LayoutKind Enumeration
Controls the layout of an object when exported to unmanaged code.
[Visual Basic] <Serializable> Public Enum LayoutKind [C#] [Serializable] public enum LayoutKind [C++] [Serializable] __value public enum LayoutKind [JScript] public Serializable enum LayoutKind
Remarks
This enumeration is used with StructLayoutAttribute. The common language runtime uses the Auto layout value by default. To reduce layout-related problems associated with the Auto value, C#, Visual Basic .NET, and C++ compilers specify Sequential layout for value types.
Members
| Member name | Description |
|---|---|
| Auto Supported by the .NET Compact Framework. | The runtime automatically chooses an appropriate layout for the members of an object in unmanaged memory. Objects defined with this enumeration member cannot be exposed outside of managed code. Attempting to do so generates an exception. |
| Explicit Supported by the .NET Compact Framework. | The precise position of each member of an object in unmanaged memory is explicitly controlled. Each member must use the FieldOffsetAttribute to indicate the position of that field within the type. |
| Sequential Supported by the .NET Compact Framework. | The members of the object are laid out sequentially, in the order in which they appear when exported to unmanaged memory. The members are laid out according to the packing specified in StructLayoutAttribute.Pack, and can be noncontiguous. |
Example
[Visual Basic, C#, C++] 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.
[Visual Basic] Enum Bool [False] = 0 [True] End Enum 'Bool <StructLayout(LayoutKind.Sequential)> _ Public Structure Point Public x As Integer Public y As Integer End Structure 'Point <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 'Rect Class LibWrapper <DllImport("user32.dll", CallingConvention := CallingConvention.StdCall)> _ Public Shared Function PtInRect(ByRef r As Rect, p As Point) As Bool End Function End Class 'LibWrapper 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 = LibWrapper.PtInRect(myRect, myPoint) If bPointInRect = Bool.True Then Console.WriteLine("Point lies within the Rect") Else Console.WriteLine("Point did not lies within the Rect") End If Catch e As Exception Console.WriteLine(("Exception : " + e.Message.ToString())) End Try End Sub 'Main End Class 'TestApplication [C#] 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; } class LibWrapper { [DllImport("user32.dll", CallingConvention=CallingConvention.StdCall)] public 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 = LibWrapper.PtInRect(ref myRect, myPoint); if(bPointInRect == Bool.True) Console.WriteLine("Point lies within the Rect"); else Console.WriteLine("Point did not lies within the Rect"); } catch(Exception e) { Console.WriteLine("Exception : " + e.Message); } } } [C++] __value enum Bool { False = 0, True }; [StructLayout(LayoutKind::Sequential)] __value struct Point { public: int x; public: 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; }; __gc class LibWrapper { public: [DllImport(S"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 = LibWrapper::PtInRect(&myRect, myPoint); if (bPointInRect == Bool::True) Console::WriteLine(S"Point lies within the Rect"); else Console::WriteLine(S"Point did not lie within the Rect"); } catch (Exception* e) { Console::WriteLine(S"Exception : {0}", e->Message); } }
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Requirements
Namespace: System.Runtime.InteropServices
Platforms: Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 family, .NET Compact Framework
Assembly: Mscorlib (in Mscorlib.dll)