我正在尝试使用EF6更新记录。首先找到记录，如果存在，则更新它。这是我的代码： -
var book = new Model.Book
{
BookNumber = _book.BookNumber,
BookName = _book.BookName,
BookTitle = _book.BookTitle,
};
using (var db = new MyContextDB())
{
var result = db.Books.SingleOrDefault(b => b.BookNumber == bookNumber);
if (result != null)
{
try
{
db.Books.Attach(book);
db.Entry(book).State = EntityState.Modified;
db.SaveChanges();
}
catch (Exception ex)
{
throw;
}
}
}
每次我尝试使用上面的代码更新记录时，我收到此错误： -
{System.Data.Entity.Infrastructure.DbUpdateConcurrencyException：存储更新，插入或删除语句影响了意外的行数（0）。自实体加载后，实体可能已被修改或删除。刷新ObjectStateManager entrie
您正在尝试更新记录（对我而言，这意味着“更改现有记录上的值并将其保存回来”）。因此，您需要检索对象，进行更改并保存。
using (var db = new MyContextDB())
{
var result = db.Books.SingleOrDefault(b => b.BookNumber == bookNumber);
if (result != null)
{
result.SomeValue = "Some new value";
db.SaveChanges();
}
}
我发现了一种方法很好。
var Update = context.UpdateTables.Find(id);
Update.Title = title;
// Mark as Changed
context.Entry(Update).State = System.Data.Entity.EntityState.Modified;
context.SaveChanges();
这是我的后RIA实体更新方法（针对Ef6时间框架）：
public static void UpdateSegment(ISegment data)
{
if (data == null) throw new ArgumentNullException("The expected Segment data is not here.");
var context = GetContext();
var originalData = context.Segments.SingleOrDefault(i => i.SegmentId == data.SegmentId);
if (originalData == null) throw new NullReferenceException("The expected original Segment data is not here.");
FrameworkTypeUtility.SetProperties(data, originalData);
context.SaveChanges();
}
请注意，FrameworkTypeUtility.SetProperties()是我在NuGet上的AutoMapper之前编写的一个很小的实用函数：
public static void SetProperties<TIn, TOut>(TIn input, TOut output, ICollection<string> includedProperties)
where TIn : class
where TOut : class
{
if ((input == null) || (output == null)) return;
Type inType = input.GetType();
Type outType = output.GetType();
foreach (PropertyInfo info in inType.GetProperties())
{
PropertyInfo outfo = ((info != null) && info.CanRead)
? outType.GetProperty(info.Name, info.PropertyType)
: null;
if (outfo != null && outfo.CanWrite
&& (outfo.PropertyType.Equals(info.PropertyType)))
{
if ((includedProperties != null) && includedProperties.Contains(info.Name))
outfo.SetValue(output, info.GetValue(input, null), null);
else if (includedProperties == null)
outfo.SetValue(output, info.GetValue(input, null), null);
}
}
}
像Renat说的那样，删除：db.Books.Attach(book);
此外，将结果查询更改为使用“AsNoTracking”，因为此查询会丢弃实体框架的模型状态。它认为“结果”是现在要跟踪的书，你不希望这样。
var result = db.Books.AsNoTracking().SingleOrDefault(b => b.BookNumber == bookNumber);
试试吧....
