This enumeration is used with System.Runtime.InteropServices.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, and C++ compilers specify Sequential layout for value types.
The StructLayoutAttribute.Pack field controls the alignment of data fields, and thus affects the layout regardless of the System.Runtime.InteropServices.LayoutKind value you specify. By default, the value of StructLayoutAttribute.Pack is 0, which indicates the default packing size for the current platform. For example, when you use the Explicit layout value and specify field alignments on byte boundaries, you must set StructLayoutAttribute.Pack to 1 to get the desired result.
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.
The precise position of each member of an object in unmanaged memory is explicitly controlled, subject to the setting of the StructLayoutAttribute.Pack field. Each member must use the System.Runtime.InteropServices.FieldOffsetAttribute to indicate the position of that field within the type.
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.