Question

我有WebClient这样：

WebClient _webClient = new WebClient
{
    UseDefaultCredentials = true,
    Encoding = System.Text.Encoding.UTF8,               
};
_webClient.Headers.Add("user-agent", "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.2; .NET CLR 1.0.3705;)");

我想使用对象初始值设定项初始化Headers：

WebClient _webClient = new WebClient
{
    UseDefaultCredentials = true,
    Encoding = System.Text.Encoding.UTF8,
    Headers = new WebHeaderCollection
    {
        "user-agent",
        "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.2; .NET CLR 1.0.3705;)",
    }
};

但我不知道怎么写。有可能吗？

更新2016/07/07

大概是indexer和Object and Collection Initializers。在正常的集合中，例如List<int> numbers 您可以通过以下代码

来初始化

    List<int> numers = new List<int> {
        1, 2, 3
    };

但WebHeaderCollectio我们想要启动的名称标题List<...>只是WebClient中的通用属性

public class WebClient : Component
{
    ...
    public WebHeaderCollection Headers { get; set; }
    ...
}

Object and Collection Initializers提到集合初始值设定项允许您在初始化实现IEnumerable的集合类或使用Add扩展方法的类时指定一个或多个元素初始值设定项。

因此，我们检查WebHeaderCollection类

public class WebHeaderCollection : NameValueCollection, ISerializable
{
    public string this[HttpResponseHeader header] { get; set; }

    public string this[HttpRequestHeader header] { get; set; }

    public void Add(string header);

    public void Add(HttpRequestHeader header, string value);

    public void Add(HttpResponseHeader header, string value);
}

WebHeaderCollection : NameValueCollection : NameObjectCollectionBase : IEnumerable

最后有一个我的练习样本

 class Program
    {
        static void Main(string[] args)
        {
            PeopleEnumerable peopleEnumerable = new PeopleEnumerable {
                { "Michael", "1" },
                { "Mike", "2" },
                { "Butters;3" },
            };

            Console.WriteLine(peopleEnumerable["1"]);
            Console.WriteLine(peopleEnumerable["2"]);
            Console.WriteLine(peopleEnumerable["3"]);
        }
    }

    public class PeopleEnumerable : IEnumerable
    {
        Dictionary<string, string> _peopels = new Dictionary<string, string>();

        public string this[string id]
        {
            get
            {
                return _peopels[id];
            }
            set
            {
                _peopels[id] = value;
            }
        }

        public void Add(string name, string id)
        {
            _peopels.Add(id, name);
        }
        public void Add(string nameAndId)
        {
            var name = nameAndId.Split(';')[0];
            var id = nameAndId.Split(';')[1];

            _peopels.Add(id, name);
        }

        public IEnumerator GetEnumerator()
        {
            throw new NotImplementedException();
        }
    }

您需要实现IEnumerable，否则您将获得无法使用集合初始值设定项初始化类型'PeopleEnumerable'，因为它没有实现'System.Collections.IEnumerable'

Answer 1

你可以这样做。您必须用冒号（:）分割属性及其值：

WebClient _webClient = new WebClient
    {
        UseDefaultCredentials = true,
        Encoding = System.Text.Encoding.UTF8,
        Headers = new WebHeaderCollection
        {
            "user-agent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.2; .NET CLR 1.0.3705;)"
        }
    };

Answer 2

我认为您也可以这样做（标题中没有:）：

private static WebClient _doClient = new WebClient
{
    BaseAddress = "https://api.digitalocean.com/v2/domains/example.com/",
    Headers = new WebHeaderCollection { { "Authorization", "Bearer " + _digitalOceanApiKey } }
};

如何使用对象初始化器初始化WebClient？

2 个答案: