c# - "this[0]"在 C# 中是什么意思？

Question

我在浏览一些库代码时看到了如下方法:

public CollapsingRecordNodeItemList List
{
    get { return this[0] as CollapsingRecordNodeItemList; }
}

包含此方法的类不是列表或可迭代的东西，那么 this[0] 到底是什么意思？

Answer 1

寻找 indexer在类里面。

C# 允许您定义索引器以允许此类访问。

这是“SampleCollection”官方指南中的示例。

public T this[int i]
    {
        get
        {
            // This indexer is very simple, and just returns or sets 
            // the corresponding element from the internal array. 
            return arr[i];
        }
        set
        {
            arr[i] = value;
        }
    }

这是来自 the official language specification 的定义:

An indexer is a member that enables objects to be indexed in the same way as an array. An indexer is declared like a property except that the name of the member is this followed by a parameter list written between the delimiters [ and ]. The parameters are available in the accessor(s) of the indexer. Similar to properties, indexers can be read-write, read-only, and write-only, and the accessor(s) of an indexer can be virtual.

可以在规范的 10.9 索引器 部分找到完整的定义。