjectiveDetail> ObjectiveDetails { get; set; }
}
如果您有3个表，则可以轻松地使用新的ID更新中间表。您必须获取要更新的所有ObjectiveTopics，并更改ID，然后执行更新
ObjectiveTopic objectiveTopic = _uow.ObjectiveTopic.Get(1);
ObjectiveTopic.SubTopicId = 2;
ObjectiveTopic.ObjectiveDetailId = 1;
_uow.ObjectiveTopic.Update(objectiveTopic);
如果您没有将第三个表定义为实体，并且您只能访问ObjectiveDetail和SubTopic表，那么您可以获取两个实体并删除不再需要的实体，并添加你想要的那个。
ObjectiveDetail objectiveD = _uow.ObjectiveDetail.Get(1);
SubTopic subTopic = _uow.SubTopic.Get(1); //SubTopic to remove
SubTopic topicToAdd = _uow.SubTopic.Get(2); //SubTopic to add
ObjectiveDetail.SubTopics.Remove(subTopic); //Remove the entity from the ObjectiveTopic table
ObjectiveDetail.SubTopics.Add(topicToAdd); //Add the new entity, will create a new row in ObjectiveTopic Table
_uow.ObjectiveDetail.Update(objectiveD);
如果你想（也许应该），你可以在objectiveD上使用linq从集合中获取实体，而不是从数据库中检索它。
SubTopic subTopic = objectiveD.SubTopics.Single(x => x.SubTopicId == 1); //Instead of _uow.SubTopic.Get(1);
...
答案 3 :(得分：0)
您可以使用通用方法，以便它可以用于任何多对多关系。您只需在主对象的多对多集合中提供此整数列表，表示要更新的字段的ID：
protected void UpdateManyToMany<T>(YourDBContext db, ICollection<T> collection, List<int> idList) where T : class
{
//update a many to many collection given a list of key IDs
collection.Clear();
var source = db.Set<T>();
if (idList != null)
{
foreach (int i in idList)
{
var record = source.Find(i);
collection.Add(record);
}
}
}
你会这样称呼：
UpdateManyToMany(db, objectiveDetail.SubTopics, subTopicIDList);