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
下面的代码是从ToString的HttpValueCollection实现中截取的，通过ILSpy，它会给你一个name=value querystring。
不幸的是，HttpValueCollection是一个内部类，只有当你使用HttpUtility.ParseQueryString()时才会返回。我删除了它的所有视图状态部分，它默认编码:
public static class HttpExtensions
{
public static string ToQueryString(this NameValueCollection collection)
{
// This is based off the NameValueCollection.ToString() implementation
int count = collection.Count;
if (count == 0)
return string.Empty;
StringBuilder stringBuilder = new StringBuilder();
for (int i = 0; i < count; i++)
{
string text = collection.GetKey(i);
text = HttpUtility.UrlEncodeUnicode(text);
string value = (text != null) ? (text + "=") : string.Empty;
string[] values = collection.GetValues(i);
if (stringBuilder.Length > 0)
{
stringBuilder.Append('&');
}
if (values == null || values.Length == 0)
{
stringBuilder.Append(value);
}
else
{
if (values.Length == 1)
{
stringBuilder.Append(value);
string text2 = values[0];
text2 = HttpUtility.UrlEncodeUnicode(text2);
stringBuilder.Append(text2);
}
else
{
for (int j = 0; j < values.Length; j++)
{
if (j > 0)
{
stringBuilder.Append('&');
}
stringBuilder.Append(value);
string text2 = values[j];
text2 = HttpUtility.UrlEncodeUnicode(text2);
stringBuilder.Append(text2);
}
}
}
}
return stringBuilder.ToString();
}
}
其他回答
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);
与已接受的解决方案相同，但转换为“点”LINQ语法…
private string ToQueryString(NameValueCollection nvc)
{
if (nvc == null) return String.Empty;
var queryParams =
string.Join("&", nvc.AllKeys.Select(key =>
string.Join("&", nvc.GetValues(key).Select(v => string.Format("{0}={1}", HttpUtility.UrlEncode(key), HttpUtility.UrlEncode(v))))));
return "?" + queryParams;
}
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
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());
}
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);
}
