我使用EF4的经验非常有限。 我成功地从处于分离状态的Web服务反序列化实体，现在我想保存到数据库。 使用SaveChanges时，我得到以下异常：
System.Data.UpdateException：更新时发生错误 条目。有关详细信息，请参阅内部异常---＆GT; System.Data.SqlClient.SqlException：违反PRIMARY KEY 约束＆＃39; [主键约束名称]＆＃39;。无法插入重复 密钥对象＆＃39; [相关表名]＆＃39;。重复键值为（1）。 声明已经终止。
我尝试保存的实体将相关实体作为属性和属性，这些属性是实体的集合。
来自Web服务的ID用作表的主键，因此不会使用自动生成的ID。
以下测试说明了我试图解决的问题：
[TestMethod]
public void SaveRelatedDetachedEntitiesWithoutDuplicatesTest(){
using (var db = ProductEntities()){
//testing pre-saved existing category
if (!db.CategoryGroups.Any(e => e.Id == 3)){
db.CategoryGroups.AddObject(new Database.CategoryGroupEntity(){
Id = 3,
Name = "test group 3"
});
db.SaveChanges();
}
var categoryList = new List<CategoryEntity>(){
new CategoryEntity(){
Id = 1,
Name = "test category 1",
Groups = new List<CategoryGroupEntity> (){new CategoryGroupEntity(){
Id = 1,
Name = "test group 1"
},//duplicate
new CategoryGroupEntity(){
Id = 2,
Name = "test group 2"
}
}
},
new CategoryEntity(){
Id = 2,
Name = "test category 2",
Groups = new List<CategoryGroupEntity>{
new CategoryGroupEntity(){
Id = 1,
Name = "test group 1"
},//duplicate
new CategoryGroupEntity(){
Id = 3,
Name = "test group 3"
}//already in db
}
}
};
var product = new ProductEntity(){
Categories = categoryList,
Id = 1,
Name = "test product 1",
Type = new TypeEntity { Id = 1, Name = "test type" }
};
//all above code cannot be altered as it reflects what results from the deserialization.
db.Products.AddObject(product);
//need code here to handle the duplicates
db.SaveChanges();
var test = db.Products.Where(e => e.Id == 1).FirstOrDefault();
Assert.IsNotNull(test);
Assert.IsTrue(test.Categories.Count() == 2, "missing categories from product");
Assert.IsTrue(test.Categories.ElementAt(0).Groups.Any(e => e.Id == 1), "missing group from category 1");
Assert.IsTrue(test.Categories.ElementAt(1).Groups.Any(e => e.Id == 1), "missing group from category 2");
}
}
感谢您的帮助。
修改 我可以使用以下代码获取重复的组列表
var added = db.ObjectStateManager.GetObjectStateEntries(System.Data.EntityState.Added)
.Where(e => !e.IsRelationship).Select(e => e.Entity)
.OfType<CategoryGroupEntity>();
var duplicates = added.GroupBy(e => e.Id)
.Where(g => g.Count() > 1)
.SelectMany(g => g.Where(e => e != g.First())
我尝试但没有奏效的事情：
- 与状态未更改的数据上下文重复的实体。 因为附加一个CategoryGroupEntity导致所有相关实体被附加重复密钥问题仍然是
- 从Categories集合中移除实体实例并将其替换为首次创建的CategoryGroupEntity实例会导致同样的问题
- 删除重复的实体实例会导致第二个类别丢失组ID 1
作为旁注，当数据库中已存在特定的CategoryGroupEntity并尝试保存具有相同ID的实体时，我还需要避免重复密钥问题。
因此，当具有该ID的实体同时存在于数据库中或处于ObjectStateManager中的添加状态时，我需要避免重复键问题。 上面包含的测试包括两种情况。
答案 0 :(得分：0)
在实体框架中，如果您要添加的实体已经存在，那么只是给它的主键不起作用，您需要加载该实体并分配它
var product = new ProductEntity(){
Categories = categoryList,
Id = 1,
Name = "test product 1",
Type = new TypeEntity { Id = 1, Name = "test type" }
};
因此，在您的代码中，例如，Id = 1的TypeEntity已经存在，那么您需要将上面的代码更改为
var product = new ProductEntity(){
Categories = categoryList,
Id = 1,
Name = "test product 1",
Type = db.TypeEntity.Find(1);
};
EF适用于对象，所以为了说明你没有修改那个对象，而只是将它用作关系，你需要找到该对象并将其分配到你想要使用的位置。
更新类似的东西，例如
public class Princess
{
public int Id { get; set; }
public string Name { get; set; }
public virtual ICollection<Unicorn> Unicorns { get; set; }
}
var princess = context.Princesses.Find（#id）;
// Load the unicorns related to a given princess using a string to
// specify the relationship
context.Entry(princess).Collection("Unicorns").Load();
答案 1 :(得分：0)
我得到了它，但它绝对不是最好的方法。
我使用的保存方法包含在下面：
public static void SaveProduct(ProductEntity product) {
using (var db = ProductEntities()) {
//stored references to duplicate entities added to the objectContext
var duplicateGroupsAdded = new List<Tuple<CategoryEntity, GroupEntity>>();
var duplicateCategoriesAdded = new List<Tuple<ProductEntity, CategoryEntity>>();
//using existing instace of entities includes associated parent into db update causing duplicate product insert attempt.
