Marshal.OffsetOf Method (Type, String)


The .NET API Reference documentation has a new home. Visit the .NET API Browser on to see the new experience.

Returns the field offset of the unmanaged form of the managed class.

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

public static IntPtr OffsetOf(
	Type t,
	string fieldName


Type: System.Type

A value type or formatted reference type that specifies the managed class. You must apply the StructLayoutAttribute to the class.

Type: System.String

The field within the t parameter.

Return Value

Type: System.IntPtr

The offset, in bytes, for the fieldName parameter within the specified class that is declared by platform invoke.

Exception Condition

The class cannot be exported as a structure or the field is nonpublic. Beginning with the .NET Framework version 2.0, the field may be private.


The t parameter is null.

OffsetOf provides the offset in terms of the unmanaged structure layout, which does not necessarily correspond to the offset of the managed structure layout. Marshaling the structure can transform the layout and alter the offset. The t parameter can be a value type or a formatted reference type (with either a sequential or explicit layout). You can obtain the size of the entire layout by using the Marshal.SizeOf method. For additional information, see Default Marshaling for Value Types.


Beginning with the .NET Framework version 2.0, OffsetOf may expose private fields.

Universal Windows Platform
Available since 8
.NET Framework
Available since 1.1
Portable Class Library
Supported in: portable .NET platforms
Windows Phone
Available since 8.1
Return to top