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);
}
}
以下是我的后ria实体更新方法(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();
}
注意FrameworkTypeUtility.SetProperties()是我在NuGet上AutoMapper之前写的一个小工具函数:
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);
}
}
}