当从代码中调用web资源时,一个常见的任务是构建一个包含所有必要参数的查询字符串。虽然这绝不是火箭科学,但有一些漂亮的细节需要注意,例如,如果不是第一个参数,则添加&,对参数进行编码等。

实现它的代码非常简单,但有点乏味:

StringBuilder SB = new StringBuilder();
if (NeedsToAddParameter A) 
{ 
  SB.Append("A="); SB.Append(HttpUtility.UrlEncode("TheValueOfA")); 
}

if (NeedsToAddParameter B) 
{
  if (SB.Length>0) SB.Append("&"); 
  SB.Append("B="); SB.Append(HttpUtility.UrlEncode("TheValueOfB")); }
}

这是一个非常常见的任务,人们希望存在一个实用工具类,使其更加优雅和可读。扫描MSDN,我没有找到一个,这让我想到了以下问题:

你所知道的最优雅干净的方法是什么?


当前回答

编辑-正如评论中指出的那样,这不是正确的方法。

有这样一个类——URI类。提供统一资源标识符(URI)的对象表示,并方便访问URI的各个部分。(微软文档)。

下面的例子创建了一个Uri类的实例,并使用它来创建一个WebRequest实例。

c#示例

Uri siteUri = new Uri("http://www.contoso.com/");

WebRequest wr = WebRequest.Create(siteUri);

看一下,这个类上有很多方法。

其他回答

我有一个扩展方法的Uri:

接受匿名对象:uri。WithQuery(new {name = "value"}) 接受字符串/字符串对的集合(例如Dictionary ' 2)。 接受字符串/对象对的集合(例如RouteValueDictionary)。 接受NameValueCollections。 按键对查询值进行排序,以便相同的值产生相同的uri。 每个键支持多个值,保持其原始顺序。


文档版本可以在这里找到。

扩展:

public static Uri WithQuery(this Uri uri, object values)
{
    if (uri == null)
        throw new ArgumentNullException(nameof(uri));

    if (values != null)
    {
        var query = string.Join(
            "&", from p in ParseQueryValues(values)
                 where !string.IsNullOrWhiteSpace(p.Key)
                 let k = HttpUtility.UrlEncode(p.Key.Trim())
                 let v = HttpUtility.UrlEncode(p.Value)
                 orderby k
                 select string.IsNullOrEmpty(v) ? k : $"{k}={v}");

        if (query.Length != 0 || uri.Query.Length != 0)
            uri = new UriBuilder(uri) { Query = query }.Uri;
    }

    return uri;
}

查询解析器:

private static IEnumerable<KeyValuePair<string, string>> ParseQueryValues(object values)
{
    // Check if a name/value collection.
    var nvc = values as NameValueCollection;
    if (nvc != null)
        return from key in nvc.AllKeys
               from val in nvc.GetValues(key)
               select new KeyValuePair<string, string>(key, val);

    // Check if a string/string dictionary.
    var ssd = values as IEnumerable<KeyValuePair<string, string>>;
    if (ssd != null)
        return ssd;

    // Check if a string/object dictionary.
    var sod = values as IEnumerable<KeyValuePair<string, object>>;
    if (sod == null)
    {
        // Check if a non-generic dictionary.
        var ngd = values as IDictionary;
        if (ngd != null)
            sod = ngd.Cast<dynamic>().ToDictionary<dynamic, string, object>(
                p => p.Key.ToString(), p => p.Value as object);

        // Convert object properties to dictionary.
        if (sod == null)
            sod = new RouteValueDictionary(values);
    }

    // Normalize and return the values.
    return from pair in sod
           from val in pair.Value as IEnumerable<string>
            ?? new[] { pair.Value?.ToString() }
           select new KeyValuePair<string, string>(pair.Key, val);
}

下面是测试:

var uri = new Uri("https://stackoverflow.com/yo?oldKey=oldValue");

// Test with a string/string dictionary.
var q = uri.WithQuery(new Dictionary<string, string>
{
    ["k1"] = string.Empty,
    ["k2"] = null,
    ["k3"] = "v3"
});

Debug.Assert(q == new Uri(
    "https://stackoverflow.com/yo?k1&k2&k3=v3"));

// Test with a string/object dictionary.
q = uri.WithQuery(new Dictionary<string, object>
{
    ["k1"] = "v1",
    ["k2"] = new[] { "v2a", "v2b" },
    ["k3"] = null
});

Debug.Assert(q == new Uri(
    "https://stackoverflow.com/yo?k1=v1&k2=v2a&k2=v2b&k3"));

// Test with a name/value collection.
var nvc = new NameValueCollection()
{
    ["k1"] = string.Empty,
    ["k2"] = "v2a"
};

nvc.Add("k2", "v2b");

q = uri.WithQuery(nvc);
Debug.Assert(q == new Uri(
    "https://stackoverflow.com/yo?k1&k2=v2a&k2=v2b"));

// Test with any dictionary.
q = uri.WithQuery(new Dictionary<int, HashSet<string>>
{
    [1] = new HashSet<string> { "v1" },
    [2] = new HashSet<string> { "v2a", "v2b" },
    [3] = null
});

Debug.Assert(q == new Uri(
    "https://stackoverflow.com/yo?1=v1&2=v2a&2=v2b&3"));

// Test with an anonymous object.
q = uri.WithQuery(new
{
    k1 = "v1",
    k2 = new[] { "v2a", "v2b" },
    k3 = new List<string> { "v3" },
    k4 = true,
    k5 = null as Queue<string>
});

