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);
}
}
这段代码是一个测试的结果，该测试只更新了一组列，而没有首先进行查询以返回记录。它首先使用实体框架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;
}
以下是完整的代码:
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);
}
}
