如何使用.NET提取FoxPro备忘录字段中的数据?

最终不得不自己做一些工作,但也许它可以帮助其他人在未来:

        public static object GetDbaseOrFoxproRawValue(string DBPath, string TableName, string ColumnName, 
        string CompareColumnName, string CompareValue, bool CompareColumnIsAutoKey)
    {
        using (BinaryReader read = new BinaryReader(File.Open(
            Path.Combine(DBPath, TableName + ".dbf"), FileMode.Open, FileAccess.Read, FileShare.ReadWrite)))
        {
            // Is it a type of file that I can handle?
            if (new byte[] { 0x02, 0x03, 0x30, 0x43, 0x63, 0x83, 0x8b,
                             0xcb, 0xf5, 0xfb }.Contains(read.ReadByte()))
            {
                // Skip date.
                read.BaseStream.Seek(3, SeekOrigin.Current);

                // Read useful datas...
                uint RecordCount = read.ReadUInt32();
                ushort FirstRecord = read.ReadUInt16();
                ushort RecordLength = read.ReadUInt16();
                int FieldCount = FirstRecord - 296 / 32;

                // Make sure things aren't stupid.
                ColumnName = ColumnName.ToLower();
                CompareColumnName = CompareColumnName.ToLower();

                // Find target column (field)
                string temp;
                UInt32 CompareFieldOffset = uint.MaxValue, FieldOffset = uint.MaxValue;
                byte CompareFieldLength = 0, FieldLength = 0;
                char FieldType = ' ';
                for (int i = 0; i < FieldCount; i++)
                {
                    read.BaseStream.Seek(32 + (i * 32), SeekOrigin.Begin);
                    temp = Encoding.ASCII.GetString(read.ReadBytes(11)).Replace("\0", "").ToLower();
                    if (temp == CompareColumnName)
                    {
                        read.ReadChar();
                        CompareFieldOffset = read.ReadUInt32();
                        CompareFieldLength = read.ReadByte();
                    }
                    if (temp == ColumnName)
                    {
                        FieldType = read.ReadChar();
                        FieldOffset = read.ReadUInt32();
                        FieldLength = read.ReadByte();
                    }

                    if (CompareFieldOffset != uint.MaxValue && FieldOffset != uint.MaxValue)
                        break;
                }

                // Make sure we can continue.
                if (CompareFieldOffset == uint.MaxValue || 
                    FieldOffset == uint.MaxValue) return null;

                // Iterate through each record to find the one we want.
                for (int index = 0; index < RecordCount; index++)
                {
                    read.BaseStream.Seek(FirstRecord + (index * RecordLength) + CompareFieldOffset, SeekOrigin.Begin);
                    temp = Encoding.Default.GetString(read.ReadBytes(CompareFieldLength)).Replace("\0", "");
                    if (temp == CompareValue)
                    {
                        read.BaseStream.Seek(FirstRecord + (index * RecordLength) + FieldOffset, SeekOrigin.Begin);
                        switch (FieldType)
                        {
                            case 'M':
                            case 'I': return read.ReadUInt32();
                            case 'C':
                            default: return Encoding.Default.GetString(read.ReadBytes(FieldLength)).Replace("\0", "");
                        }
                    }
                }
            }
            else
            {
                return null;
            }
        }

        return null;
    }

只需从中获取结果,并将其用作备忘录文件的索引(该代码使用msdn文档非常简单)。

我对C或FoxPro或SQL Server不太熟悉,因此在这方面我不能给您太多建议。

但是,如果找不到合适的驱动程序,可以考虑自己分析原始数据和备忘录文件。另一个问题是:

What's the easiest way to read a FoxPro DBF file from Python?

信不信由你,如果你决定编写自己的C解析器,这些文件格式很容易解析。这些规范可从Microsoft获得:

• Visual FoxPro File Structures
• Table File Structure
• Memo File Structure

我使用ODBC链接vfp 8表,而memo字段工作正常。我不知道OLEDB是否不同。

这里可能没有Visual FoxPro表。许多VFP系统使用与它们所替换的FoxPro 2或DBase应用程序相同的表。您可以查看文件头,也可以尝试其他一个ODBC驱动程序,看看它们是否工作。