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
适用于NameValueCollection中每个键的多个值。
例:{{“k1”、“v1”},{“k1”、“v1”}}= > ? k1 = v1&k1 = v1
/// <summary>
/// Get query string for name value collection.
/// </summary>
public static string ToQueryString(this NameValueCollection collection,
bool prefixQuestionMark = true)
{
collection.NullArgumentCheck();
if (collection.Keys.Count == 0)
{
return "";
}
var buffer = new StringBuilder();
if (prefixQuestionMark)
{
buffer.Append("?");
}
var append = false;
for (int i = 0; i < collection.Keys.Count; i++)
{
var key = collection.Keys[i];
var values = collection.GetValues(key);
key.NullCheck();
values.NullCheck();
foreach (var value in values)
{
if (append)
{
buffer.Append("&");
}
append = true;
buffer.AppendFormat("{0}={1}", key.UrlEncode(), value.UrlEncode());
}
}
return buffer.ToString();
}
其他回答
未经测试，但我认为沿着这些路线的东西会工作得很好
public class QueryString
{
private Dictionary<string,string> _Params = new Dictionary<string,string>();
public overide ToString()
{
List<string> returnParams = new List<string>();
foreach (KeyValuePair param in _Params)
{
returnParams.Add(String.Format("{0}={1}", param.Key, param.Value));
}
// return String.Format("?{0}", String.Join("&", returnParams.ToArray()));
// credit annakata
return "?" + String.Join("&", returnParams.ToArray());
}
public void Add(string key, string value)
{
_Params.Add(key, HttpUtility.UrlEncode(value));
}
}
QueryString query = new QueryString();
query.Add("param1", "value1");
query.Add("param2", "value2");
return query.ToString();
另一种方法是创建一个类NameValueCollection的扩展，返回完整的Url:
public static class CustomMethods
{
public static string ToUrl(this System.Collections.Specialized.NameValueCollection collection)
{
if (collection.Count == 0) return "";
string completeUrl = "?";
for (int i = 0; i < collection.Count; i++)
{
completeUrl += new Page().Server.UrlEncode(collection.GetKey(i)) + "=" + new Page().Server.UrlEncode(collection.Get(i));
if ((i + 1) < collection.Count) completeUrl += "&";
}
return completeUrl;
}
}
然后，你可以使用你的新方法，例如:
System.Collections.Specialized.NameValueCollection qString = new System.Collections.Specialized.NameValueCollection();
qString.Add("name", "MyName");
qString.Add("email", "myemail@test.com");
qString.ToUrl(); //Result: "?name=MyName&email=myemail%40test.com"
从Roy Tinker的评论中得到灵感，我最终在Uri类上使用了一个简单的扩展方法，使我的代码简洁干净:
using System.Web;
public static class HttpExtensions
{
public static Uri AddQuery(this Uri uri, string name, string value)
{
var httpValueCollection = HttpUtility.ParseQueryString(uri.Query);
httpValueCollection.Remove(name);
httpValueCollection.Add(name, value);
var ub = new UriBuilder(uri);
ub.Query = httpValueCollection.ToString();
return ub.Uri;
}
}
用法:
Uri url = new Uri("http://localhost/rest/something/browse").
AddQuery("page", "0").
AddQuery("pageSize", "200");
编辑-标准兼容的变体
正如一些人指出的那样，httpValueCollection.ToString()以一种不符合标准的方式编码Unicode字符。这是通过调用HttpUtility来处理此类字符的相同扩展方法的变体。UrlEncode方法代替已弃用的HttpUtility方法。UrlEncodeUnicode方法。
using System.Web;
public static Uri AddQuery(this Uri uri, string name, string value)
{
var httpValueCollection = HttpUtility.ParseQueryString(uri.Query);
httpValueCollection.Remove(name);
httpValueCollection.Add(name, value);
var ub = new UriBuilder(uri);
// this code block is taken from httpValueCollection.ToString() method
// and modified so it encodes strings with HttpUtility.UrlEncode
if (httpValueCollection.Count == 0)
ub.Query = String.Empty;
else
{
var sb = new StringBuilder();
for (int i = 0; i < httpValueCollection.Count; i++)
{
string text = httpValueCollection.GetKey(i);
{
text = HttpUtility.UrlEncode(text);
string val = (text != null) ? (text + "=") : string.Empty;
string[] vals = httpValueCollection.GetValues(i);
if (sb.Length > 0)
sb.Append('&');
if (vals == null || vals.Length == 0)
sb.Append(val);
else
{
if (vals.Length == 1)
{
sb.Append(val);
sb.Append(HttpUtility.UrlEncode(vals[0]));
}
else
{
for (int j = 0; j < vals.Length; j++)
{
if (j > 0)
sb.Append('&');
sb.Append(val);
sb.Append(HttpUtility.UrlEncode(vals[j]));
}
}
}
}
}
ub.Query = sb.ToString();
}
return ub.Uri;
}
只针对那些需要VB的人。NET版本的顶级答案:
Public Function ToQueryString(nvc As System.Collections.Specialized.NameValueCollection) As String
Dim array As String() = nvc.AllKeys.SelectMany(Function(key As String) nvc.GetValues(key), Function(key As String, value As String) String.Format("{0}={1}", System.Web.HttpUtility.UrlEncode(key), System.Web.HttpUtility.UrlEncode(value))).ToArray()
Return "?" + String.Join("&", array)
End Function
以及没有LINQ的版本:
Public Function ToQueryString(nvc As System.Collections.Specialized.NameValueCollection) As String
Dim lsParams As New List(Of String)()
For Each strKey As String In nvc.AllKeys
Dim astrValue As String() = nvc.GetValues(strKey)
For Each strValue As String In astrValue
lsParams.Add(String.Format("{0}={1}", System.Web.HttpUtility.UrlEncode(strKey), System.Web.HttpUtility.UrlEncode(strValue)))
Next ' Next strValue
Next ' strKey
Dim astrParams As String() = lsParams.ToArray()
lsParams.Clear()
lsParams = Nothing
Return "?" + String.Join("&", astrParams)
End Function ' ToQueryString
和没有LINQ的c#版本:
public static string ToQueryString(System.Collections.Specialized.NameValueCollection nvc)
{
List<string> lsParams = new List<string>();
foreach (string strKey in nvc.AllKeys)
{
string[] astrValue = nvc.GetValues(strKey);
foreach (string strValue in astrValue)
{
lsParams.Add(string.Format("{0}={1}", System.Web.HttpUtility.UrlEncode(strKey), System.Web.HttpUtility.UrlEncode(strValue)));
} // Next strValue
} // Next strKey
string[] astrParams =lsParams.ToArray();
lsParams.Clear();
lsParams = null;
return "?" + string.Join("&", astrParams);
} // End Function ToQueryString
如果你仔细观察，QueryString属性是一个NameValueCollection。当我做了类似的事情，我通常对序列化和反序列化感兴趣，所以我的建议是建立一个NameValueCollection，然后传递给:
using System.Linq;
using System.Web;
using System.Collections.Specialized;
private string ToQueryString(NameValueCollection nvc)
{
var array = (
from key in nvc.AllKeys
from value in nvc.GetValues(key)
select string.Format(
"{0}={1}",
HttpUtility.UrlEncode(key),
HttpUtility.UrlEncode(value))
).ToArray();
return "?" + string.Join("&", array);
}
我想在LINQ中也有一种非常优雅的方式来做到这一点……
