IntPtr.Zero 필드

정의

0으로 초기화된 포인터나 핸들을 나타내는 읽기 전용 필드입니다.A read-only field that represents a pointer or handle that has been initialized to zero.

public: static initonly IntPtr Zero;
public static readonly IntPtr Zero;
 staticval mutable Zero : nativeint
Public Shared ReadOnly Zero As IntPtr 

필드 값

IntPtr

설명

이 필드의 값은와 같지 않습니다 null .The value of this field is not equivalent to null. 이 필드를 사용 하 여의 인스턴스가 0이 IntPtr 아닌 값으로 설정 되었는지 여부를 효율적으로 확인할 수 있습니다.Use this field to efficiently determine whether an instance of IntPtr has been set to a value other than zero.

예를 들어, ip 변수가의 인스턴스인 경우를 가정 합니다 IntPtr .For example, assume the variable, ip, is an instance of IntPtr. 생성자에서 반환 하는 값과 비교 하 여 설정 되었는지 확인할 수 있습니다 (예: " if ip != new IntPtr(0)... ").You can determine if it has been set by comparing it to the value returned by a constructor, for example: " if ip != new IntPtr(0)... ". 그러나 생성자를 호출 하 여 초기화 되지 않은 포인터를 가져오는 것은 비효율적입니다.However, invoking a constructor to get an uninitialized pointer is inefficient. "" 또는 ""를 코딩 하는 것이 좋습니다 if ip != IntPtr.Zero... if !IntPtr.Zero.Equals(ip)... .It is better to code either " if ip != IntPtr.Zero... ", or " if !IntPtr.Zero.Equals(ip)... ".

관리 코드에서 Windows API를 호출 하는 경우 IntPtr.Zero null 인수가 포인터나가 될 것으로 예상 되는 경우 대신를 전달할 수 있습니다 null .When calling the Windows API from managed code, you can pass IntPtr.Zero instead of null if an argument is expected to be either a pointer or a null. 예를 들어 다음 Windows CreateFile 함수 호출은 IntPtr.Zero pSecurityAttributes 및 인수 값에 대해를 제공 합니다 hTemplateFile .For example, the following call to the Windows CreateFile function supplies IntPtr.Zero for the pSecurityAttributes and hTemplateFile argument values.

using Microsoft.Win32.SafeHandles;
using System;
using System.Runtime.InteropServices;

public class Example
{
   private const uint GENERIC_READ = 0x80000000;
   private const uint OPEN_EXISTING = 3;
   private const uint FILE_ATTRIBUTE_NORMAL = 128;
   private const uint FILE_FLAG_OVERLAPPED = 0x40000000;

   [DllImport("kernel32.dll", SetLastError = true, CharSet = CharSet.Unicode)]
   private static extern Microsoft.Win32.SafeHandles.SafeFileHandle CreateFile(
            string lpFileName, System.UInt32 dwDesiredAccess, System.UInt32 dwShareMode,
            IntPtr pSecurityAttributes, System.UInt32 dwCreationDisposition,
            System.UInt32 dwFlagsAndAttributes, IntPtr hTemplateFile);

   public static void Main()
   {
      SafeFileHandle hnd = CreateFile("CallOfTheWild.txt", GENERIC_READ, 0,
                                      IntPtr.Zero, OPEN_EXISTING,
                                      FILE_ATTRIBUTE_NORMAL | FILE_FLAG_OVERLAPPED,
                                      IntPtr.Zero);
      if (hnd.IsInvalid) {
            Exception ex = Marshal.GetExceptionForHR(Marshal.GetHRForLastWin32Error());
            Console.WriteLine("Attempt to open file failed:");
            Console.WriteLine("  {0}", ex.Message);
            return;
      }
      else {
         Console.WriteLine("File successfully opened.");
         hnd.Close();
      }
   }
}
// If the file cannot be found, the example displays the following output:
//    Attempt to open file failed:
//      The system cannot find the file specified. (Exception from HRESULT: 0x80070002)
Imports Microsoft.Win32.SafeHandles
Imports System.Runtime.InteropServices

