StructLayoutAttribute Class


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Lets you control the physical layout of the data fields of a class or structure in memory.

Namespace:   System.Runtime.InteropServices
Assembly:  mscorlib (in mscorlib.dll)


[AttributeUsageAttribute(AttributeTargets.Class | AttributeTargets.Struct, 
	Inherited = false)]
public sealed class StructLayoutAttribute : Attribute


Initalizes a new instance of the StructLayoutAttribute class with the specified System.Runtime.InteropServices.LayoutKind enumeration member.


Initalizes a new instance of the StructLayoutAttribute class with the specified System.Runtime.InteropServices.LayoutKind enumeration member.


When implemented in a derived class, gets a unique identifier for this Attribute.(Inherited from Attribute.)


Gets the LayoutKind value that specifies how the class or structure is arranged.


This API supports the product infrastructure and is not intended to be used directly from your code. Returns a value that indicates whether this instance is equal to a specified object.(Inherited from Attribute.)


Returns the hash code for this instance.(Inherited from Attribute.)


Gets the Type of the current instance.(Inherited from Object.)


When overridden in a derived class, indicates whether the value of this instance is the default value for the derived class.(Inherited from Attribute.)


When overridden in a derived class, returns a value that indicates whether this instance equals a specified object.(Inherited from Attribute.)


Returns a string that represents the current object.(Inherited from Object.)


Indicates whether string data fields within the class should be marshaled as LPWSTR or LPSTR by default.


Controls the alignment of data fields of a class or structure in memory.


Indicates the absolute size of the class or structure.

System_CAPS_pubinterfaceSystem_CAPS_privmethod_Attribute.GetIDsOfNames(Guid, IntPtr, UInt32, UInt32, IntPtr)

Maps a set of names to a corresponding set of dispatch identifiers.(Inherited from Attribute.)

System_CAPS_pubinterfaceSystem_CAPS_privmethod_Attribute.GetTypeInfo(UInt32, UInt32, IntPtr)

Retrieves the type information for an object, which can be used to get the type information for an interface.(Inherited from Attribute.)


Retrieves the number of type information interfaces that an object provides (either 0 or 1).(Inherited from Attribute.)

System_CAPS_pubinterfaceSystem_CAPS_privmethod_Attribute.Invoke(UInt32, Guid, UInt32, Int16, IntPtr, IntPtr, IntPtr, IntPtr)

Provides access to properties and methods exposed by an object.(Inherited from Attribute.)

You can apply this attribute to classes or structures.

The common language runtime controls the physical layout of the data fields of a class or structure in managed memory. However, if you want to pass the type to unmanaged code, you can use the StructLayoutAttribute attribute to control the unmanaged layout of the type. Use the attribute with LayoutKind.Sequential to force the members to be laid out sequentially in the order they appear. For , LayoutKind.Sequential controls both the layout in managed memory and the layout in unmanaged memory. For non-blittable types, it controls the layout when the class or structure is marshaled to unmanaged code, but does not control the layout in managed memory. Use the attribute with LayoutKind.Explicit to control the precise position of each data member. This affects both managed and unmanaged layout, for both blittable and non-blittable types. Using LayoutKind.Explicit requires that you use the FieldOffsetAttribute attribute to indicate the position of each field within the type.

C#, Visual Basic, and C++ compilers apply the Sequential layout value to structures by default. For classes, you must apply the LayoutKind.Sequential value explicitly. The Tlbimp.exe (Type Library Importer) also applies the StructLayoutAttribute attribute; it always applies the LayoutKind.Sequential value when it imports a type library.

The following example demonstrates a managed declaration of the GetSystemTime function and defines MySystemTime class with LayoutKind.Explicit layout. GetSystemTime gets the system time and prints to the console.

using System;
using System.Runtime.InteropServices;

namespace InteropSample

   [StructLayout(LayoutKind.Explicit, Size=16, CharSet=CharSet.Ansi)]
   public class MySystemTime 
      [FieldOffset(0)]public ushort wYear; 
      [FieldOffset(2)]public ushort wMonth;
      [FieldOffset(4)]public ushort wDayOfWeek; 
      [FieldOffset(6)]public ushort wDay; 
      [FieldOffset(8)]public ushort wHour; 
      [FieldOffset(10)]public ushort wMinute; 
      [FieldOffset(12)]public ushort wSecond; 
      [FieldOffset(14)]public ushort wMilliseconds; 

   class LibWrapper
      public static extern void GetSystemTime([MarshalAs(UnmanagedType.LPStruct)]MySystemTime st);

   class TestApplication
      public static void Main()
            MySystemTime sysTime = new MySystemTime();
            Console.WriteLine("The System time is {0}/{1}/{2} {3}:{4}:{5}", sysTime.wDay,
               sysTime.wMonth, sysTime.wYear, sysTime.wHour, sysTime.wMinute, sysTime.wSecond);            
         catch(TypeLoadException e)
            Console.WriteLine("TypeLoadException : " + e.Message);
         catch(Exception e)
            Console.WriteLine("Exception : " + e.Message);

Universal Windows Platform
Available since 8
.NET Framework
Available since 1.1
Portable Class Library
Supported in: portable .NET platforms
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1

Any public static ( Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

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