c# - 如何解析来自 WebException 响应的内部异常

Question

我有 C# 代码对 OData Web 服务执行 POST，从而将记录插入到数据库中。如果出现异常，比如违反主键，我想捕获并记录错误信息。但是，该消息包含在 XML 中。这是我的异常处理程序:

catch (WebException ex)
{
  if (ex.Status == WebExceptionStatus.ProtocolError)
  {
      string responseText = string.Empty;

      using (Stream responseStream = ((HttpWebResponse)ex.Response).GetResponseStream())
      {
          using (StreamReader streamReader = new StreamReader(responseStream))
          {
              responseText = streamReader.ReadToEnd();
          }
      }
      Debug.WriteLine(responseText);
      return responseText;
  }
  else
  {
      Debug.WriteLine(ex.Message.ToString());
      return ex.Message.ToString();
  }
}

这是我在 responseText 中得到的内容:

<?xml version="1.0" encoding="utf-8" standalone="yes"?>
<error xmlns="http://schemas.microsoft.com/ado/2007/08/dataservices/metadata">
  <code></code>
  <message xml:lang="en-US">An error occurred while processing this request.</message>
  <innererror>
    <message>An error occurred while updating the entries. See the inner exception for details.</message>
    <type>System.Data.UpdateException</type>
    <stacktrace>   at System.Data.Mapping.Update.Internal.UpdateTranslator.Update(IEntityStateManager stateManager, IEntityAdapter adapter)&#xD;
   at System.Data.EntityClient.EntityAdapter.Update(IEntityStateManager entityCache)&#xD;
   at System.Data.Objects.ObjectContext.SaveChanges(SaveOptions options)&#xD;
   at System.Data.Services.Providers.ObjectContextServiceProvider.SaveChanges()&#xD;
   at System.Data.Services.DataService    1.HandleNonBatchRequest(RequestDescription description)&#xD;
   at System.Data.Services.DataService    1.HandleRequest()</stacktrace>
    <internalexception>
      <message>Violation of PRIMARY KEY constraint 'PK_Customer_CustomerId'. Cannot insert duplicate key in object 'VertexBilling.Customer'.&#xD;
The statement has been terminated.</message>
      <type>System.Data.SqlClient.SqlException</type>
      <stacktrace>   at System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection)&#xD;
   at System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection)&#xD;
   at System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning()&#xD;
   at System.Data.SqlClient.TdsParser.Run(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj)&#xD;
   at System.Data.SqlClient.SqlDataReader.ConsumeMetaData()&#xD;
   at System.Data.SqlClient.SqlDataReader.get_MetaData()&#xD;
   at System.Data.SqlClient.SqlCommand.FinishExecuteReader(SqlDataReader ds, RunBehavior runBehavior, String resetOptionsString)&#xD;
   at System.Data.SqlClient.SqlCommand.RunExecuteReaderTds(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, Boolean async)&#xD;
   at System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method, DbAsyncResult result)&#xD;
   at System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method)&#xD;
   at System.Data.SqlClient.SqlCommand.ExecuteReader(CommandBehavior behavior, String method)&#xD;
   at System.Data.SqlClient.SqlCommand.ExecuteDbDataReader(CommandBehavior behavior)&#xD;
   at System.Data.Common.DbCommand.ExecuteReader(CommandBehavior behavior)&#xD;
   at System.Data.Mapping.Update.Internal.DynamicUpdateCommand.Execute(UpdateTranslator translator, EntityConnection connection, Dictionary    2 identifierValues, List    1 generatedValues)&#xD;
   at System.Data.Mapping.Update.Internal.UpdateTranslator.Update(IEntityStateManager stateManager, IEntityAdapter adapter)</stacktrace>
    </internalexception>
  </innererror>
</error>

我需要从 innererror 中获取来自 internalexception 的消息。最简单的方法是什么？

Answer 1

您应该使用 XML 工具包，您已经在 .net 中使用了它，并且它消除了将 xml 视为文本时的歧义问题(这是一场等待发生的噩梦，在上面的 xml 中，您有两个消息节点)

1. 将字符串加载到 XmlDocument
2. 使用//error/innerError/internalexception/message xpath提取需要的节点

或者，您可以构建一小段代码，将 innerException 提取/反序列化为 Exception 实例，并可以将其重新用于其他调用。

如果你不知道怎么做，howler，我会搞砸的。