//entities saved must be newly instantiated with no existing relationships.
var categories = product.Categories.ToList();
var type = new TypeEntity() {
Id = product.Type.Id,
Name = product.Type.Name
};
//empty the collection
product.Categories.ToList().ForEach(category => {
product.Categories.Remove(category);
});
//start off with clean product that we can populate with related entities
product.Type = null;
product.Group = null;
//add to db
db.Products.AddObject(product);
categories.ForEach(oldCategory => {
//new cloned category free of relationships
var category = new CategoryEntity() {
Id = oldCategory.Id,
Name = oldCategory.Name
};
//copy accross Groups as clean entities free of relationships
foreach (var group in oldCategory.Groups) {
category.Groups.Add(new GroupEntity() {
Id = group.Id,
Name = group.Name
});
}
//if the cat is alreay in the db use reference to tracked entity pulled from db
var preexistingCategory = db.Categories.SingleOrDefault(e => e.Id == category.Id);
if (preexistingCategory != null)
product.Categories.Add(preexistingCategory);
else {
//category not in database, create new
var Groups = category.Groups.ToList();
category.Groups.ToList().ForEach(group => category.Groups.Remove(group));
Groups.ForEach(Group => {
//if the group is alreay in the db use reference to tracked entity pulled from db
var preexistingGroup = db.Groups.SingleOrDefault(e => e.Id == Group.Id);
if (preexistingGroup != null)
category.Groups.Add(preexistingGroup);
else
category.Groups.Add(Group);
});
product.Categories.Add(category);
}
});
//if the type is alreay in the db use reference to tracked entity pulled from db
var preexistingType = db.Types.SingleOrDefault(e => e.Id == type.Id);
if (preexistingType != null)
product.Type = preexistingType;
else
product.Type = type;
//get lists of entities that are to be added to the database, and have been included in the update more than once (causes duplicate key error when attempting to insert).
var EntitiesToBeInserted = db.ObjectStateManager.GetObjectStateEntries(System.Data.EntityState.Added)
.Where(e => !e.IsRelationship).Select(e => e.Entity).ToList();
var duplicateGroupInsertions = EntitiesToBeInserted
.OfType<GroupEntity>()
.GroupBy(e => e.Id)
.Where(g => g.Count() > 1)
.SelectMany(g => g.Where(e => e != g.First()));
var duplicateCategoryInsertions = EntitiesToBeInserted
.OfType<CategoryEntity>()
.GroupBy(e => e.Id)
.Where(g => g.Count() > 1)
.SelectMany(g => g.Where(e => e != g.First()));
foreach (var category in product.Categories) {
//remove duplicate insertions and store references to add back in later
var joinedGroups = duplicateGroupInsertions.Join(category.Groups, duplicateGroupInsertion => duplicateGroupInsertion, linkedGroup => linkedGroup, (duplicateGroupInsertion, linkedGroup) => duplicateGroupInsertion);
foreach (var duplicateGroupInsertion in joinedGroups) {
if (category.Groups.Contains(duplicateGroupInsertion)) {
category.Groups.Remove(duplicateGroupInsertion);
db.Groups.Detach(duplicateGroupInsertion);
duplicateGroupsAdded.Add(new Tuple<CategoryEntity, GroupEntity>(category, duplicateGroupInsertion));
}
}
}
//remove duplicate insertions and store references to add back in later
var joinedCategories = duplicateCategoryInsertions.Join(product.Categories, duplicateCategoryInsertion => duplicateCategoryInsertion, linkedCategory => linkedCategory, (duplicateCategoryInsertion, linkedCategory) => duplicateCategoryInsertion);
foreach (var duplicateCategoryInsertion in joinedCategories) {
if (product.Categories.Contains(duplicateCategoryInsertion)) {
product.Categories.Remove(duplicateCategoryInsertion);
db.Categories.Detach(duplicateCategoryInsertion);
duplicateCategoriesAdded.Add(new Tuple<ProductEntity, CategoryEntity>(product, duplicateCategoryInsertion));
}
}
db.SaveChanges();
//entities not linked to product can now be added using references to the entities stored earlier
foreach (var duplicateGroup in duplicateGroupsAdded) {
var existingCategory = db.Categories.SingleOrDefault(e => e.Id == duplicateGroup.Item1.Id);
var existingGroup = db.Groups.SingleOrDefault(e => e.Id == duplicateGroup.Item2.Id);
existingCategory.Groups.Add(existingGroup);
}
foreach (var duplicateCategory in duplicateCategoriesAdded) {
product = db.Products.SingleOrDefault(e => e.Id == duplicateCategory.Item1.Id);
var existingCategory = db.Categories.SingleOrDefault(e => e.Id == duplicateCategory.Item2.Id);
product.Categories.Add(existingCategory);
}
db.SaveChanges();
}
}
欢迎任何进一步的建议