感谢“Darin Dimitrov”，这是扩展方法。

 public static partial class Ext
{
    public static Uri GetUriWithparameters(this Uri uri,Dictionary<string,string> queryParams = null,int port = -1)
    {
        var builder = new UriBuilder(uri);
        builder.Port = port;
        if(null != queryParams && 0 < queryParams.Count)
        {
            var query = HttpUtility.ParseQueryString(builder.Query);
            foreach(var item in queryParams)
            {
                query[item.Key] = item.Value;
            }
            builder.Query = query.ToString();
        }
        return builder.Uri;
    }

    public static string GetUriWithparameters(string uri,Dictionary<string,string> queryParams = null,int port = -1)
    {
        var builder = new UriBuilder(uri);
        builder.Port = port;
        if(null != queryParams && 0 < queryParams.Count)
        {
            var query = HttpUtility.ParseQueryString(builder.Query);
            foreach(var item in queryParams)
            {
                query[item.Key] = item.Value;
            }
            builder.Query = query.ToString();
        }
        return builder.Uri.ToString();
    }
}

接受答案的好部分，修改为使用UriBuilder.Uri.ParseQueryString()而不是HttpUtility.ParseQueryString():

var builder = new UriBuilder("http://example.com");
var query = builder.Uri.ParseQueryString();
query["foo"] = "bar<>&-baz";
query["bar"] = "bazinga";
builder.Query = query.ToString();
string url = builder.ToString();

避免taras中描述的双重编码问题。roshko的答案，并保持容易使用查询参数的可能性，你可以使用uriBuilder.Uri.ParseQueryString()而不是HttpUtility.ParseQueryString()。

您可能想看看Flurl[披露:我是作者]，这是一个流畅的URL构建器，带有可选的配套库，可以将其扩展为一个成熟的REST客户机。

var result = await "https://api.com"
    // basic URL building:
    .AppendPathSegment("endpoint")
    .SetQueryParams(new {
        api_key = ConfigurationManager.AppSettings["SomeApiKey"],
        max_results = 20,
        q = "Don't worry, I'll get encoded!"
    })
    .SetQueryParams(myDictionary)
    .SetQueryParam("q", "overwrite q!")

    // extensions provided by Flurl.Http:
    .WithOAuthBearerToken("token")
    .GetJsonAsync<TResult>();

查看文档了解更多细节。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

或者简单地使用我的Uri扩展

Code

public static Uri AttachParameters(this Uri uri, NameValueCollection parameters)
{
    var stringBuilder = new StringBuilder();
    string str = "?";
    for (int index = 0; index < parameters.Count; ++index)
    {
        stringBuilder.Append(str + parameters.AllKeys[index] + "=" + parameters[index]);
        str = "&";
    }
    return new Uri(uri + stringBuilder.ToString());
}

使用

Uri uri = new Uri("http://www.example.com/index.php").AttachParameters(new NameValueCollection
                                                                           {
                                                                               {"Bill", "Gates"},
                                                                               {"Steve", "Jobs"}
                                                                           });

结果

http://www.example.com/index.php?Bill=Gates&Steve=Jobs

我正在开发的RFC 6570 URI Template库能够执行此操作。所有编码都按照RFC为您处理。在撰写本文时，beta版本已经可用，它不是稳定的1.0版本的唯一原因是文档没有完全满足我的期望(参见问题#17、#18、#32、#43)。

你可以单独构建一个查询字符串:

UriTemplate template = new UriTemplate("{?params*}");
var parameters = new Dictionary<string, string>
  {
    { "param1", "value1" },
    { "param2", "value2" },
  };
Uri relativeUri = template.BindByName(parameters);

或者你可以构建一个完整的URI:

UriTemplate template = new UriTemplate("path/to/item{?params*}");
var parameters = new Dictionary<string, string>
  {
    { "param1", "value1" },
    { "param2", "value2" },
  };
Uri baseAddress = new Uri("http://www.example.com");
Uri relativeUri = template.BindByName(baseAddress, parameters);