[Out, MarshalAs(UnmanagedType.Interface, IidParameterIndex = 2)] out IShellItem ppv);

        [Out][MarshalAs(UnmanagedType.Interface, IidParameterIndex = 2)] out IShellItem ppv);

         <MarshalAs(UnmanagedType.Interface, IidParameterIndex:=2)> ByRef ppv As IShellItem)

The type of the created COM object is usually an IShellItem instance; however, it does not have to be. (For example, you can ask for IShellItem2). To support different object types, change the type of the ppv parameter to match. Alternatively, specify a parameter of type object for ppv and perform the typecasting on return. The type of object returned in ppv will be the same as the type of interface given in the riid parameter.

        IShellItem oItem;

        SHCreateItemFromParsingName(path, IntPtr.Zero, typeof(IShellItem).GUID, out oItem);

    [Out, MarshalAs(UnmanagedType.Interface, IidParameterIndex = 3)] out IShellItem ppv);

    GPS_TEMPORARY = 0x00000004,   // A read/write store that only holds properties for the lifetime of the IShellItem object

Could someone delete IShellIten? It was a typo - meant to be IShellItem.

                   [In, MarshalAs ( UnmanagedType.Interface )] IShellItem psiFolder );

                [In, MarshalAs ( UnmanagedType.Interface )] IShellItem psi,

               [In, MarshalAs ( UnmanagedType.Interface )] IShellItem psi,

                   [In, MarshalAs ( UnmanagedType.Interface )] IShellItem psiFolder );

                [In, MarshalAs ( UnmanagedType.Interface )] IShellItem psi,

               [In, MarshalAs ( UnmanagedType.Interface )] IShellItem psi,

    void SetDefaultFolder ( [In, MarshalAs ( UnmanagedType.Interface )] IShellItem psi );

    void SetFolder ( [In, MarshalAs ( UnmanagedType.Interface )] IShellItem psi );

    void GetFolder ( [MarshalAs ( UnmanagedType.Interface )] out IShellItem ppsi );

    void GetCurrentSelection ( [MarshalAs ( UnmanagedType.Interface )] out IShellItem ppsi );

    void GetResult ( [MarshalAs ( UnmanagedType.Interface )] out IShellItem ppsi );

    void AddPlace ( [In, MarshalAs ( UnmanagedType.Interface )] IShellItem psi, NativeMethods.FDAP fdap );

    // Not supported:  IShellItemFilter is not defined, converting to IntPtr

    void GetResults ( [MarshalAs ( UnmanagedType.Interface )] out IShellItemArray ppenum );

    void GetSelectedItems ( [MarshalAs ( UnmanagedType.Interface )] out IShellItemArray ppsai );

    void SetDefaultFolder ( [In, MarshalAs ( UnmanagedType.Interface )] IShellItem psi );

    void SetFolder ( [In, MarshalAs ( UnmanagedType.Interface )] IShellItem psi );

    void GetFolder ( [MarshalAs ( UnmanagedType.Interface )] out IShellItem ppsi );

    void GetCurrentSelection ( [MarshalAs ( UnmanagedType.Interface )] out IShellItem ppsi );

    void GetResult ( [MarshalAs ( UnmanagedType.Interface )] out IShellItem ppsi );

    void AddPlace ( [In, MarshalAs ( UnmanagedType.Interface )] IShellItem psi, NativeMethods.FDAP fdap );

    // Not supported:  IShellItemFilter is not defined, converting to IntPtr

    void SetSaveAsItem ( [In, MarshalAs ( UnmanagedType.Interface )] IShellItem psi );

    void ApplyProperties ( [In, MarshalAs ( UnmanagedType.Interface )] IShellItem psi,

    public interface IShellItemImageFactory

    Public Interface IShellItemImageFactory    

To get a thumbnail for a shell item, simply cast the IShellItem instance to IShellItemImageFactory and call GetImage() on it. Usage may look something like this:

    IShellItem ppsi = null;

    // GUID of IShellItem.

    ((IShellItemImageFactory)ppsi).GetImage(new SIZE(256, 256), 0x0, out hbitmap);

interface IShellItemArray

    void GetItemAt ( [In] uint dwIndex, [MarshalAs ( UnmanagedType.Interface )] out IShellItem ppsi );

Public Interface IShellItemArray

    Function GetItemAt(<[In]()> dwIndex As UInteger, <MarshalAs(UnmanagedType.[Interface])> ByRef ppsi As IShellItem) As Integer

interface IShellItemFilter

     int IncludeItem([In, MarshalAs(UnmanagedType.Interface)] IShellItem psi);

     int GetEnumFlagsForItem([In, MarshalAs(UnmanagedType.Interface)] IShellItem psi, out SHCONTF pgrfFlags);

Interface IShellItemFilter

    public interface IShellItemImageFactory

    Public Interface IShellItemImageFactory    

To get a thumbnail for a shell item, simply cast the IShellItem instance to IShellItemImageFactory and call GetImage() on it. Usage may look something like this:

    IShellItem ppsi = null;

    // GUID of IShellItem.

    ((IShellItemImageFactory)ppsi).GetImage(new SIZE(256, 256), 0x0, out hbitmap);

This appears to be a typo. The name should be IShellItem

        [In] IShellItem pShellItem,

static extern int PSGetItemPropertyHandler(IShellItem punkItem, bool fReadWrite, ref Guid riid, out IPropertyStore ppv);

IShellItem, IPropertyStore

public static IPropertyStore GetPropertyStoreFromShellItem(IShellItem shellitem, bool fReadWrite)