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使用 Try/Catch 块

在通过向代码添加条件语句以限制对于报表服务器的无效请求之后，应通过使用 try/catch 块提供适当的异常处理。此方法从另一个层面来防止无效的请求。如果对于报表服务器的请求包含在 try 块中，并且该请求导致报表服务器引发异常，则将在 catch 块中捕获此异常，从而防止应用程序意外终止。一旦捕获了异常，您就可以使用该异常来指导用户以不同方式操作，或者只是以友好的方式让用户知道已发生了错误。然后，您可以使用 finally 块来清除任何资源。在理想情况下，应生成一个常规异常处理计划以避免不必要地重复 try/catch 块。

以下示例使用 try/catch 块以增强异常处理代码的可靠性。

// C#
private void PublishReport()
{
   int index;
   string reservedChar;
   string message;

   // Check the text value of the name text box for "/",
   // a reserved character
   index = nameTextBox.Text.IndexOf(@"/");

   if ( index != -1) // The text contains the character
   {
      reservedChar = nameTextBox.Text.Substring(index, 1);
      // Build a user-friendly error message
      message = "The name of the report cannot contain the reserved character " +
         "\"" + reservedChar + "\". " +
         "Please enter a valid name for the report. " +
         "For more information about reserved characters, " +
         "consult the online documentation";

      MessageBox.Show(message, "Invalid Input Error");
   }
   else // Publish the report
   {
      Byte[] definition = null;
      Warning[] warnings = {};
      string name = nameTextBox.Text;

      try
      {
         FileStream stream = File.OpenRead("MyReport.rdl");
         definition = new Byte[stream.Length];
         stream.Read(definition, 0, (int) stream.Length);
         stream.Close();
         // Create report with user-defined name
         rs.CreateCatalogItem("Report", name, "/Samples", false, definition, null, out warnings);
         MessageBox.Show("Report: {0} created successfully", name);
      }

      // Catch expected exceptions beginning with the most specific,
      // moving to the least specific
      catch(IOException ex)
      {
         MessageBox.Show(ex.Message, "File IO Exception");
      }

      catch (SoapException ex)
      {
         // The exception is a SOAP exception, so use
         // the Detail property's Message element.
         MessageBox.Show(ex.Detail["Message"].InnerXml, "SOAP Exception"); 
      }

      catch (Exception ex)
      {
         MessageBox.Show(ex.Message, "General Exception");
      }
   }
}