Module Example
   Private Const GENERIC_READ As UInteger = 2147483648
   Private Const OPEN_EXISTING As UInteger = 3 
   Private Const FILE_ATTRIBUTE_NORMAL As UInteger = 128
   Private Const FILE_FLAG_OVERLAPPED As UInteger = &h40000000

   Private Declare Auto Function CreateFile Lib "Kernel32" Alias "CreateFileW" (
            lpFileName As String, dwDesiredAccess As UInt32, 
            dwShareMode As UInt32, pSecurityAttributes As IntPtr, 
            dwCreationDisposition As UInt32, dwFlagsAndAttributes As UInt32, 
            hTemplateFile As IntPtr) As SafeFileHandle

   Public Sub Main()
      Dim hnd As SafeFileHandle = CreateFile("CallOfTheWild.txt", GENERIC_READ, 0, 
                                             IntPtr.Zero, OPEN_EXISTING,
                                             FILE_ATTRIBUTE_NORMAL Or FILE_FLAG_OVERLAPPED, 
                                             IntPtr.Zero)
      If hnd.IsInvalid Then
         Dim ex As Exception = Marshal.GetExceptionForHR(Marshal.GetHRForLastWin32Error())
         Console.WriteLine("Attempt to open file failed:")
         Console.WriteLine("  {0}", ex.Message)
         Return           
      Else 
         Console.WriteLine("File successfully opened.")
         hnd.Close()     
      End If
   End Sub
End Module
' If the file cannot be found, the example displays the following output:
'    Attempt to open file failed:
'      The system cannot find the file specified. (Exception from HRESULT: 0x80070002)

참고

Zeronull 포인터나가 될 수 있는 반환 값 또는 매개 변수를 포함 하는 Windows API 함수의 경우와 동일 하지만는와 null Zero 동일 하지 않습니다 null .Although Zero is equivalent to null for Windows API functions with parameters or return values that can be either pointers or null, Zero is not equivalent to null. null메서드에 전달 하면 IntPtr.Zero.Equals 항상이 반환 false 됩니다.Passing null to the IntPtr.Zero.Equals method always returns false.

null반환 된 값을과 비교 하 여 포인터나을 반환 하는 WINDOWS API 함수 호출에서 반환 값을 테스트할 수도 있습니다 null IntPtr.Zero .You can also test for a null return value from Windows API function calls that return either a pointer or a null by comparing the returned value with IntPtr.Zero. 예를 들어 GetWindow 다음 예제에서 함수를 호출 하면 존재 하지 않는 창의 핸들을 검색 하려고 시도 합니다.For example, the call to the GetWindow function in the following example tries to retrieve the handle of a non-existent window. 비관리 코드에서 호출 된 경우이 함수는 null 를 반환 하지만, 관리 코드에서 호출 되는 경우을 반환 IntPtr.Zero 합니다.If it were called from unmanaged code, the function would return null, but when it is called from managed code, it returns IntPtr.Zero.

using System;
using System.Runtime.InteropServices;

public class Example
{
   private const int GW_OWNER = 4;

   [DllImport("user32", CharSet=CharSet.Auto, SetLastError=true, ExactSpelling=true)]
   public static extern IntPtr GetWindow(IntPtr hwnd, int wFlag);

   public static void Main()
   {
      IntPtr hwnd = new IntPtr(3);
      IntPtr hOwner = GetWindow(hwnd, GW_OWNER);
      if (hOwner == IntPtr.Zero)
         Console.WriteLine("Window not found.");
   }
}
// The example displays the following output:
//        Window not found.
Module Example
   Private Const GW_OWNER As Integer = 4

   Private Declare Function GetWindow Lib "user32" (hWnd As IntPtr, 
                            wFlag As Integer) As IntPtr 

   Public Sub Main()
      Dim hwnd = new IntPtr(3)
      Dim hOwner As IntPtr = GetWindow(hwnd, GW_OWNER)
      If hOwner = IntPtr.Zero Then
         Console.WriteLine("Window not found.")
      End If   
   End Sub
End Module
' The example displays the following output:
'       Window not found.

적용 대상