WebRequest System.NotSupportedException

Question

用 monodevelop 写的：

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：http://yahoo.com/ 在 System.Net.WebRequest.GetCreator（System.String 前缀）[0x00000] 中：0 在 System.Net.WebRequest.Create (System.Uri requestUri) [0x00000] in :0 在 System.Net.WebRequest.Create (System.String requestUriString) [0x00000] in :0 在 CNBC.Research.LookupUtil.downloadStockHistory (System.String 符号) [0x00000] in :0 在 CNBC.MainClass.Main (System.String[] args) [0x00000] in :0 [错误] 致命的未处理异常：System.NotSupportedException：http://yahoo.com/ 在 System.Net.WebRequest.GetCreator（System.String 前缀）[0x00000] 中：0 在 System.Net.WebRequest.Create (System.Uri requestUri) [0x00000] in :0 在 System.Net.WebRequest.Create (System.String requestUriString) [0x00000] in :0 在 CNBC.Research.Hello.world (System.String 符号) [0x00000] in :0 在 CNBC.MainClass.Main (System.String[] args) [0x00000] in :0

我相信这是因为它不知道http 是什么，但我不知道如何添加它。

编辑：

这可能会说明问题。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

我应该为 .NET 3.5 运行 3.5 版吗？

Answer 1

请尝试以下代码 sn-p。

   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 ();

      }

或

 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

当我尝试将我的应用程序与单运行时捆绑在一起以在未安装开箱即用的运行时的机器上使用时，我遇到了这种情况。

解决方案是将 App.config 文件添加到我的项目中，其中包含以下内容（从我安装的单声道版本的 machine.config 文件中复制的部分）

<?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>

希望这能给你一个线索！