的UpdateModel（书）;
var book = new Model.Book
{
BookNumber = _book.BookNumber,
BookName = _book.BookName,
BookTitle = _book.BookTitle,
};
using (var db = new MyContextDB())
{
var result = db.Books.SingleOrDefault(b => b.BookNumber == bookNumber);
if (result != null)
{
try
{
UpdateModel(book);
db.Books.Attach(book);
db.Entry(book).State = EntityState.Modified;
db.SaveChanges();
}
catch (Exception ex)
{
throw;
}
}
}
这适用于Entity Framework 6.2.0。
如果您有特定的DbSet和需要更新或创建的项目：
var name = getNameFromService();
var current = _dbContext.Names.Find(name.BusinessSystemId, name.NameNo);
if (current == null)
{
_dbContext.Names.Add(name);
}
else
{
_dbContext.Entry(current).CurrentValues.SetValues(name);
}
_dbContext.SaveChanges();
但是，这也可以用于具有单个主键或复合主键的通用DbSet。
var allNames = NameApiService.GetAllNames();
GenericAddOrUpdate(allNames, "BusinessSystemId", "NameNo");
public virtual void GenericAddOrUpdate<T>(IEnumerable<T> values, params string[] keyValues) where T : class
{
foreach (var value in values)
{
try
{
var keyList = new List<object>();
//Get key values from T entity based on keyValues property
foreach (var keyValue in keyValues)
{
var propertyInfo = value.GetType().GetProperty(keyValue);
var propertyValue = propertyInfo.GetValue(value);
keyList.Add(propertyValue);
}
GenericAddOrUpdateDbSet(keyList, value);
//Only use this when debugging to catch save exceptions
//_dbContext.SaveChanges();
}
catch
{
throw;
}
}
_dbContext.SaveChanges();
}
public virtual void GenericAddOrUpdateDbSet<T>(List<object> keyList, T value) where T : class
{
//Get a DbSet of T type
var someDbSet = Set(typeof(T));
//Check if any value exists with the key values
var current = someDbSet.Find(keyList.ToArray());
if (current == null)
{
someDbSet.Add(value);
}
else
{
Entry(current).CurrentValues.SetValues(value);
}
}
我知道它已经好几次回答了好，但是我喜欢这种方式。我希望它能帮助别人。
//attach object (search for row)
TableName tn = _context.TableNames.Attach(new TableName { PK_COLUMN = YOUR_VALUE});
// set new value
tn.COLUMN_NAME_TO_UPDATE = NEW_COLUMN_VALUE;
// set column as modified
_context.Entry<TableName>(tn).Property(tnp => tnp.COLUMN_NAME_TO_UPDATE).IsModified = true;
// save change
_context.SaveChanges();
我一直在审查实体框架的源代码，如果你知道Key属性，在其他情况下需要检查AddOrUpdate实现，我找到了实际更新实体的方法：
public void Update<T>(T item) where T: Entity
{
// assume Entity base class have an Id property for all items
var entity = _collection.Find(item.Id);
if (entity == null)
{
return;
}
_context.Entry(entity).CurrentValues.SetValues(item);
}
希望这有帮助！
您可以使用AddOrUpdate方法：
db.Books.AddOrUpdate(book); //requires using System.Data.Entity.Migrations;
db.SaveChanges();
因此，您有一个已更新的实体，并且您希望使用最少量的代码在数据库中更新它...
并发总是很棘手，但我假设你只是希望你的更新获胜。这是我为同一个案例做的事情，并修改名称来模仿你的类。换句话说，只需将attach更改为add，它对我有用：
public static void SaveBook(Model.Book myBook)
{
using (var ctx = new BookDBContext())
{
ctx.Books.Add(myBook);
ctx.Entry(myBook).State = System.Data.Entity.EntityState.Modified;
ctx.SaveChanges();
}
}
此代码是测试的结果，该测试仅更新一组列而不进行查询以首先返回记录。它首先使用Entity Framework 7代码。
// This function receives an object type that can be a view model or an anonymous
// object with the properties you want to change.
// This is part of a repository for a Contacts object.
public int Update(object entity)
{
var entityProperties = entity.GetType().GetProperties();
Contacts con = ToType(entity, typeof(Contacts)) as Contacts;
if (con != null)
{
_context.Entry(con).State = EntityState.Modified;
_context.Contacts.Attach(con);
foreach (var ep in entityProperties)
{
// If the property is named Id, don't add it in the update.
// It can be refactored to look in the annotations for a key
// or any part named Id.
