Question

我想检查一个值是否是任何类型的ObservableCollection类型，或者不是在C＃中？

例如：我可以检查值是否为字符串类型，如下所示：

string value = "value to Check";
bool b = value.GetType().Equals(typeof(string));  // b =true

但是如果我需要检查某个值是否为ObservableCollection，无论组成类型如何，我该怎么做？

例如：

ObservableCollection<T> collection = new ObservableCollection<T>();

如果我这样检查

bool b = collection.GetType().Equals(typeof(ObservableCollection<>)); // b=false

如何检查值是否为集合？

Answer 1

尝试

bool b = collection.GetType().IsGenericType &&
           collection.GetType().GetGenericTypeDefinition() == typeof(ObservableCollection<>);

Answer 2

您可以这样检查：

public static bool IsObservableCollection(object candidate) {
    if (null == candidate) return false;

    var theType = candidate.GetType();
    bool itIs = theType.IsGenericType() && 
        !theType.IsGenericTypeDefinition()) &&
        (theType.GetGenericTypeDefinition() == typeof(ObservableCollection<>));

    return itIs;
}

您还可以获取元素类型：

public static Type GetObservableCollectionElement(object candidate) {
    bool isObservableCollection = IsObservableCollection(candidate);
    if (!isObservableCollection) return null;

    var elementType = candidate.GetType().GetGenericArguments()[0];
    return elementType;
}

修改

实际上以动态方式使用ObservableCollection有点棘手。如果你看一下ObservableCollection<T>类：

ObservableCollection<T> : Collection<T>, INotifyCollectionChanged, INotifyPropertyChanged

你会注意到它扩展了Collection<T>并且它实现了2个接口。

因此，由于每个Collection<T>也是非泛型IEnumerable，您可以推断动态已知的ObservableCollection，如下所示：

object someObject = ... bool itsAnObservableCollection = IsObservableCollection(someObject); if (itsAnObservableCollection) { IEnumerable elements = someObject as IEnumerable; // and try to reason about the elements in this manner foreach (var element in elements) { ... } INotifyCollectionChanged asCC = someObject as INotifyCollectionChanged; INotifyPropertyChanged asPC = someObject as INotifyPropertyChanged; // and try to let yourself receive notifications in this manner asCC.CollectionChanged += (sender, e) => { var newItems = e.NewItems; var oldItems = e.OldItems; ... }; asPC.PropertyChanged += (sender, e) => { var propertyName = e.PropertyName; ... }; }

Answer 3

根据您的需要，您还可以检查它是否实现了INotifyCollectionChanged。

if (someCollection is INotifyCollectionChanged observable)
    observable.CollectionChanged += CollectionChanged;

Answer 4

集合的类型是通用的，您要测试类型的通用定义：

collection.GetType()
  .GetGenericTypeDefinition()
  .Equals(typeof(ObservableCollection<>))

检查对象是否是ObservableCollection？

4 个答案: