Memory alignment for structure variables for p / invoke - lines lose the last character

I am trying to read records from the Btrieve database (v6.15) using the btrieve API from C # code through P / Invoke.

I was able to read the records, however the last character of the lines is truncated while reading. If I increase the row size in my data structure, then the row will be read correctly, but this time the next variable will not be read correctly.

What could be wrong here?

Declaring a Btrieve Function:

        [DllImport("WBTRV32.dll", CharSet = CharSet.Ansi)]
    static extern short BTRCALL(ushort operation,
        [MarshalAs(UnmanagedType.LPArray, SizeConst = 128)] byte[] posBlk,
        [MarshalAs(UnmanagedType.Struct, SizeConst = 255)] 
        ref RecordBuffer databuffer, 
        ref int dataLength, 
        [MarshalAs(UnmanagedType.LPArray, SizeConst = 255)] char[] keyBffer, 
        ushort keyLength, ushort keyNum);

Definition of my structure:

    [StructLayout(LayoutKind.Sequential, Pack = 1, CharSet = CharSet.Ansi)]
    public struct RecordBuffer
    {
        public short docType;
        [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 15)]
        public string docDescPlural;
        public short sorting;
        [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 15)]
        public string docDescSingle;
        public short copyOtherThanSrc;
        public double defaultNotebookNo;
    }

These are the sizes for the columns from the Btreive database manager:

• signed int, 2 bytes
• string, 15 bytes
• signed int, 2 bytes
• string, 15 bytes
• signed int, 2 bytes
• float, 8 bytes

The code:

    private void PopulateAllRecords(string fileName)
    {
        byte[] positionBlock = new byte[128];
        char[] fileNameArray = fileName.ToCharArray();

        // Open file
        RecordBuffer dataBuffer = new RecordBuffer();
        int bufferLength = System.Runtime.InteropServices.Marshal.SizeOf(dataBuffer);
        BReturnCodes status = (BReturnCodes) BTRCALL(
            BOPEN, positionBlock, ref dataBuffer, ref bufferLength, fileNameArray, 0, 0);

        if (status == BReturnCodes.NO_ERROR)
        {
            // Get first record
            dataBuffer = new RecordBuffer();
            status = (BReturnCodes) BTRCALL(
                BGETFIRST, positionBlock, ref dataBuffer, ref bufferLength, fileNameArray, 0, 0);

            if (status == BReturnCodes.NO_ERROR)
            {
                AddListViewItem(dataBuffer);
            }

            // Get subsequent records
            while (status == BReturnCodes.NO_ERROR) // BReturnCodes.END_OF_FILE or an error will occur
            {
                dataBuffer = new RecordBuffer();
                status = (BReturnCodes)BTRCALL(
                    BGETNEXT, positionBlock, ref dataBuffer, ref bufferLength, fileNameArray, 0, 0);

                if (status == BReturnCodes.NO_ERROR)
                {
                    AddListViewItem(dataBuffer);                        
                }
            }
        }
        else
        {
            MessageBox.Show("Error occured while opening file: " + status.ToString());
        }
    }

    private void AddListViewItem(RecordBuffer buffer)
    {
        ListViewItem item = new ListViewItem(buffer.docType.ToString());
        item.SubItems.Add(buffer.docDescPlural);
        item.SubItems.Add(buffer.sorting.ToString());
        item.SubItems.Add(buffer.docDescSingle);
        item.SubItems.Add(buffer.copyOtherThanSrc.ToString());
        item.SubItems.Add(buffer.defaultNotebookNo.ToString());
        listView.Items.Add(item);
    }

Edit: changing a string in a char array (thanks to a response to weismat) resolved the problem. Happy!

    [StructLayout(LayoutKind.Sequential, Pack = 1, CharSet = CharSet.Ansi)]
    public struct RecordBuffer
    {
        public short docType;
        [MarshalAs(UnmanagedType.ByValArray, SizeConst = 15)]
        public char[] docDescPlural;
        public short sorting;
        [MarshalAs(UnmanagedType.ByValArray, SizeConst = 15)]
        public char[] docDescSingle;
        public short copyOtherThanSrc;
        public double defaultNotebookNo;
    }