C# Definition:

struct STAT_CHUNK {
        /// <summary>
        /// The chunk identifier. Chunk identifiers must be unique for the
        /// current instance of the IFilter interface.
        /// Chunk identifiers must be in ascending order. The order in which
        /// chunks are numbered should correspond to the order in which they appear
        /// in the source document. Some search engines can take advantage of the
        /// proximity of chunks of various properties. If so, the order in which
        /// chunks with different properties are emitted will be important to the
        /// search engine.
        /// </summary>
        public int idChunk;

        /// <summary>
        /// The type of break that separates the previous chunk from the current
        ///  chunk. Values are from the CHUNK_BREAKTYPE enumeration.
        /// </summary>
        [MarshalAs(UnmanagedType.U4)]
        public CHUNK_BREAKTYPE breakType;

        /// <summary>
        /// Flags indicate whether this chunk contains a text-type or a
        /// value-type property.
        /// Flag values are taken from the CHUNKSTATE enumeration. If the CHUNK_TEXT flag is set,
        /// IFilter::GetText should be used to retrieve the contents of the chunk
        /// as a series of words.
        /// If the CHUNK_VALUE flag is set, IFilter::GetValue should be used to retrieve
        /// the value and treat it as a single property value. If the filter dictates that the same
        /// content be treated as both text and as a value, the chunk should be emitted twice in two
        /// different chunks, each with one flag set.
        /// </summary>
        [MarshalAs(UnmanagedType.U4)]
        public CHUNKSTATE flags;

        /// <summary>
        /// The language and sublanguage associated with a chunk of text. Chunk locale is used
        /// by document indexers to perform proper word breaking of text. If the chunk is
        /// neither text-type nor a value-type with data type VT_LPWSTR, VT_LPSTR or VT_BSTR,
        /// this field is ignored.
        /// </summary>
        public int locale;

        /// <summary>
        /// The property to be applied to the chunk. If a filter requires that       the same text
        /// have more than one property, it needs to emit the text once for each       property
        /// in separate chunks.
        /// </summary>
        public FULLPROPSPEC attribute;

        /// <summary>
        /// The ID of the source of a chunk. The value of the idChunkSource     member depends on the nature of the chunk:
        /// If the chunk is a text-type property, the value of the idChunkSource       member must be the same as the value of the idChunk member.
        /// If the chunk is an public value-type property derived from textual       content, the value of the idChunkSource member is the chunk ID for the
        /// text-type chunk from which it is derived.
        /// If the filter attributes specify to return only public value-type
        /// properties, there is no content chunk from which to derive the current
        /// public value-type property. In this case, the value of the
        /// idChunkSource member must be set to zero, which is an invalid chunk.
        /// </summary>
        public int idChunkSource;

        /// <summary>
        /// The offset from which the source text for a derived chunk starts in
        /// the source chunk.
        /// </summary>
        public int cwcStartSource;

        /// <summary>
        /// The length in characters of the source text from which the current
        /// chunk was derived.
        /// A zero value signifies character-by-character correspondence between
        /// the source text and
        /// the derived text. A nonzero value means that no such direct
        /// correspondence exists
        /// </summary>
        public int cwcLenSource;
}

VB Definition:

#Region "STAT_CHUNK Structure Definition"

    <StructLayout(LayoutKind.Sequential)> _
    Public Structure STAT_CHUNK
     Public idChunk As Integer
     <MarshalAs(UnmanagedType.U4)> _
        Public breakType As CHUNK_BREAKTYPE
     <MarshalAs(UnmanagedType.U4)> _
        Public flags As CHUNKSTATE
     Public locale As Integer
     Public attribute As FULLPROPSPEC
     Public idChunkSource As Integer
     Public cwcStartSource As Integer
     Public cwcLenSource As Integer
    Public idChunk As Integer
       <MarshalAs(UnmanagedType.U4)> Public breakType As CHUNK_BREAKTYPE
       <MarshalAs(UnmanagedType.U4)> Public flags As CHUNKSTATE
    Public locale As Integer
    Public attribute As FULLPROPSPEC
    Public idChunkSource As Integer
    Public cwcStartSource As Integer
    Public cwcLenSource As Integer
    End Structure