How to: Catch Exceptions

Article
10/16/2013

You place the sections of code that might throw exceptions in a try block and place code that handles exceptions in a catch block. The order of catch statements is important. When an exception occurs, it is passed up the stack and each catch block is given the opportunity to handle it. The catch block that should handle the exception is determined by matching the type of the exception to the name of the exception specified in the catch block. For example, the following catch block catches Simple Object Access Protocol (SOAP) exceptions:

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

If no type-specific catch block exists, the exception is caught by a general catch block, if one exists. For example, you can catch general exceptions by adding the following code:

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

You place catch blocks targeted to specific types of exceptions before a general exception.

The common language runtime catches exceptions that are not caught by a catch block. Depending on how the runtime is configured, either a debug dialog box appears, or the program stops executing and a dialog box with exception information appears. For information about debugging, see Debugging and Profiling Applications (https://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpguide/html/cpcondebuggingprofiling.asp).

For more information about how to handle exceptions, see Best Practices for Handling Exceptions (https://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpguide/html/cpconbestpracticesforhandlingexceptions.asp).

Example

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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How to: Catch Exceptions

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