我正在尝试使用EF6更新记录。首先找到记录，如果它存在，则更新。
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，我都会得到这个错误:
{System.Data.Entity.Infrastructure。DbUpdateConcurrencyException:存储
更新、插入或删除语句受影响的数量超出预期
自实体以来，实体可能已被修改或删除
被加载。刷新ObjectStateManager条目
这是实体框架6.2.0。
如果你有一个特定的DbSet和一个需要更新或创建的项:
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);
}
}
Not related to this specific example, but I came across a challenge when trying to use EF and a DateTime field as the concurrency check field. It appears the EF concurrency code doesn't honor the precision setting from the metadata (edmx) i.e. Type="DateTime" Precision="3".
The database datetime field will store a millisecond component within the field (i.e. 2020-10-18 15:49:02.123). Even if you set the original value of the Entity to a DateTime that includes the millisecond component, the SQL EF generates is this:
UPDATE [dbo].[People]
SET [dateUpdated] = @0
WHERE (([PeopleID] = @1) AND ([dateUpdated] = @2))
-- @0: '10/19/2020 1:07:00 AM' (Type = DateTime2)
-- @1: '3182' (Type = Int32)
-- @2: '10/19/2020 1:06:10 AM' (Type = DateTime2)
正如您所看到的，@2是一个没有毫秒组件的STRING表示。这将导致更新失败。
因此，如果您打算使用DateTime字段作为并发键，那么在检索记录时必须从数据库字段中剥离毫秒/ tick，并且仅使用类似剥离的DateTime传递/更新字段。
//strip milliseconds due to EF concurrency handling
PeopleModel p = db.people.Where(x => x.PeopleID = id);
if (p.dateUpdated.Millisecond > 0)
{
DateTime d = new DateTime(p.dateUpdated.Ticks / 10000000 * 10000000);
object[] b = {p.PeopleID, d};
int upd = db.Database.ExecuteSqlCommand("Update People set dateUpdated=@p1 where peopleId=@p0", b);
if (upd == 1)
p.dateUpdated = d;
else
return InternalServerError(new Exception("Unable to update dateUpdated"));
}
return Ok(p);
当用新值更新字段时，也去掉毫秒
(param)int id, PeopleModel person;
People tbl = db.People.Where(x => x.PeopleID == id).FirstOrDefault();
db.Entry(tbl).OriginalValues["dateUpdated"] = person.dateUpdated;
//strip milliseconds from dateUpdated since EF doesn't preserve them
tbl.dateUpdated = new DateTime(DateTime.Now.Ticks / 10000000 * 10000000);
这是实体框架6.2.0。
如果你有一个特定的DbSet和一个需要更新或创建的项:
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);
}
}
这里是这个问题的最佳解决方案:在视图中添加所有的ID(键)。考虑将多个表命名为(First, Second和Third)
@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);
}