Debug.Assert(q == new Uri(
    "https://stackoverflow.com/yo?k1=v1&k2=v2a&k2=v2b&k3=v3&k4=True&k5"));

// Keep existing query using a name/value collection.
nvc = HttpUtility.ParseQueryString(uri.Query);
nvc.Add("newKey", "newValue");

q = uri.WithQuery(nvc);
Debug.Assert(q == new Uri(
    "https://stackoverflow.com/yo?newKey=newValue&oldKey=oldValue"));

// Merge two query objects using the RouteValueDictionary.
var an1 = new { k1 = "v1" };
var an2 = new { k2 = "v2" };

q = uri.WithQuery(
    new RouteValueDictionary(an1).Concat(
        new RouteValueDictionary(an2)));

Debug.Assert(q == new Uri(
    "https://stackoverflow.com/yo?k1=v1&k2=v2"));

下面是一个使用非常基本的语言特性的实现。它是我们必须在Objective C中移植和维护的类的一部分,所以我们选择了更多的代码行,但更容易移植和理解不太熟悉c#的程序员。

        /// <summary>
        /// Builds a complete http url with query strings.
        /// </summary>
        /// <param name="pHostname"></param>
        /// <param name="pPort"></param>
        /// <param name="pPage">ex "/index.html" or index.html</param>
        /// <param name="pGetParams">a Dictionary<string,string> collection containing the key value pairs.  Pass null if there are none.</param>
        /// <returns>a string of the form: http://[pHostname]:[pPort/[pPage]?key1=val1&key2=val2...</returns>

  static public string buildURL(string pHostname, int pPort, string pPage, Dictionary<string,string> pGetParams)
        {
            StringBuilder sb = new StringBuilder(200);
            sb.Append("http://");
            sb.Append(pHostname);
            if( pPort != 80 ) {
                sb.Append(pPort);
            }
            // Allows page param to be passed in with or without leading slash.
            if( !pPage.StartsWith("/") ) {
                sb.Append("/");
            }
            sb.Append(pPage);

            if (pGetParams != null && pGetParams.Count > 0)
            {
                sb.Append("?");
                foreach (KeyValuePair<string, string> kvp in pGetParams)
                {
                    sb.Append(kvp.Key);
                    sb.Append("=");
                    sb.Append( System.Web.HttpUtility.UrlEncode(kvp.Value) );
                    sb.Append("&");
                }
                sb.Remove(sb.Length - 1, 1); // Remove the final '&'
            }
            return sb.ToString();
        }

我使用了DSO提出的解决方案(在8月2日11日7:29回答),他的解决方案不需要使用HttpUtility。然而,根据Dotnetpearls上的一篇文章,使用Dictionary比使用NameValueCollection(在性能上)更快。下面是修改后的DSO解决方案,使用Dictionary代替NameValueCollection。

    public static Dictionary<string, string> QueryParametersDictionary()
    {
        var dictionary = new Dictionary<string, string>();
        dictionary.Add("name", "John Doe");
        dictionary.Add("address.city", "Seattle");
        dictionary.Add("address.state_code", "WA");
        dictionary.Add("api_key", "5352345263456345635");

        return dictionary;
    }

    public static string ToQueryString(Dictionary<string, string> nvc)
    {
        StringBuilder sb = new StringBuilder();

        bool first = true;

        foreach (KeyValuePair<string, string> pair in nvc)
        {
                if (!first)
                {
                    sb.Append("&");
                }

                sb.AppendFormat("{0}={1}", Uri.EscapeDataString(pair.Key), Uri.EscapeDataString(pair.Value));

                first = false;
        }

        return sb.ToString();
    }

我刚才回答了一个类似的问题。基本上,最好的方法是使用HttpValueCollection类。净的请求。QueryString属性实际上是,不幸的是,它是。net框架内部的。 您可以使用Reflector来抓取它(并将其放入您的Utils类中)。通过这种方式,您可以像操作NameValueCollection一样操作查询字符串,但是需要考虑所有url编码/解码问题。

HttpValueCollection扩展了NameValueCollection,并有一个接受编码查询字符串(包括&和问号)的构造函数,它覆盖了ToString()方法,以便稍后从底层集合重新构建查询字符串。

例子:

  var coll = new HttpValueCollection();

  coll["userId"] = "50";
  coll["paramA"] = "A";
  coll["paramB"] = "B";      

  string query = coll.ToString(true); // true means use urlencode

  Console.WriteLine(query); // prints: userId=50&paramA=A&paramB=B

Flurl[披露:我是作者]支持通过匿名对象(以及其他方式)构建查询字符串:

var url = "http://www.some-api.com".SetQueryParams(new
{
    api_key = ConfigurationManager.AppSettings["SomeApiKey"],
    max_results = 20,
    q = "Don't worry, I'll get encoded!"
});

可选的Flurl。Http companion lib允许您在相同的流畅调用链上执行Http调用,将其扩展为一个成熟的REST客户端:

T result = await "https://api.mysite.com"
    .AppendPathSegment("person")
    .SetQueryParams(new { ap_key = "my-key" })
    .WithOAuthBearerToken("MyToken")
    .PostJsonAsync(new { first_name = firstName, last_name = lastName })
    .ReceiveJson<T>();

完整的软件包在NuGet上可用:

PM>安装包Flurl。Http

或者只是独立的URL构建器:

PM>安装包Flurl