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
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();
}
其他回答
只是想说说我的看法
public static class HttpClientExt
{
public static Uri AddQueryParams(this Uri uri, string query)
{
var ub = new UriBuilder(uri);
ub.Query = string.IsNullOrEmpty(uri.Query) ? query : string.Join("&", uri.Query.Substring(1), query);
return ub.Uri;
}
public static Uri AddQueryParams(this Uri uri, IEnumerable<string> query)
{
return uri.AddQueryParams(string.Join("&", query));
}
public static Uri AddQueryParams(this Uri uri, string key, string value)
{
return uri.AddQueryParams(string.Join("=", HttpUtility.UrlEncode(key), HttpUtility.UrlEncode(value)));
}
public static Uri AddQueryParams(this Uri uri, params KeyValuePair<string,string>[] kvps)
{
return uri.AddQueryParams(kvps.Select(kvp => string.Join("=", HttpUtility.UrlEncode(kvp.Key), HttpUtility.UrlEncode(kvp.Value))));
}
public static Uri AddQueryParams(this Uri uri, IDictionary<string, string> kvps)
{
return uri.AddQueryParams(kvps.Select(kvp => string.Join("=", HttpUtility.UrlEncode(kvp.Key), HttpUtility.UrlEncode(kvp.Value))));
}
public static Uri AddQueryParams(this Uri uri, NameValueCollection nvc)
{
return uri.AddQueryParams(nvc.AllKeys.SelectMany(nvc.GetValues, (key, value) => string.Join("=", HttpUtility.UrlEncode(key), HttpUtility.UrlEncode(value))));
}
}
文档说uri。查询将以?如果它是非空的，如果你要修改它，你应该把它剪掉。
注意HttpUtility。UrlEncode可以在System.Web中找到。
用法:
var uri = new Uri("https://api.del.icio.us/v1/posts/suggest").AddQueryParam("url","http://stackoverflow.com")
public string UrlQueryStr(object data)
{
if (data == null)
return string.Empty;
object val;
StringBuilder sb = new StringBuilder();
foreach (PropertyDescriptor prop in TypeDescriptor.GetProperties(data))
{
if ((val = prop.GetValue(data)) != null)
{
sb.AppendFormat("{0}{1}={2}", sb.Length == 0 ? '?' : '&',
HttpUtility.UrlEncode(prop.Name), HttpUtility.UrlEncode(val.ToString()));
}
}
return sb.ToString();
}
public static string ToQueryString(this Dictionary<string, string> source)
{
return String.Join("&", source.Select(kvp => String.Format("{0}={1}", HttpUtility.UrlEncode(kvp.Key), HttpUtility.UrlEncode(kvp.Value))).ToArray());
}
public static string ToQueryString(this NameValueCollection source)
{
return String.Join("&", source.Cast<string>().Select(key => String.Format("{0}={1}", HttpUtility.UrlEncode(key), HttpUtility.UrlEncode(source[key]))).ToArray());
}
HttpValueCollection的可链接包装类:
namespace System.Web.Mvc {
public class QueryStringBuilder {
private NameValueCollection collection;
public QueryStringBuilder() {
collection = System.Web.HttpUtility.ParseQueryString(string.Empty);
}
public QueryStringBuilder Add(string key, string value) {
collection.Add(key, value);
return this;
}
public QueryStringBuilder Remove(string key) {
collection.Remove(key);
return this;
}
public string this[string key] {
get { return collection[key]; }
set { collection[key] = value; }
}
public string ToString() {
return collection.ToString();
}
}
}
使用示例:
QueryStringBuilder parameters = new QueryStringBuilder()
.Add("view", ViewBag.PageView)
.Add("page", ViewBag.PageNumber)
.Add("size", ViewBag.PageSize);
string queryString = parameters.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();
}