if(ep.Name != "Id")
_context.Entry(con).Property(ep.Name).IsModified = true;
}
}
return _context.SaveChanges();
}
public static object ToType<T>(object obj, T type)
{
// Create an instance of T type object
object tmp = Activator.CreateInstance(Type.GetType(type.ToString()));
// Loop through the properties of the object you want to convert
foreach (PropertyInfo pi in obj.GetType().GetProperties())
{
try
{
// Get the value of the property and try to assign it to the property of T type object
tmp.GetType().GetProperty(pi.Name).SetValue(tmp, pi.GetValue(obj, null), null);
}
catch (Exception ex)
{
// Logging.Log.Error(ex);
}
}
// Return the T type object:
return tmp;
}
这是完整的代码：
public interface IContactRepository
{
IEnumerable<Contacts> GetAllContats();
IEnumerable<Contacts> GetAllContactsWithAddress();
int Update(object c);
}
public class ContactRepository : IContactRepository
{
private ContactContext _context;
public ContactRepository(ContactContext context)
{
_context = context;
}
public IEnumerable<Contacts> GetAllContats()
{
return _context.Contacts.OrderBy(c => c.FirstName).ToList();
}
public IEnumerable<Contacts> GetAllContactsWithAddress()
{
return _context.Contacts
.Include(c => c.Address)
.OrderBy(c => c.FirstName).ToList();
}
//TODO Change properties to lambda expression
public int Update(object entity)
{
var entityProperties = entity.GetType().GetProperties();
Contacts con = ToType(entity, typeof(Contacts)) as Contacts;
if (con != null)
{
_context.Entry(con).State = EntityState.Modified;
_context.Contacts.Attach(con);
foreach (var ep in entityProperties)
{
if(ep.Name != "Id")
_context.Entry(con).Property(ep.Name).IsModified = true;
}
}
return _context.SaveChanges();
}
public static object ToType<T>(object obj, T type)
{
// Create an instance of T type object
object tmp = Activator.CreateInstance(Type.GetType(type.ToString()));
// Loop through the properties of the object you want to convert
foreach (PropertyInfo pi in obj.GetType().GetProperties())
{
try
{
// Get the value of the property and try to assign it to the property of T type object
tmp.GetType().GetProperty(pi.Name).SetValue(tmp, pi.GetValue(obj, null), null);
}
catch (Exception ex)
{
// Logging.Log.Error(ex);
}
}
// Return the T type object
return tmp;
}
}
public class Contacts
{
public int Id { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
public string Email { get; set; }
public string Company { get; set; }
public string Title { get; set; }
public Addresses Address { get; set; }
}
public class Addresses
{
[Key]
public int Id { get; set; }
public string AddressType { get; set; }
public string StreetAddress { get; set; }
public string City { get; set; }
public State State { get; set; }
public string PostalCode { get; set; }
}
public class ContactContext : DbContext
{
public DbSet<Addresses> Address { get; set; }
public DbSet<Contacts> Contacts { get; set; }
public DbSet<State> States { get; set; }
protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
{
var connString = "Server=YourServer;Database=ContactsDb;Trusted_Connection=True;MultipleActiveResultSets=true;";
optionsBuilder.UseSqlServer(connString);
base.OnConfiguring(optionsBuilder);
}
}
你应该使用。如果要更新对象中的所有字段，请使用Entry（）方法。另请注意，您无法更改字段ID（键），因此在编辑时首先将Id设置为某些ID。
using(var context = new ...())
{
var EditedObj = context
.Obj
.Where(x => x. ....)
.First();
NewObj.Id = EditedObj.Id; //This is important when we first create an object (NewObj), in which the default Id = 0. We can not change an existing key.
context.Entry(EditedObj).CurrentValues.SetValues(NewObj);
context.SaveChanges();
}
以下是此问题的最佳解决方案：在视图中添加所有ID（密钥）。考虑有多个名为（第一，第二和第三）的表
@Html.HiddenFor(model=>model.FirstID)
@Html.HiddenFor(model=>model.SecondID)
@Html.HiddenFor(model=>model.Second.SecondID)
@Html.HiddenFor(model=>model.Second.ThirdID)
@Html.HiddenFor(model=>model.Second.Third.ThirdID)
在C＃代码中，
[HttpPost]
public ActionResult Edit(First first)
{
if (ModelState.Isvalid)
{
if (first.FirstID > 0)
{
datacontext.Entry(first).State = EntityState.Modified;
datacontext.Entry(first.Second).State = EntityState.Modified;
datacontext.Entry(first.Second.Third).State = EntityState.Modified;
}
else
{
datacontext.First.Add(first);
}
datacontext.SaveChanges();
Return RedirectToAction("Index");
}
return View(first);
}
using(var myDb = new MyDbEntities())
{
user user = new user();
user.username = "me";
user.email = "[email protected]";
myDb.Users.Add(user);
myDb.users.Attach(user);
myDb.Entry(user).State = EntityState.Modified;//this is for modiying/update existing entry
myDb.SaveChanges();
}
你应该删除db.Books.Attach(book);