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
虽然不够优雅，但我选择了一个更简单的版本，它不使用NameValueCollecitons——只是一个包装在StringBuilder周围的构建器模式。
public class UrlBuilder
{
#region Variables / Properties
private readonly StringBuilder _builder;
#endregion Variables / Properties
#region Constructor
public UrlBuilder(string urlBase)
{
_builder = new StringBuilder(urlBase);
}
#endregion Constructor
#region Methods
public UrlBuilder AppendParameter(string paramName, string value)
{
if (_builder.ToString().Contains("?"))
_builder.Append("&");
else
_builder.Append("?");
_builder.Append(HttpUtility.UrlEncode(paramName));
_builder.Append("=");
_builder.Append(HttpUtility.UrlEncode(value));
return this;
}
public override string ToString()
{
return _builder.ToString();
}
#endregion Methods
}
根据现有的答案，我确保使用HttpUtility。UrlEncode调用。它是这样使用的:
string url = new UrlBuilder("http://www.somedomain.com/")
.AppendParameter("a", "true")
.AppendParameter("b", "muffin")
.AppendParameter("c", "muffin button")
.ToString();
// Result: http://www.somedomain.com?a=true&b=muffin&c=muffin%20button
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();
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"));
我需要为我正在开发的可移植类库(PCL)解决同样的问题。在这种情况下，我没有访问系统的权限。所以我不能用ParseQueryString。
相反，我使用System.Net.Http.FormUrlEncodedContent像这样:
var url = new UriBuilder("http://example.com");
url.Query = new FormUrlEncodedContent(new Dictionary<string,string>()
{
{"param1", "val1"},
{"param2", "val2"},
{"param3", "val3"},
}).ReadAsStringAsync().Result;
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
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¶mA=A¶mB=B
