WebRequest System.NotSupportedException

Question

在monodevelop中写成这样：

using System;
using System.Net;
using System.Net.Http;

namespace Hello
{
    public class Hello
    {
        public Hello () {}

        public static WebResponse world(string symbol) {
            WebRequest request = WebRequest.Create("http://yahoo.com");
            WebResponse response = request.GetResponse ();
        }
    }
}

在运行时获取此异常：

未处理的异常：System.NotSupportedException：System.Net.WebRequest.GetCreator上的http://yahoo.com/（System.String前缀）[0x00000]，System.Net.WebRequest.Create上的：0（System.Uri requestUri）[在CNBC.Research.LookupUtil.downloadStockHistory（System.String符号）在0处，在CNBC.MainClass的：0处，在System.Net.WebRequest.Create（0.在00000. 0x00000]在System.Net.WebRequest.Create（System.String requestUriString）[0x00000]在[0x00000]主（System.String []参数）[0x00000]在：0 [ERROR]致命未处理的异常：System.NotSupportedException： http://yahoo.com/在System.Net.WebRequest.GetCreator（System.String前缀）[0x00000 ]在System.Net.WebRequest.Create（System.Uri requestUri）的：0中[0x00000]在System.Net.WebRequest.Create（System.String requestUriString）的：0中的CN0.CN（0x00000）在CNBC.Research.Hello .world（System.String符号）[0x00000]在CNBC.MainClass.Main的：0中[System.String [] args）[0x00000]在：0的状态

我相信是因为它不知道什么是http ，但是我不知道如何添加它。

编辑：

这可以揭示问题所在。 可能是因为我运行了错误的版本？ 我也收到此错误：

警告：此应用程序支持的运行时版本不可用。 使用默认运行时：v4.0.30319

我应该运行.NET 3.5的3.5版吗？

Answer 1

请尝试以下代码片段。

   public static WebResponse world(string symbol) {
        // Create a new 'Uri' object with the specified string.
        Uri myUri =new Uri("http://yahoo.com");
        // Create a new request to the above mentioned URL. 
        WebRequest request= WebRequest.Create(myUri);
        // Assign the response object of 'WebRequest' to a 'WebResponse' variable.
        WebResponse response = request.GetResponse ();

      }

要么

 public static WebResponse world(string symbol) {
        // Create a new 'Uri' object with the specified string.
        Uri myUri =new Uri("http://yahoo.com");
        // Create a new request to the above mentioned URL. 
        WebRequest request= CreateWebRequest(myUri);
        // Assign the response object of 'WebRequest' to a 'WebResponse' variable.
        WebResponse response = request.GetResponse ();

      }


private static HttpWebRequest CreateWebRequest(Uri uri)
{
 var type = Type.GetType("System.Net.HttpRequestCreator, System, Version=4.0.0.0,Culture=neutral, PublicKeyToken=b77a5c561934e089");
    var creator = Activator.CreateInstance(type,nonPublic:true) as IWebRequestCreate;
    return creator.Create(uri) as HttpWebRequest;
}

Answer 2

一旦我尝试将应用程序与Mono Runtime捆绑在一起以在没有开箱即用安装的机器上使用时，我就遇到了这种情况。

解决方案是使用以下内容将App.config文件添加到我的项目中（已安装单声道版本的machine.config文件中的复制部分）

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <configSections>
    <sectionGroup name="system.net" type="System.Net.Configuration.NetSectionG

    roup, System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089">
            <section name="authenticationModules" type="System.Net.Configuration.AuthenticationModulesSection, System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" />
            <section name="connectionManagement" type="System.Net.Configuration.ConnectionManagementSection, System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" />
            <section name="defaultProxy" type="System.Net.Configuration.DefaultProxySection, System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" />
            <sectionGroup name="mailSettings" type="System.Net.Configuration.MailSettingsSectionGroup, System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089">
                <section name="smtp" type="System.Net.Configuration.SmtpSection, System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" />
            </sectionGroup>
            <section name="requestCaching" type="System.Net.Configuration.RequestCachingSection, System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" />
            <section name="settings" type="System.Net.Configuration.SettingsSection, System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" />
            <section name="webRequestModules" type="System.Net.Configuration.WebRequestModulesSection, System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" />
        </sectionGroup>
      </configSections>

      <system.net>
        <authenticationModules>
            <add type="System.Net.BasicClient, System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" />
            <add type="System.Net.DigestClient, System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" />
            <add type="System.Net.NtlmClient, System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" />
        </authenticationModules>
        <webRequestModules>
            <add prefix="http" type="System.Net.HttpRequestCreator, System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" />
            <add prefix="https" type="System.Net.HttpRequestCreator, System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" />
            <add prefix="file" type="System.Net.FileWebRequestCreator, System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" />
            <add prefix="ftp" type="System.Net.FtpRequestCreator, System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" />
        </webRequestModules>
        <settings>
          <ipv6 enabled="false"/>
          <servicePointManager checkCertificateName="false" checkCertificateRevocationList="false" />
        </settings>
      </system.net>


    </configuration>

希望这会给你一个线索！