LayoutKind 列舉

定義

控制匯出至 Unmanaged 程式碼時的物件配置。Controls the layout of an object when exported to unmanaged code.

public enum class LayoutKind
[System.Runtime.InteropServices.ComVisible(true)]
[System.Serializable]
public enum LayoutKind
type LayoutKind = 
Public Enum LayoutKind
繼承
LayoutKind
屬性

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。The runtime automatically chooses an appropriate layout for the members of an object in unmanaged memory. 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。Objects defined with this enumeration member cannot be exposed outside of managed code. 嘗試這麼做會產生例外狀況。Attempting to do so generates an exception.

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)。The precise position of each member of an object in unmanaged memory is explicitly controlled, subject to the setting of the Pack field. 每個成員必須使用 FieldOffsetAttribute,表示該欄位在型別中的位置。Each member must use the FieldOffsetAttribute to indicate the position of that field within the type.

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。The members of the object are laid out sequentially, in the order in which they appear when exported to unmanaged memory. 成員是根據 Pack 中所指定的封裝來配置。The members are laid out according to the packing specified in Pack, and can be noncontiguous.

範例

下列範例顯示 PtInRect 函式的 managed 宣告,此宣告會檢查某個點是否位於矩形內,並以順序配置和 Rect 結構定義具有明確配置的 Point 結構。The following example shows the managed declaration of the PtInRect function, which checks whether a point lies within a rectangle, and defines a Point structure with Sequential layout and a Rect structure with Explicit layout.

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

此列舉會與 StructLayoutAttribute搭配使用。This enumeration is used with StructLayoutAttribute. 通用語言執行時間預設會使用 Auto 的版面配置值。The common language runtime uses the Auto layout value by default. 若要減少與 Auto 值相關聯的配置相關問題C#,Visual Basic 和C++編譯器會指定實數值型別的 Sequential 配置。To reduce layout-related problems associated with the Auto value, C#, Visual Basic, and C++ compilers specify Sequential layout for value types.

重要

[StructLayoutAttribute.Pack] 欄位會控制資料欄位的對齊,因此不論您指定的 LayoutKind 值為何,都會影響配置。The StructLayoutAttribute.Pack field controls the alignment of data fields, and thus affects the layout regardless of the LayoutKind value you specify. 根據預設,Pack 的值為0,表示目前平臺的預設封裝大小。By default, the value of Pack is 0, which indicates the default packing size for the current platform. 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方式時,您必須將 Pack 設定為1,以取得所需的結果。For example, when you use the Explicit layout value and specify field alignments on byte boundaries, you must set Pack to 1 to get the desired result.

適用於