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?
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();
}
}
我的提供:
public static Uri AddQuery(this Uri uri, string name, string value)
{
// this actually returns HttpValueCollection : NameValueCollection
// which uses unicode compliant encoding on ToString()
var query = HttpUtility.ParseQueryString(uri.Query);
query.Add(name, value);
var uriBuilder = new UriBuilder(uri)
{
Query = query.ToString()
};
return uriBuilder.Uri;
}
用法:
var uri = new Uri("http://stackoverflow.com").AddQuery("such", "method")
.AddQuery("wow", "soFluent");
// http://stackoverflow.com?such=method&wow=soFluent
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;
}
这是另一种(可能是多余的:-])方法。
其概念与本页的《吠陀经》答案相同(请看这里)。
但是这个类更有效,因为它只迭代所有key一次:当调用ToString时。
格式化代码也进行了简化和改进。
希望对大家有所帮助。
public sealed class QueryStringBuilder
{
public QueryStringBuilder()
{
this.inner = HttpUtility.ParseQueryString(string.Empty);
}
public QueryStringBuilder(string queryString)
{
this.inner = HttpUtility.ParseQueryString(queryString);
}
public QueryStringBuilder(string queryString, Encoding encoding)
{
this.inner = HttpUtility.ParseQueryString(queryString, encoding);
}
private readonly NameValueCollection inner;
public QueryStringBuilder AddKey(string key, string value)
{
this.inner.Add(key, value);
return this;
}
public QueryStringBuilder RemoveKey(string key)
{
this.inner.Remove(key);
return this;
}
public QueryStringBuilder Clear()
{
this.inner.Clear();
return this;
}
public override String ToString()
{
if (this.inner.Count == 0)
return string.Empty;
var builder = new StringBuilder();
for (int i = 0; i < this.inner.Count; i++)
{
if (builder.Length > 0)
builder.Append('&');
var key = this.inner.GetKey(i);
var values = this.inner.GetValues(i);
if (key == null || values == null || values.Length == 0)
continue;
for (int j = 0; j < values.Length; j++)
{
if (j > 0)
builder.Append('&');
builder.Append(HttpUtility.UrlEncode(key));
builder.Append('=');
builder.Append(HttpUtility.UrlEncode(values[j]));
}
}
return builder.ToString();
}
}