C# .NET 4.0 中的只读列表或不可修改列表
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Read-only list or unmodifiable list in .NET 4.0
提问by Chris S
From what I can tell, .NET 4.0 still lacks read-only lists. Why does the framework still lack this functionality? Isn't this one of the commonest pieces of functionality for domain-driven design?
据我所知，.NET 4.0 仍然缺少只读列表。为什么框架仍然缺少这个功能？这不是领域驱动设计最常见的功能之一吗？
One of the few advantages Java has over C# is this in the form of the Collections.unmodifiablelist(list)method, which it seems is long overdue in IList<T> or List<T>.
Java 相对于 C# 的少数优势之一是Collections.unmodifiablelist(list)方法的形式，在 IList<T> 或 List<T> 中似乎早就应该这样做了。
Using IEnumerable<T>is the easiest solution to the question - ToListcan be used and returns a copy.
使用IEnumerable<T>是问题的最简单解决方案 -ToList可以使用并返回副本。
采纳答案by LukeH
You're looking for ReadOnlyCollection, which has been around since .NET2.
您正在寻找ReadOnlyCollection自 .NET2 以来一直存在的 。
IList<string> foo = ...;
// ...
ReadOnlyCollection<string> bar = new ReadOnlyCollection<string>(foo);
or
或者
List<string> foo = ...;
// ...
ReadOnlyCollection<string> bar = foo.AsReadOnly();
This creates a read-only view, which reflects changes made to the wrapped collection.
这将创建一个只读视图，它反映对包装集合所做的更改。
回答by Paul Alexander
In 2.0 you can call AsReadOnlyto get a read-only version of the list. Or wrap an existing IListin a ReadOnlyCollection<T>object.
在 2.0 中，您可以调用AsReadOnly以获取列表的只读版本。或者将一个存在IList的ReadOnlyCollection<T>对象包装在一个对象中。
回答by Jason Watts
How about the ReadOnlyCollectionalready within the framework?
框架中已有的ReadOnlyCollection怎么样？
回答by Ana Betts
If the most common pattern of the list is to iterate through all the elements, IEnumerable<T>or IQueryable<T>can effectively act as a read-only list as well.
如果列表的最常见模式是遍历所有元素，IEnumerable<T>或者IQueryable<T>也可以有效地充当只读列表。
回答by Matthew Dresser
回答by Martin
For those who like to use interfaces:
.NET 4.5 adds the generic IReadOnlyListinterface which is implemented by List<T>for example.
对于那些喜欢使用接口的人：.NET 4.5 增加了IReadOnlyList由List<T>example实现的通用接口。
It is similar to IReadOnlyCollectionand adds an Itemindexer property.
它类似于IReadOnlyCollection并添加了Item索引器属性。
