例外をキャッチする

例外が発生する可能性があるコードのセクションを try ブロックに配置するとともに、例外を処理するコードを catch ブロックに配置します。 catch ステートメントの順序は重要です。例外が発生すると、スタックが渡され、各 catch ブロックに処理の機会が与えられます。例外を処理する必要がある catch ブロックは、例外の種類と catch ブロックで指定された例外名を照合して決定されます。たとえば、次の catch ブロックは Simple Object Access Protocol (SOAP) の例外をキャッチします。

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

Catch e As SoapException
  Console.WriteLine("SOAP Exception Error Code: {0}", e.SubCode.Code.Name)
  Console.WriteLine("SOAP Exception Message is: {0}", e.Message)
End Try

型固有の catch ブロックが存在しない場合、例外が存在する場合は、一般的な catch ブロックによってキャッチされます。たとえば、次のコードを追加することで汎用的な例外をキャッチできます。

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

Catch e As Exception
  Console.WriteLine("Exception Message: {0}", e.Message)
End Try

特定の型の例外を対象とする catch ブロックは、一般的な例外の前に配置します。共通言語ランタイムは、catch ブロックによってキャッチされない例外をキャッチします。ランタイムの構成次第で、デバッグのダイアログボックスが表示されるか、プログラムの実行が停止して例外情報のダイアログボックスが表示されます。

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();
    }
  }
}

Imports System
Imports System.Text
Imports System.Web.Services.Protocols
Imports ExcelWebService.myserver02
Namespace ExcelWebService
  Friend Class WebService
    <STAThread> _
    Shared Sub Main(ByVal args() As String)
      ' Instantiate the Web service and make a status array object
      Dim xlservice As New ExcelService()
      Dim outStatus() As Status
      Dim rangeCoordinates As New RangeCoordinates()
      Dim sheetName As String = "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";
      Dim targetWorkbookPath As String = "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.
        Dim sessionId As String = xlservice.OpenWorkbook(targetWorkbookPath, "en-US", "en-US", 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

        Dim rangeResult1() As Object = xlservice.GetRange(sessionId, sheetName, rangeCoordinates, False, outStatus)
        Console.WriteLine("Total rows in range: " &amp; rangeResult1.Length)

        Console.WriteLine("Sum in last column is: " &amp; (CType(rangeResult1(2), Object()))(3))

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

      Catch e As Exception
        Console.WriteLine("Exception Message: {0}", e.Message)
      End Try
      Console.ReadLine()
    End Sub
  End Class
End Namespace

例外をキャッチする

例

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