如何：捕获异常

项目
06/15/2015

将可能引发异常的代码段放在 Try 块中，而将处理异常的代码放在 Catch 块中。Catch 语句的顺序很重要。发生异常时，异常沿堆栈向上传递，每个 Catch 块都有机会处理它。通过将异常类型与 Catch 块中指定的异常名称相匹配，可确定处理异常的 Catch 块。例如，以下 Catch 块将捕获简单对象访问协议 (SOAP) 异常：

catch (SoapException e)
{
    Console.WriteLine("SOAP Exception Error Code: {0}", 
        e.SubCode.Code.Name);
    Console.WriteLine("SOAP Exception Message is: {0}", 
        e.Message);
}

如果不存在特定类型的 Catch 块，则由可能存在的常规 Catch 块来捕捉异常。例如，您可以通过添加以下代码来捕获一般异常：

catch (Exception e)
{
    Console.WriteLine("Exception Message: {0}", e.Message);
}

将针对特定类型异常的 Catch 块放在一般异常之前。

公共语言运行库将捕捉 Catch 块未捕捉的异常。根据运行库的配置，可能会显示一个调试对话框，或者停止执行程序并显示一个包含异常信息的对话框。有关调试的详细信息，请参阅Debugging and Profiling Applications（https://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpguide/html/cpcondebuggingprofiling.asp）。

有关如何处理异常的详细信息，请参阅Best Practices for Handling Exceptions （https://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpguide/html/cpconbestpracticesforhandlingexceptions.asp）。

示例

using System;
using System.Text;
using System.Web.Services.Protocols;
using ExcelWebService.myserver02;
namespace ExcelWebService
{
    class WebService
    {
        [STAThread]
        static void Main(string[] args)
        {
            // Instantiate the Web service and make a status array object
            ExcelService xlservice = new ExcelService();
            Status[] outStatus;
            RangeCoordinates rangeCoordinates = new RangeCoordinates();
            string sheetName = "Sheet1";

            // Set the path to the workbook to open.
            // TODO: Change the path to the workbook
            // to point to a workbook you have access to.
            // The workbook must be in a trusted location.
            // If workbookPath is a UNC path, the application 
            // must be on the same computer as the server.
            // string targetWorkbookPath = 
            // @"\\MyServer\myxlfiles\Formulas.xlsx";
            string targetWorkbookPath = 
            "http://myserver02/DocLib/Shared%20Documents/Basic1.xlsx";
            // Set credentials for requests
            xlservice.Credentials = 
               System.Net.CredentialCache.DefaultCredentials;

            try
            {
                // Call the OpenWorkbook method and point to the 
                // trusted location of the workbook to open.
                string sessionId = xlservice.OpenWorkbook(targetWorkbookPath, "en-US", "en-US", out outStatus);
                Console.WriteLine("sessionID : {0}", sessionId);
                // Prepare object to define range coordinates, 
                // and call the GetRange method.
                rangeCoordinates.Column = 0;
                rangeCoordinates.Row = 0;
                rangeCoordinates.Height = 18;
                rangeCoordinates.Width = 10;

                object[] rangeResult1 = xlservice.GetRange(sessionId, sheetName, rangeCoordinates, false, out outStatus);
                Console.WriteLine("Total rows in range: " + rangeResult1.Length);

                Console.WriteLine("Sum in last column is: " + ((object[])rangeResult1[2])[3]);

               // Close the workbook. This also closes the session.
                xlservice.CloseWorkbook(sessionId);
            }
            catch (SoapException e)
            {
                Console.WriteLine("SOAP Exception Error Code: {0}", 
                    e.SubCode.Code.Name);
                Console.WriteLine("SOAP Exception Message is: {0}", 
                    e.Message);
            }

            catch (Exception e)
            {
                Console.WriteLine("Exception Message: {0}", e.Message);
            }
            Console.ReadLine();
        }
    }
}

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如何：捕获异常

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