StructLayoutAttribute Class

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

System.Object
  System.Attribute
    System.Runtime.InteropServices.StructLayoutAttribute

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

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

The StructLayoutAttribute type exposes the following members.

  NameDescription
Public methodStructLayoutAttribute(Int16)Initalizes a new instance of the StructLayoutAttribute class with the specified System.Runtime.InteropServices.LayoutKind enumeration member.
Public methodSupported by the XNA FrameworkSupported by Portable Class LibrarySupported in .NET for Windows Store appsStructLayoutAttribute(LayoutKind)Initalizes a new instance of the StructLayoutAttribute class with the specified System.Runtime.InteropServices.LayoutKind enumeration member.
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  NameDescription
Public propertyTypeIdWhen implemented in a derived class, gets a unique identifier for this Attribute. (Inherited from Attribute.)
Public propertySupported by Portable Class LibrarySupported in .NET for Windows Store appsValueGets the LayoutKind value that specifies how the class or structure is arranged.
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  NameDescription
Public methodSupported by the XNA FrameworkSupported by Portable Class LibrarySupported in .NET for Windows Store appsEqualsInfrastructure. Returns a value that indicates whether this instance is equal to a specified object. (Inherited from Attribute.)
Public methodSupported by the XNA FrameworkSupported by Portable Class LibrarySupported in .NET for Windows Store appsGetHashCodeReturns the hash code for this instance. (Inherited from Attribute.)
Public methodSupported by the XNA FrameworkSupported by Portable Class LibrarySupported in .NET for Windows Store appsGetTypeGets the Type of the current instance. (Inherited from Object.)
Public methodIsDefaultAttributeWhen overridden in a derived class, indicates whether the value of this instance is the default value for the derived class. (Inherited from Attribute.)
Public methodSupported by the XNA FrameworkMatchWhen overridden in a derived class, returns a value that indicates whether this instance equals a specified object. (Inherited from Attribute.)
Public methodSupported by the XNA FrameworkSupported by Portable Class LibrarySupported in .NET for Windows Store appsToStringReturns a string that represents the current object. (Inherited from Object.)
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  NameDescription
Public fieldSupported by the XNA FrameworkSupported by Portable Class LibrarySupported in .NET for Windows Store appsCharSetIndicates whether string data fields within the class should be marshaled as LPWSTR or LPSTR by default.
Public fieldSupported by Portable Class LibrarySupported in .NET for Windows Store appsPackControls the alignment of data fields of a class or structure in memory.
Public fieldSupported by the XNA FrameworkSupported by Portable Class LibrarySupported in .NET for Windows Store appsSizeIndicates the absolute size of the class or structure.
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  NameDescription
Explicit interface implemetationPrivate method_Attribute.GetIDsOfNamesMaps a set of names to a corresponding set of dispatch identifiers. (Inherited from Attribute.)
Explicit interface implemetationPrivate method_Attribute.GetTypeInfoRetrieves the type information for an object, which can be used to get the type information for an interface. (Inherited from Attribute.)
Explicit interface implemetationPrivate method_Attribute.GetTypeInfoCountRetrieves the number of type information interfaces that an object provides (either 0 or 1). (Inherited from Attribute.)
Explicit interface implemetationPrivate method_Attribute.InvokeProvides access to properties and methods exposed by an object. (Inherited from Attribute.)
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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 blittable types, 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
   {
      [DllImport("kernel32.dll")]
      public static extern void GetSystemTime([MarshalAs(UnmanagedType.LPStruct)]MySystemTime st);
   };

   class TestApplication
   {      
      public static void Main()
      {
         try
         {
            MySystemTime sysTime = new MySystemTime();
            LibWrapper.GetSystemTime(sysTime);
            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);
         }
      }
   }
}

.NET Framework

Supported in: 4.5, 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Portable Class Library

Supported in: Portable Class Library

.NET for Windows Store apps

Supported in: Windows 8

.NET for Windows Phone apps

Supported in: Windows Phone 8.1, Windows Phone Silverlight 8.1, Windows Phone Silverlight 8

Windows Phone 8.1, Windows Phone 8, Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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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