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

基于扩展方法的快速版本:

class Program
{
    static void Main(string[] args)
    {
        var parameters = new List<KeyValuePair<string, string>>
                             {
                                 new KeyValuePair<string, string>("A", "AValue"),
                                 new KeyValuePair<string, string>("B", "BValue")
                             };

        string output = "?" + string.Join("&", parameters.ConvertAll(param => param.ToQueryString()).ToArray());
    }
}

public static class KeyValueExtensions
{
    public static string ToQueryString(this KeyValuePair<string, string> obj)
    {
        return obj.Key + "=" + HttpUtility.UrlEncode(obj.Value);
    }
}

可以使用where子句来选择将哪些参数添加到字符串中。

其他回答

这里有一种流畅的/lambda-ish方式作为扩展方法(结合了前面文章中的概念),它支持对同一个键使用多个值。我个人更喜欢扩展,而不是包装,以便其他团队成员能够发现这类内容。请注意,关于编码方法存在争议,Stack Overflow(其中一篇)和MSDN博客上有很多关于它的帖子(比如这篇)。

public static string ToQueryString(this NameValueCollection source)
{
    return String.Join("&", source.AllKeys
        .SelectMany(key => source.GetValues(key)
            .Select(value => String.Format("{0}={1}", HttpUtility.UrlEncode(key), HttpUtility.UrlEncode(value))))
        .ToArray());
}

Edit: null支持,不过您可能需要根据您的特定情况对其进行调整

public static string ToQueryString(this NameValueCollection source, bool removeEmptyEntries)
{
    return source != null ? String.Join("&", source.AllKeys
        .Where(key => !removeEmptyEntries || source.GetValues(key)
            .Where(value => !String.IsNullOrEmpty(value))
            .Any())
        .SelectMany(key => source.GetValues(key)
            .Where(value => !removeEmptyEntries || !String.IsNullOrEmpty(value))
            .Select(value => String.Format("{0}={1}", HttpUtility.UrlEncode(key), value != null ? HttpUtility.UrlEncode(value) : string.Empty)))
        .ToArray())
        : string.Empty;
}

我将以下方法添加到PageBase类中。

protected void Redirect(string url)
    {
        Response.Redirect(url);
    }
protected void Redirect(string url, NameValueCollection querystrings)
    {
        StringBuilder redirectUrl = new StringBuilder(url);

        if (querystrings != null)
        {
            for (int index = 0; index < querystrings.Count; index++)
            {
                if (index == 0)
                {
                    redirectUrl.Append("?");
                }

                redirectUrl.Append(querystrings.Keys[index]);
                redirectUrl.Append("=");
                redirectUrl.Append(HttpUtility.UrlEncode(querystrings[index]));

                if (index < querystrings.Count - 1)
                {
                    redirectUrl.Append("&");
                }
            }
        }

        this.Redirect(redirectUrl.ToString());
    }

电话:

NameValueCollection querystrings = new NameValueCollection();    
querystrings.Add("language", "en");
querystrings.Add("id", "134");
this.Redirect("http://www.mypage.com", querystrings);

查询字符串可以通过以下方式添加到URL:

创建名称值集合对象 将查询字符串项及其值添加到此对象 将此名称值集合对象编码为下面链接中提供的代码的url

https://blog.codingnovice.com/blog

public ActionResult Create()
{
    //declaring name value collection object
    NameValueCollection collection = new NameValueCollection();

    //adding new value to the name value collection object
    collection.Add("Id1", "wwe323");
    collection.Add("Id2", "454w");
    collection.Add("Id3", "tyt5656");
    collection.Add("Id4", "343wdsd");

    //generating query string
    string url = GenerateQueryString(collection);

    return View();
}

private string GenerateQueryString(NameValueCollection collection)
{
    var querystring = (
        from key in collection.AllKeys
        from value in collection.GetValues(key)
        select string.Format("{0}={1}",
            HttpUtility.UrlEncode(key),
            HttpUtility.UrlEncode(value))
    ).ToArray();
    return "?" + string.Join("&", querystring);
}
// USAGE
[TestMethod]
public void TestUrlBuilder()
{
    Console.WriteLine(
        new UrlBuilder("http://www.google.com?A=B")
            .AddPath("SomePathName")
            .AddPath("AnotherPathName")
            .SetQuery("SomeQueryKey", "SomeQueryValue")
            .AlterQuery("A", x => x + "C"));
}

输出:

http://www.google.com/SomePathName/AnotherPathName?A=BC&SomeQueryKey=SomeQueryValue

的代码;你们都可以在某个地方,以某种方式感谢我

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;

// By Demetris Leptos
namespace TheOperator.Foundation.Web
{
    public class UrlBuilder
    {
        public string Scheme { get; set; }

        public string Host { get; set; }

        public int? Port { get; set; }

        public List<string> Paths { get; set; }

        public SortedDictionary<string, string> QueryPairs { get; set; }

        public UrlBuilder(string url)
        {
            this.Paths = new List<string>();
            this.QueryPairs = new SortedDictionary<string, string>();

            string path = null;
            string query = null;
            Uri relativeUri = null;
            if (!Uri.TryCreate(url, UriKind.Relative, out relativeUri))
            {
                var uriBuilder = new UriBuilder(url);
                this.Scheme = uriBuilder.Scheme;
                this.Host = uriBuilder.Host;
                this.Port = uriBuilder.Port;
                path = uriBuilder.Path;
                query = uriBuilder.Query;
            }
            else
            {
                var queryIndex = url.IndexOf('?');
                if (queryIndex >= 0)
                {
                    path = url.Substring(0, queryIndex);
                    query = url.Substring(queryIndex + 1);
                }
                else
                {
                    path = url;
                }
            }
            this.Paths.AddRange(path.Split(new char[] { '/' }, StringSplitOptions.RemoveEmptyEntries));
            if (query != null)
            {
                var queryKeyValuePairs = HttpUtility.ParseQueryString(query);
                foreach (var queryKey in queryKeyValuePairs.AllKeys)
                {
                    this.QueryPairs[queryKey] = queryKeyValuePairs[queryKey];
                }
            }
        }

        public UrlBuilder AddPath(string value)
        {
            this.Paths.Add(value);
            return this;
        }

        public UrlBuilder SetQuery(string key, string value)
        {
            this.QueryPairs[key] = value;
            return this;
        }

        public UrlBuilder RemoveQuery(string key)
        {
            this.QueryPairs.Remove(key);
            return this;
        }

        public UrlBuilder AlterQuery(string key, Func<string, string> alterMethod, bool removeOnNull = false)
        {
            string value;
            this.QueryPairs.TryGetValue(key, out value);
            value = alterMethod(value);
            if (removeOnNull && value == null)
            {
                return this.RemoveQuery(key);
            }
            else
            {
                return this.SetQuery(key, value);
            }
        }

        public override string ToString()
        {
            var path = !string.IsNullOrWhiteSpace(this.Host)
                ? string.Join("/", this.Host, string.Join("/", this.Paths))
                : string.Join("/", this.Paths);
            var query = string.Join("&", this.QueryPairs.Select(x => string.Concat(x.Key, "=", HttpUtility.UrlEncode(x.Value))));
            return string.Concat(
                !string.IsNullOrWhiteSpace(this.Scheme) ? string.Concat(this.Scheme, "://") : null,
                path,
                !string.IsNullOrWhiteSpace(query) ? string.Concat("?", query) : null);
        }
    }
}

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();
        }