调用的UpdateModel具有复杂数据类型的集合重置所有非约束值? [英] Calling UpdateModel with a collection of complex data types reset all non-bound values?
问题描述
我不知道这是否是在DefaultModelBinder类或什么错误。
但通常的UpdateModel不改变,除了它找到了一个匹配的那些模型的任意值。
在下面一起来看看:
I'm not sure if this is a bug in the DefaultModelBinder class or what. But UpdateModel usually doesn't change any values of the model except the ones it found a match for. Take a look at the following:
[AcceptVerbs(HttpVerbs.Post)]
public ViewResult Edit(List<int> Ids)
{
// Load list of persons from the database
List<Person> people = GetFromDatabase(Ids);
// shouldn't this update only the Name & Age properties of each Person object
// in the collection and leave the rest of the properties (e.g. Id, Address)
// with their original value (whatever they were when retrieved from the db)
UpdateModel(people, "myPersonPrefix", new string[] { "Name", "Age" });
// ...
}
会发生什么事是创造的UpdateModel 新 Person对象,分配他们的姓名和放大器;从ValueProvider时代性,并把它们在参数列表&LT;>,这使得设置为默认的初始值的属性的其余部分(例如ID = 0)
那么,什么是怎么回事?
What happens is UpdateModel creates new Person objects, assign their Name & Age properties from the ValueProvider and put them in the argument List<>, which makes the rest of the properties set to their default initial value (e.g. Id = 0) so what is going on here?
推荐答案
更新:
我通过MVC源码code(尤其是 DefaultModelBinder
类),并在这里踩是我发现:
UPDATE:
I stepped through mvc source code (particularly DefaultModelBinder
class) and here is what I found:
类决定了我们正在努力使其调用方法绑定集合: UpdateCollection(...)
这将创建一个内部 ModelBindingContext
具有空
模式
属性。此后,这种情况下被发送到检查模式
属性<$ c中的方法 BindComplexModel(...)
$ C>空并创建一个新模型类型的实例,如果是这样的情况。
The class determines we are trying to bind a collection so it calls the method: UpdateCollection(...)
which creates an inner ModelBindingContext
that has a null
Model
property. Afterwards, that context is sent to the method BindComplexModel(...)
which checks the Model
property for null
and creates a new instance of the model type if that is the case.
这是什么原因造成的值复位。
That's what causes the values to be reset.
所以,填充只有通过形式/查询字符串/路由数据里的值,其余保持其初始状态。
And so, only the values that are coming through the form/query string/route data are populated, the rest remains in its initialized state.
我能够做很少修改 UpdateCollection(...)
来解决这个问题。
I was able to make very few changes to UpdateCollection(...)
to fix this problem.
下面是我的变化方法:
internal object UpdateCollection(ControllerContext controllerContext, ModelBindingContext bindingContext, Type elementType) {
IModelBinder elementBinder = Binders.GetBinder(elementType);
// build up a list of items from the request
List<object> modelList = new List<object>();
for (int currentIndex = 0; ; currentIndex++) {
string subIndexKey = CreateSubIndexName(bindingContext.ModelName, currentIndex);
if (!DictionaryHelpers.DoesAnyKeyHavePrefix(bindingContext.ValueProvider, subIndexKey)) {
// we ran out of elements to pull
break;
}
// **********************************************************
// The DefaultModelBinder shouldn't always create a new
// instance of elementType in the collection we are updating here.
// If an instance already exists, then we should update it, not create a new one.
// **********************************************************
IList containerModel = bindingContext.Model as IList;
object elementModel = null;
if (containerModel != null && currentIndex < containerModel.Count)
{
elementModel = containerModel[currentIndex];
}
//*****************************************************
ModelBindingContext innerContext = new ModelBindingContext() {
Model = elementModel, // assign the Model property
ModelName = subIndexKey,
ModelState = bindingContext.ModelState,
ModelType = elementType,
PropertyFilter = bindingContext.PropertyFilter,
ValueProvider = bindingContext.ValueProvider
};
object thisElement = elementBinder.BindModel(controllerContext, innerContext);
// we need to merge model errors up
VerifyValueUsability(controllerContext, bindingContext.ModelState, subIndexKey, elementType, thisElement);
modelList.Add(thisElement);
}
// if there weren't any elements at all in the request, just return
if (modelList.Count == 0) {
return null;
}
// replace the original collection
object collection = bindingContext.Model;
CollectionHelpers.ReplaceCollection(elementType, collection, modelList);
return collection;
}
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