Type.IsLayoutSequential Property


Gets a value indicating whether the fields of the current type are laid out sequentially, in the order that they were defined or emitted to the metadata.

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

Public ReadOnly Property IsLayoutSequential As Boolean

Property Value

Type: System.Boolean

true if the Attributes property of the current type includes TypeAttributes.SequentialLayout; otherwise, false.

This property is provided as a convenience. Alternatively, you can use the TypeAttributes.LayoutMaskenumeration value to select the type layout attributes, and then test whether TypeAttributes.SequentialLayout is set. The TypeAttributes.AutoLayout, TypeAttributes.ExplicitLayout, and TypeAttributes.SequentialLayout enumeration values indicate the way the fields of the type are laid out in memory.

For dynamic types, you can specify TypeAttributes.SequentialLayout when you create the type. In code, apply the StructLayoutAttribute attribute with the LayoutKind.Sequential enumeration value to the type, to specify that layout is sequential.


You cannot use the GetCustomAttributes method to determine whether the StructLayoutAttribute has been applied to a type.

For more information, see section 9.1.2 of the specification for the Common Language Infrastructure (CLI) documentation, "Partition II: Metadata Definition and Semantics". The documentation is available online; see ECMA C# and Common Language Infrastructure Standards on MSDN and Standard ECMA-335 - Common Language Infrastructure (CLI) on the Ecma International Web site.

If the current Type represents a constructed generic type, this property applies to the generic type definition from which the type was constructed. For example, if the current Type represents MyGenericType<int> (MyGenericType(Of Integer) in Visual Basic), the value of this property is determined by MyGenericType<T>.

If the current Type represents a type parameter in the definition of a generic type or generic method, this property always returns false.

The following example creates an instance of a class for which the LayoutKind.Sequentialenumeration value in the StructLayoutAttribute class has been set, checks for the IsLayoutSequential property, and displays the result.

Imports System
Imports System.Reflection
Imports System.ComponentModel
Imports System.Runtime.InteropServices
Imports Microsoft.VisualBasic
Class MyTypeSequential1
End Class 'MyTypeSequential1
<StructLayoutAttribute(LayoutKind.Sequential)> Class MyTypeSequential2
    Public Shared Sub Main()
            ' Create an instance of MyTypeSequential1.
            Dim myObj1 As New MyTypeSequential1()
            Dim myTypeObj1 As Type = myObj1.GetType()
            ' Check for and display the SequentialLayout attribute.
            Console.WriteLine(ControlChars.Cr + "The object myObj1 has IsLayoutSequential: {0}.", myObj1.GetType().IsLayoutSequential.ToString())
            ' Create an instance of MyTypeSequential2.
            Dim myObj2 As New MyTypeSequential2()
            Dim myTypeObj2 As Type = myObj2.GetType()
            ' Check for and display the SequentialLayout attribute.
            Console.WriteLine(ControlChars.Cr + "The object myObj2 has IsLayoutSequential: {0}.", myObj2.GetType().IsLayoutSequential.ToString())
        Catch e As Exception
            Console.WriteLine(ControlChars.Cr + "An exception occurred: {0}", e.Message.ToString())
        End Try
    End Sub 'Main
End Class 'MyTypeSeq2

.NET Framework
Available since 1.1
Windows Phone Silverlight
Available since 8.0
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