如何检查集合的两个实体项是否相同
本文关键字:实体 两个 是否 何检查 检查 集合 | 更新日期: 2023-09-27 17:54:01
我试图做一个通用的方法来更新实体框架集合,一对多。我做了这个方法,但我有一个问题,当我试图验证,如果在新集合中的元素已经存在于旧的。如果存在,我必须更新它,而不是删除并重新添加。
代码如下:
public TEntity UpdateCollection<TEntity, TChildren>(myappContext dbContext, TEntity parentObject, Expression<Func<TEntity,
ICollection<TChildren>>> propertyExpression, ICollection<TChildren> objectChilren) where TEntity : class where TChildren : class
{
var parentEntityObject = dbContext.Entry<TEntity>(parentObject);
List<TChildren> originalChildrenData = parentEntityObject.Collection(propertyExpression).CurrentValue.ToList();
// Updating or removing existing items
foreach (var originalItem in originalChildrenData)
{
// Where the problem is: If entry was just modified, i have to update.
var newItem = objectChilren.FirstOrDefault(x => x == originalItem);
if (newItem != null)
{
dbContext.Entry<TChildren>(originalItem).CurrentValues.SetValues(newItem);
dbContext.Entry<TChildren>(originalItem).State = System.Data.EntityState.Modified;
}
else
{
dbContext.Entry<TChildren>(originalItem).State = System.Data.EntityState.Deleted;
}
}
// Adding new items
foreach(var newItem in objectChilren.Except(originalChildrenData)){
parentEntityObject.Collection(propertyExpression).CurrentValue.Add(newItem);
}
parentEntityObject.State = System.Data.EntityState.Modified;
return parentEntityObject.Entity;
}
而不是尝试检查:
var newItem = objectChilren.FirstOrDefault(x => x == originalItem);
if (newItem != null)
我还尝试了:
var newItem = this.Set<TChildren>().Local.FirstOrDefault(x => x == originalItem);
但是也不工作,总是返回null。我必须得到相应的条目,并且只更新它。
如果这是不可能的,有另一种通用的方式来更新集合"一对多"?
我这样做了,比较了我的集合中的key属性,就像Magnus建议的那样,像这样:
public TEntity UpdateCollection<TEntity, TChildren>(myappContext dbContext, TEntity parentObject, Expression<Func<TEntity,
ICollection<TChildren>>> propertyExpression, ICollection<TChildren> objectChilren) where TEntity : class where TChildren : class
{
var parentEntityObject = dbContext.Entry<TEntity>(parentObject);
List<TChildren> originalChildrenData = parentEntityObject.Collection(propertyExpression).CurrentValue.ToList();
// Get key name
var entityKeyName = GetKeyName(dbContext, originalChildrenData.Union(objectChilren).First());
// Updating or removing existing items
foreach (var originalItem in originalChildrenData)
{
var originalValueKey = originalItem.GetType().GetProperty(entityKeyName).GetValue(originalItem, null);
var itemCompareExpression = GetCompareExpression<TChildren>(entityKeyName, originalValueKey);
// If entry was just modified, i have to update.
var newItem = objectChilren.FirstOrDefault(itemCompareExpression.Compile());
if (newItem != null)
{
dbContext.Entry<TChildren>(originalItem).CurrentValues.SetValues(newItem);
dbContext.Entry<TChildren>(originalItem).State = System.Data.EntityState.Modified;
// Remove item, because only 'new items' will be added after this loop
objectChilren.Remove(newItem);
}
else
{
dbContext.Entry<TChildren>(originalItem).State = System.Data.EntityState.Deleted;
}
}
// Adding new items
foreach(var newItem in objectChilren)
{
parentEntityObject.Collection(propertyExpression).CurrentValue.Add(newItem);
}
parentEntityObject.State = System.Data.EntityState.Modified;
return parentEntityObject.Entity;
}
方法称为:
public string GetKeyName<TEntity>(myappContext dbContext, TEntity entity) where TEntity : class
{
ObjectContext objectContext = ((IObjectContextAdapter)dbContext).ObjectContext;
ObjectSet<TEntity> set = objectContext.CreateObjectSet<TEntity>();
return set.EntitySet.ElementType.KeyMembers.FirstOrDefault().Name;
}
public Expression<Func<TEntity, bool>> GetCompareExpression<TEntity>(string keyName, object value) where TEntity : class
{
var parameter = Expression.Parameter(typeof(TEntity), "x");
var property = Expression.Property(parameter, keyName);
var method = property.Type.GetMethod("Equals", new[] { property.Type });
var convertedValue = Convert.ChangeType(value, property.Type);
var expression = Expression.Call(property, method, Expression.Constant(convertedValue));
return Expression.Lambda<Func<TEntity, bool>>(expression, parameter);
}
由于我所有的实体只有一个键,我只是在"GetKeyName"上使用"First",但它返回所有键,如有必要