c# - 如何检查我的未初始化变量是否为 List 类型？

Question

我有以下类定义:

[ActionsClass[typeof(MyActions)]
public class NkProject
    {
        int ProjectId;
        IList<NkItem> Items;
        NkItem SingleItem;
    }

这个类主要只包含字段，类属性说明哪个类负责“处理”这个类作为更大框架的一部分。

我使用反射解析此文件以生成一些元数据，我想知道“Items”是否属于列表类型(或充当列表的任何类型的集合)，但到目前为止我已经尝试过的所有内容失败。我正在遍历一组 FieldInfo[] 对象。

1. 检查 IEnumerable:

   
   if(field.FieldType.GetInterface("IEnumerable") != null)
   

   This also detects strings as IEnumerables, which is incorrect. I'd prefer if strings fail to pass this check and get treated as primitives in a sense (the else of the above if).

2. Changed above to: if(field is ICollection) and that also fails.

3. Changed above to: if(field is IList && field.GetType().IsGenericType) and it still fails to be detected correctly.

Is there a way to look only at the type of the variable references to ascertain whether Items is of type List and a parallel check for string Items fails? I'm guessing #2 and #3 above fail because Items is not an object and thus there isn't any inheritance information attached to it. I could be wrong, but I think that's what is happening. A field.GetType().Name returns the type as IList`1. Not sure how to get around this.

EDIT/UPDATE: If the above check fails, and a string goes through, the output meta is incorrectly formatted. Since, if it's a collection/list of items, I need to fetch further metadata for them (via the appropriately set attributes). This step is only executed if the variable is of type List/Collection but not if it's a single reference or a primitive.

Reflection code:

foreach (var field in fieldInfo)
{
    Property property;

    //If it's a collection field, get the appropriate collection name as set in its attribute
    if (field.FieldType.GetInterface("IEnumerable") != null) //currently lets strings pass through too.
    {
        //Get the type of the "type argument" of the IEnumerable
        Type[] typeArgs = field.FieldType.GetGenericArguments();
        //Get the collection name for that type to use in the XML
        MyAttribute att = (MyAttribute )Attribute.GetCustomAttribute(typeArgs[0], typeof(MyAttribute ));

        if (att == null)
            throw new ArgumentException("Using collection: {0} in Your class: {1}. Collection must have MyAttribute[Collection=\"\"] attribute defined on its class declaration.");

        else
        {   
         //do something with meta data          
        }
    }

    //If non-collection, possibly primitive field do something else
    else
    {
        //do other stuff here.
    }
}

Answer 1

您可以使用泛型类型信息来检查它是否是一个列表

if(field.FieldType.IsGenericType 
    && field.FieldType.GetGenericTypeDefinition() == typeof(List<>))

目前我的代码库中有以下针对此类情况的函数。

public static bool Closes(this Type type, Type openType)
{
    if (type == null)
        return false;

    if (type.IsGenericType && type.GetGenericTypeDefinition() == openType) return true;

    foreach (var @interface in type.GetInterfaces())
    {
        if (@interface.Closes(openType)) return true;
    }

    return type.BaseType.Closes(openType);
}

这样你就可以调用

field.FieldType.Closes(typeof(List<>)