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[英]How to recursively check if the entity has a collection of children of that same entity?
[英]How to check if two entity entries of a collection are the same
我試圖做一個通用的方法來更新實體框架集合,一對多。 我做了這種方法,但是當我嘗試驗證新集合中的元素是否已經存在於舊集合中時,我遇到了問題。 如果存在,我必須對其進行更新,而不是刪除並再次添加。
代碼是這樣的:
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;
}
而不是嘗試檢查:
var newItem = objectChilren.FirstOrDefault(x => x == originalItem);
if (newItem != null)
我也嘗試過:
var newItem = this.Set<TChildren>().Local.FirstOrDefault(x => x == originalItem);
但也不起作用,總是返回null。 我必須獲取相應的條目並僅對其進行更新。
如果不可能,還有另一種通用的方法可以“一對多”更新集合嗎?
我做到了,就像Magnus所建議的那樣,比較了我收藏中的關鍵屬性,如下所示:
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;
}
方法稱為:
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);
}
由於我所有的實體只有一個鍵,因此我只在“ GetKeyName”上使用了“ First”,但如有必要,它將返回所有鍵。
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