我如何知道某个属性是否是通用集合

Question

我需要使用 PropertyInfo 类了解类中属性的类型是否是通用集合（List、ObservableCollection）。

foreach (PropertyInfo p in (o.GetType()).GetProperties())
{
    if(p is Collection<T> ????? )

}

Answer 1

Type tColl = typeof(ICollection<>);
foreach (PropertyInfo p in (o.GetType()).GetProperties()) {
    Type t = p.PropertyType;
    if (t.IsGenericType && tColl.IsAssignableFrom(t.GetGenericTypeDefinition()) ||
        t.GetInterfaces().Any(x => x.IsGenericType && x.GetGenericTypeDefinition() == tColl)) {
        Console.WriteLine(p.Name + " IS an ICollection<>");
    } else {
        Console.WriteLine(p.Name + " is NOT an ICollection<>");
    }
}

您需要测试 t.IsGenericType 和 x.IsGenericType，否则如果类型不是泛型，GetGenericTypeDefinition() 将引发异常。

如果属性声明为 ICollection，则 tColl.IsAssignableFrom(t.GetGenericTypeDefinition()) 将返回 true。

如果该属性被声明为实现 ICollection 的类型，则
t.GetInterfaces().Any(x => x.IsGenericType && x.GetGenericTypeDefinition() == tColl) 将返回 true。

请注意，例如，对于 List，tColl.IsAssignableFrom(t.GetGenericTypeDefinition()) 返回 false。

---

我已经测试了所有这些组合的 MyT o = new MyT();

private interface IMyCollInterface1 : ICollection<int> { }
private interface IMyCollInterface2<T> : ICollection<T> { }
private class MyCollType1 : IMyCollInterface1 { ... }
private class MyCollType2 : IMyCollInterface2<int> { ... }
private class MyCollType3<T> : IMyCollInterface2<T> { ... }

private class MyT
{
    public ICollection<int> IntCollection { get; set; }
    public List<int> IntList { get; set; }
    public IMyCollInterface1 iColl1 { get; set; }
    public IMyCollInterface2<int> iColl2 { get; set; }
    public MyCollType1 Coll1 { get; set; }
    public MyCollType2 Coll2 { get; set; }
    public MyCollType3<int> Coll3 { get; set; }
    public string StringProp { get; set; }
}

输出：

IntCollection IS an ICollection<>
IntList IS an ICollection<>
iColl1 IS an ICollection<>
iColl2 IS an ICollection<>
Coll1 IS an ICollection<>
Coll2 IS an ICollection<>
Coll3 IS an ICollection<>
StringProp is NOT an ICollection<>

Answer 2

GetGenericTypeDefinition 和 typeof(Collection<>) 将完成这项工作：

if(p.PropertyType.IsGenericType && typeof(Collection<>).IsAssignableFrom(p.PropertyType.GetGenericTypeDefinition())