C# 实体框架集合被修改；枚举操作可能不会执行
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Entity Framework Collection was modified; enumeration operation may not execute
提问by madatanic
I'm currently using EF 4.0. My objective is to delete a child collection and add new ones to same parent.
我目前正在使用 EF 4.0。我的目标是删除一个子集合并将新集合添加到同一个父集合。
public void AddKids(int parentId, Kids newKids)
{
using (ModelContainer context = new ModelContainer(connectionString))
{
using (TransactionScope scope = new TransactionScope())
{
var query = from Parent _parent in context.Parents
where _parent.ParentId == parentId select _parent;
Parent parent = query.Single();
while (parent.Kids.Any())
{
context.Kids.DeleteObject(parent.Kids.First());
}
if (newKids != null)
{
foreach (Kid _kid in newKids)
{
parent.Kids.Add(new Kid
{
Age = _kid.Age,
Height = _kid.Height
});
}
}
scope.Complete();
}
context.SaveChanges(); //Error happens here
}
}
The error is as from the title: Collection was modified; enumeration operation may not execute.
错误来自标题：Collection was modified; 枚举操作可能无法执行。
Any help would be appreciated.
任何帮助，将不胜感激。
采纳答案by ScorpiAS
You are seeing this because you delete objects from a collection that currently has active operations on. More specifically you are updating the Kids collection and then executing the Any() operator on it in the while loop. This is not a supported operation when working with IEnumerable instances. What I can advice you to do is rewrite your while as this:
您之所以看到这一点，是因为您从当前具有活动操作的集合中删除了对象。更具体地说，您正在更新 Kids 集合，然后在 while 循环中对其执行 Any() 运算符。使用 IEnumerable 实例时，这不是受支持的操作。我可以建议您做的是将您的 while 改写为：
parent.Kids.ToList().ForEach(r => context.Kids.DeleteObject(r));
I hope that helps.
我希望这有帮助。
