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

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"));

其他回答

编辑-正如评论中指出的那样,这不是正确的方法。

有这样一个类——URI类。提供统一资源标识符(URI)的对象表示,并方便访问URI的各个部分。(微软文档)。

下面的例子创建了一个Uri类的实例,并使用它来创建一个WebRequest实例。

c#示例

Uri siteUri = new Uri("http://www.contoso.com/");

WebRequest wr = WebRequest.Create(siteUri);

看一下,这个类上有很多方法。

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"));

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);
}

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"

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;
}