LayoutKind 列舉

定義

命名空間:

System.Runtime.InteropServices

組件:

System.Runtime.dll

控制匯出至 Unmanaged 程式碼時的物件配置。

public enum class LayoutKind

public enum LayoutKind

type LayoutKind = 

Public Enum LayoutKind

繼承

Object

ValueType

Enum

LayoutKind

欄位

Auto	3	執行階段會自動選擇 Unmanaged 記憶體中物件成員的適當配置。 使用這個列舉成員定義的物件不可以在 Managed 程式碼以外公開。 嘗試這麼做會產生例外狀況。
Explicit	2	Unmanaged 記憶體中每個物件成員的精確位置是被明確地控制（受制於Pack欄位的設定）。 每個成員必須使用 FieldOffsetAttribute，表示該欄位在型別中的位置。
Sequential	0	物件的成員是依序配置的，其順序即是將它們匯出至 Unmanaged 記憶體時所出現的順序。 成員是根據 Pack 中所指定的封裝來配置。

範例

下列範例顯示函式的 PtInRect Managed 宣告，它會檢查某個點是否位於矩形內，並定義 Point 具有循序配置的結構，以及 Rect 具有明確配置的結構。

enum class Bool
{
   False = 0,
   True
};


[StructLayout(LayoutKind::Sequential)]
value struct Point
{
public:
   int x;
   int y;
};


[StructLayout(LayoutKind::Explicit)]
value struct Rect
{
public:

   [FieldOffset(0)]
   int left;

   [FieldOffset(4)]
   int top;

   [FieldOffset(8)]
   int right;

   [FieldOffset(12)]
   int bottom;
};

ref class NativeMethods
{
public:

   [DllImport("user32.dll",CallingConvention=CallingConvention::StdCall)]
   static Bool PtInRect( Rect * r, Point p );
};

int main()
{
   try
   {
      Bool bPointInRect = (Bool)0;
      Rect myRect = Rect(  );
      myRect.left = 10;
      myRect.right = 100;
      myRect.top = 10;
      myRect.bottom = 100;
      Point myPoint = Point(  );
      myPoint.x = 50;
      myPoint.y = 50;
      bPointInRect = NativeMethods::PtInRect(  &myRect, myPoint );
      if ( bPointInRect == Bool::True )
            Console::WriteLine( "Point lies within the Rect" );
      else
            Console::WriteLine( "Point did not lie within the Rect" );
   }
   catch ( Exception^ e ) 
   {
      Console::WriteLine( "Exception : {0}", e->Message );
   }

}

enum Bool
{
   False = 0,
   True
};
[StructLayout(LayoutKind.Sequential)]
public struct Point
{
   public int x;
   public int y;
}

[StructLayout(LayoutKind.Explicit)]
public struct Rect
{
   [FieldOffset(0)] public int left;
   [FieldOffset(4)] public int top;
   [FieldOffset(8)] public int right;
   [FieldOffset(12)] public int bottom;
}

internal static class NativeMethods
{
   [DllImport("user32.dll", CallingConvention=CallingConvention.StdCall)]
   internal static extern Bool PtInRect(ref Rect r, Point p);
};

class TestApplication
{
   public static void Main()
   {
      try
      {
         Bool bPointInRect = 0;
         Rect myRect = new Rect();
         myRect.left = 10;
         myRect.right = 100;
         myRect.top = 10;
         myRect.bottom = 100;
         Point myPoint = new Point();
         myPoint.x = 50;
         myPoint.y = 50;
         bPointInRect = NativeMethods.PtInRect(ref myRect, myPoint);
         if(bPointInRect == Bool.True)
            Console.WriteLine("Point lies within the Rect");
         else
            Console.WriteLine("Point did not lie within the Rect");
      }
      catch(Exception e)
      {
         Console.WriteLine("Exception : " + e.Message);
      }
   }
}

'  The program shows a managed declaration of the PtInRect function and defines Point
'  structure with sequential layout and Rect structure with explicit layout. The PtInRect
'  checks the point lies within the rectangle or not.
Imports System.Runtime.InteropServices

   Enum Bool
      [False] = 0
      [True]
   End Enum 
   <StructLayout(LayoutKind.Sequential)>  _
   Public Structure Point
      Public x As Integer
      Public y As Integer
   End Structure 
   
   <StructLayout(LayoutKind.Explicit)>  _   
   Public Structure Rect
      <FieldOffset(0)> Public left As Integer
      <FieldOffset(4)> Public top As Integer
      <FieldOffset(8)> Public right As Integer
      <FieldOffset(12)> Public bottom As Integer
   End Structure 
   
   
   Friend Class NativeMethods
      
      <DllImport("user32.dll", CallingConvention := CallingConvention.StdCall)>  _
      Friend Shared Function PtInRect(ByRef r As Rect, p As Point) As Bool
      End Function	
   End Class
   
   
   Class TestApplication
      
      Public Shared Sub Main()
         Try
            Dim bPointInRect As Bool = 0
            Dim myRect As New Rect()
            myRect.left = 10
            myRect.right = 100
            myRect.top = 10
            myRect.bottom = 100
            Dim myPoint As New Point()
            myPoint.x = 50
            myPoint.y = 50
            bPointInRect = NativeMethods.PtInRect(myRect, myPoint)
            If bPointInRect = Bool.True Then
               Console.WriteLine("Point lies within the Rect")
            Else
               Console.WriteLine("Point did not lie within the Rect")
            End If
         Catch e As Exception
            Console.WriteLine(("Exception : " + e.Message.ToString()))
         End Try
      End Sub 
   End Class

備註

這個列舉會搭配 使用 StructLayoutAttribute。 Common Language Runtime 預設會使用 Auto 版面配置值。 若要減少與 Auto 值相關聯的配置相關問題，C#、Visual Basic 和 C++ 編譯程式會指定 Sequential 實值類型的配置。

重要

欄位 StructLayoutAttribute.Pack 會控制數據欄位的對齊方式，因此不論您指定的值為何 LayoutKind ，都會影響版面配置。 根據預設，值為 Pack 0，表示目前平臺的預設封裝大小。 例如，當您使用 Explicit 版面配置值並在位元組界限上指定欄位對齊時，您必須設定 Pack 為 1 以取得所需的結果。