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?
这是我最近的记录。由于种种原因,我不喜欢其他的,所以我自己写了一个。
这个版本的特点:
Use of StringBuilder only. No ToArray() calls or other extension methods. It doesn't look as pretty as some of the other responses, but I consider this a core function so efficiency is more important than having "fluent", "one-liner" code which hide inefficiencies.
Handles multiple values per key. (Didn't need it myself but just to silence Mauricio ;)
public string ToQueryString(NameValueCollection nvc)
{
StringBuilder sb = new StringBuilder("?");
bool first = true;
foreach (string key in nvc.AllKeys)
{
foreach (string value in nvc.GetValues(key))
{
if (!first)
{
sb.Append("&");
}
sb.AppendFormat("{0}={1}", Uri.EscapeDataString(key), Uri.EscapeDataString(value));
first = false;
}
}
return sb.ToString();
}
示例使用
var queryParams = new NameValueCollection()
{
{ "x", "1" },
{ "y", "2" },
{ "foo", "bar" },
{ "foo", "baz" },
{ "special chars", "? = &" },
};
string url = "http://example.com/stuff" + ToQueryString(queryParams);
Console.WriteLine(url);
输出
http://example.com/stuff?x=1&y=2&foo=bar&foo=baz&special%20chars=%3F%20%3D%20%26
这是我最近的记录。由于种种原因,我不喜欢其他的,所以我自己写了一个。
这个版本的特点:
Use of StringBuilder only. No ToArray() calls or other extension methods. It doesn't look as pretty as some of the other responses, but I consider this a core function so efficiency is more important than having "fluent", "one-liner" code which hide inefficiencies.
Handles multiple values per key. (Didn't need it myself but just to silence Mauricio ;)
public string ToQueryString(NameValueCollection nvc)
{
StringBuilder sb = new StringBuilder("?");
bool first = true;
foreach (string key in nvc.AllKeys)
{
foreach (string value in nvc.GetValues(key))
{
if (!first)
{
sb.Append("&");
}
sb.AppendFormat("{0}={1}", Uri.EscapeDataString(key), Uri.EscapeDataString(value));
first = false;
}
}
return sb.ToString();
}
示例使用
var queryParams = new NameValueCollection()
{
{ "x", "1" },
{ "y", "2" },
{ "foo", "bar" },
{ "foo", "baz" },
{ "special chars", "? = &" },
};
string url = "http://example.com/stuff" + ToQueryString(queryParams);
Console.WriteLine(url);
输出
http://example.com/stuff?x=1&y=2&foo=bar&foo=baz&special%20chars=%3F%20%3D%20%26
这里有很多很好的答案,但对于使用现代c#的人来说,这可能是一个很好的实用程序类。
public class QueryParamBuilder
{
private readonly Dictionary<string, string> _fields = new();
public QueryParamBuilder Add(string key, string value)
{
_fields.Add(key, value);
return this;
}
public string Build()
{
return $"?{String.Join("&", _fields.Select(pair => $"{HttpUtility.UrlEncode(pair.Key)}={HttpUtility.UrlEncode(pair.Value)}"))}";
}
public static QueryParamBuilder New => new();
}
我在这里使用了一个内部Dictionary,因为字典在内部是可枚举的键值对,这使得遍历它们比NameValueCollection容易得多。
那么查询字符串本身就是一个简单的带有连接的插值字符串。
另外,我为构造函数提供了一个静态接口,使构造新的构造器非常容易,并且只允许一个公开的方法Add来添加新的查询参数值。最后,使用Build()终止链以实际获得最终字符串。
下面是它用法的一个例子
var queryString = QueryParamBuilder.New
.Add("id", "0123")
.Add("value2", 1234.ToString())
.Add("valueWithSpace","value with spa12!@#@!ce")
.Build();
结果和预期的一样
?id=0123&value2=1234&valueWithSpace=value+with+spa12!%40%23%40!ce
希望你们中的一些人会觉得这个很好很优雅。
Flurl[披露:我是作者]支持通过匿名对象(以及其他方式)构建查询字符串:
var url = "http://www.some-api.com".SetQueryParams(new
{
api_key = ConfigurationManager.AppSettings["SomeApiKey"],
max_results = 20,
q = "Don't worry, I'll get encoded!"
});
可选的Flurl。Http companion lib允许您在相同的流畅调用链上执行Http调用,将其扩展为一个成熟的REST客户端:
T result = await "https://api.mysite.com"
.AppendPathSegment("person")
.SetQueryParams(new { ap_key = "my-key" })
.WithOAuthBearerToken("MyToken")
.PostJsonAsync(new { first_name = firstName, last_name = lastName })
.ReceiveJson<T>();
完整的软件包在NuGet上可用:
PM>安装包Flurl。Http
或者只是独立的URL构建器:
PM>安装包Flurl
基于扩展方法的快速版本:
class Program
{
static void Main(string[] args)
{
var parameters = new List<KeyValuePair<string, string>>
{
new KeyValuePair<string, string>("A", "AValue"),
new KeyValuePair<string, string>("B", "BValue")
};
string output = "?" + string.Join("&", parameters.ConvertAll(param => param.ToQueryString()).ToArray());
}
}
public static class KeyValueExtensions
{
public static string ToQueryString(this KeyValuePair<string, string> obj)
{
return obj.Key + "=" + HttpUtility.UrlEncode(obj.Value);
}
}
可以使用where子句来选择将哪些参数添加到字符串中。