如何创建扩展方法，允许您以这样流畅的风格添加参数?

string a = "http://www.somedomain.com/somepage.html"
    .AddQueryParam("A", "TheValueOfA")
    .AddQueryParam("B", "TheValueOfB")
    .AddQueryParam("Z", "TheValueOfZ");

string b = new StringBuilder("http://www.somedomain.com/anotherpage.html")
    .AddQueryParam("A", "TheValueOfA")
    .AddQueryParam("B", "TheValueOfB")
    .AddQueryParam("Z", "TheValueOfZ")
    .ToString(); 

下面是使用字符串的重载:

public static string AddQueryParam(
    this string source, string key, string value)
{
    string delim;
    if ((source == null) || !source.Contains("?"))
    {
        delim = "?";
    }
    else if (source.EndsWith("?") || source.EndsWith("&"))
    {
        delim = string.Empty;
    }
    else
    {
        delim = "&";
    }

    return source + delim + HttpUtility.UrlEncode(key)
        + "=" + HttpUtility.UrlEncode(value);
}

这里是使用StringBuilder的重载:

public static StringBuilder AddQueryParam(
    this StringBuilder source, string key, string value)
{
    bool hasQuery = false;
    for (int i = 0; i < source.Length; i++)
    {
        if (source[i] == '?')
        {
            hasQuery = true;
            break;
        }
    }

    string delim;
    if (!hasQuery)
    {
        delim = "?";
    }
    else if ((source[source.Length - 1] == '?')
        || (source[source.Length - 1] == '&'))
    {
        delim = string.Empty;
    }
    else
    {
        delim = "&";
    }

    return source.Append(delim).Append(HttpUtility.UrlEncode(key))
        .Append("=").Append(HttpUtility.UrlEncode(value));
}

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

HttpValueCollection的可链接包装类:

namespace System.Web.Mvc {
    public class QueryStringBuilder {
        private NameValueCollection collection;
        public QueryStringBuilder() {
            collection = System.Web.HttpUtility.ParseQueryString(string.Empty);
        }
        public QueryStringBuilder Add(string key, string value) {
            collection.Add(key, value);
            return this;
        }
        public QueryStringBuilder Remove(string key) {
            collection.Remove(key);
            return this;
        }
        public string this[string key] {
            get { return collection[key]; }
            set { collection[key] = value; }
        }
        public string ToString() {
            return collection.ToString();
        }
    }
}

使用示例:

QueryStringBuilder parameters = new QueryStringBuilder()
    .Add("view", ViewBag.PageView)
    .Add("page", ViewBag.PageNumber)
    .Add("size", ViewBag.PageSize);
string queryString = parameters.ToString();

这与公认的答案完全相同，只是稍微更紧凑:

private string ToQueryString(NameValueCollection nvc)
{
    return "?" + string.Join("&", nvc.AllKeys.Select(k => string.Format("{0}={1}", 
        HttpUtility.UrlEncode(k), 
        HttpUtility.UrlEncode(nvc[k]))));
}

奇怪的是没有人提到来自asp.net . core的QueryBuilder。

当你有一个重复键的查询，比如?filter=a&filter=b，它会很有用

var qb = new QueryBuilder();
qb.Add("filter", new string[] {"A", "B"});

然后你只需要将qb添加到URI中，它就会自动转换为字符串。

https://learn.microsoft.com/en-us/dotnet/api/microsoft.aspnetcore.http.extensions.querybuilder?view=aspnetcore-5.0

public string UrlQueryStr(object data)
{
    if (data == null)
        return string.Empty;

    object val;
    StringBuilder sb = new StringBuilder();

    foreach (PropertyDescriptor prop in TypeDescriptor.GetProperties(data))
    {
        if ((val = prop.GetValue(data)) != null)
        {
            sb.AppendFormat("{0}{1}={2}", sb.Length == 0 ? '?' : '&',
                HttpUtility.UrlEncode(prop.Name), HttpUtility.UrlEncode(val.ToString()));
        }
    }
    return sb.ToString();
}