无法从“字符串”转换为“'System.Collections.Specialized.NameValueCollection‘”

Question

我正在开发一个asp.net mvc-4 web应用程序，我有以下方法将json对象上传到第三部分应用程序。其中，我想将url标题设置为application/x-www-form-urlencoded:-

using (WebClient wc = new WebClient()) 
                {
                    string url = currentURL + "resources?AUTHTOKEN=" + pmtoken;
                    Uri uri = new Uri(url);

                    wc.Headers.Add(HttpRequestHeader.ContentType, "application/x-www-form-urlencoded");

                    var encodedJson = WebUtility.UrlEncode(data);
                    crudoutput = wc.UploadValues(uri, "INPUT_DATA=" + encodedJson);
                }

但上述情况会引起以下错误：

无法从“字符串”转换为“'System.Collections.Specialized.NameValueCollection‘” 'System.Net.WebClient.UploadValues(System.Uri，System.Collections.Specialized.NameValueCollection)‘的最佳重载方法匹配有一些无效的参数

所以，谁能在这个问题上放弃吗？

Answer 1

错误很明显。UploadValues采用NameValueCollection而不是字符串https://msdn.microsoft.com/en-us/library/9w7b4fz7(v=vs.110).aspx

你的代码应该是

var nvc = new NameValueCollection();

nvc.Add("INPUT_DATA", encodedJson);

crudoutput = wc.UploadValues(uri, nvc);

更新

您可以尝试UploadString：https://msdn.microsoft.com/en-us/library/0645045y(v=vs.110).aspx

crudoutput = wc.UploadString(uri, "INPUT_DATA=" + encodedJson);

Answer 2

您需要定义一个新的NameValueCollection并将其传递给UploadValues

crudoutput = wc.UploadValues(uri, new NameValueCollection()
{
    { "INPUT_DATA", encodedJson }
});

Answer 3

WebClient UploadValues方法将NameValueCollection而不是string作为参数。

所以你可以试试这个

    using (WebClient wc = new WebClient()) 
     {
         string url = currentURL + "resources?AUTHTOKEN=" + pmtoken;
         Uri uri = new Uri(url);       
         wc.Headers.Add(HttpRequestHeader.ContentType, "application/x-www-form-urlencoded");

         var encodedJson = WebUtility.UrlEncode(data);

         NameValueCollection myNameValueCollection = new NameValueCollection();
         myNameValueCollection.Add("INPUT_DATA",encodedJson);
         crudoutput = wc.UploadValues(uri, myNameValueCollection);
     }