共用方式為

  • 發行項

使用 Try/Catch 區塊

在您將條件陳述式加入程式碼，以限制對報表伺服器的無效要求之後，應該透過使用 Try/Catch 區塊，來提供適當的例外狀況處理。這個技術可以針對無效的要求提供另一層的保護。如果對報表伺服器的要求是包含在 Try 區塊中，而且該要求造成報表伺服器擲回例外狀況，則在 Catch 區塊中會抓住例外狀況，因此可防止應用程式非預期地結束。一旦捕捉到例外狀況，您可以使用例外狀況來指示使用者執行不一樣的動作，或只是以適當的方式讓使用者知道已發生錯誤。接著您可以使用 Finally 區塊來清除任何資源。理想上，您應該產生一般的例外狀況處理計劃，來避免 Try/Catch 區塊不必要的複製。

下列範例使用 Try/Catch 區塊來增強例外狀況處理程式碼的可靠性。

// 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 = null;
      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
         warnings = rs.CreateReport(name, "/Samples", false, definition, null);
         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");
      }
   }
}