using System.Runtime.InteropServices;   //操作Dll的類空間   
  
 class CGicomIndex  
    {  
        [DllImport("Index_dll.dll")]  
        unsafe private static extern Int32 create_index_file(IntPtr filename, IntPtr fieldname, UInt32 tongshu, IntPtr err);  
        //VC原型　create_index_file( char*filename, char * fieldname, unsigned long tongshu, char *err);  
 
        #region " bool CreateIndexFile( string m_strFileName, string m_strFieldName, UInt32 m_key, ref string strErr ) 對DBF文件按照指定的字段創建索引"   
        /// <summary>   
        /// 對DBF文件按照指定的字段創建索引   
        /// </summary>   
        /// <param name="m_strFileName">DBF文件路徑</param>   
        /// <param name="m_strFieldName">創建索引的字段名稱</param>   
        /// <param name="m_key">索引桶數(文件記錄的最大數)</param>   
        /// <param name="strErr">出錯信息</param>   
        /// <returns>成功 true</returns>   
        public static bool CreateIndexFile( string m_strFileName, string m_strFieldName, UInt32 m_key, ref string strErr )  
        {  
            try  
            {  
                IntPtr ptrFileName, ptrFieldName, ptrErr;  
  
                //根據數據的長度申請非托管空間   
                ptrFileName = mallocIntptr(m_strFileName);  
                ptrFieldName = mallocIntptr(m_strFieldName);  
                ptrErr = mallocIntptr(300);  
  
                //創建索引   
                if (create_index_file(ptrFileName, ptrFieldName, m_key, ptrErr) != 1)  
                {  
                    strErr = Marshal.PtrToStringAnsi(ptrErr);  
                    Marshal.FreeHGlobal(ptrFileName);  
                    Marshal.FreeHGlobal(ptrFieldName);  
                    Marshal.FreeHGlobal(ptrErr);  
                    return false;  
                }  
                Marshal.FreeHGlobal(ptrFileName);  
                Marshal.FreeHGlobal(ptrFieldName);  
                Marshal.FreeHGlobal(ptrErr);  
                return true;  
            }  
            catch (System.Exception ex)  
            {  
                strErr = ex.Message;  
                return false;  
            }  
        }  
        #endregion  
 
        #region " IntPtr mallocIntptr( string strData ) 根據數據的長度申請非托管空間"   
        /// <summary>   
        /// 根據數據的長度申請非托管空間   
        /// </summary>   
        /// <param name="strData">要申請非托管空間的數據</param>   
        /// <returns>指向非拖管空間的指針</returns>   
        private static IntPtr mallocIntptr( string strData )  
        {  
            //先將字符串轉化成字節方式   
            Byte[] btData = System.Text.Encoding.Default.GetBytes(strData);  
  
            //申請非拖管空間   
            IntPtr m_ptr = Marshal.AllocHGlobal(btData.Length);  
  
            //給非拖管空間清０    
            Byte[] btZero = new Byte[btData .Length+ 1]; //一定要加1,否則后面是亂碼，原因未找到   
            Marshal.Copy(btZero, 0, m_ptr, btZero.Length);  
  
            //給指針指向的空間賦值   
            Marshal.Copy(btData, 0, m_ptr, btData.Length);  
  
            return m_ptr;  
        }  
  
        /// <summary>   
        /// 根據長度申請非托管空間   
        /// </summary>   
        /// <param name="strData">要申請非托管空間的大小</param>   
        /// <returns>指向非拖管空間的指針</returns>   
        private static IntPtr mallocIntptr( int length )  
        {  
            //申請非拖管空間   
            IntPtr m_ptr = Marshal.AllocHGlobal(length);  
  
            //給非拖管空間清０    
            Byte[] btZero = new Byte[length + 1]; //一定要加1,否則后面是亂碼，原因未找到   
            Marshal.Copy(btZero, 0, m_ptr, btZero.Length);  
  
            //給指針指向的空間賦值   
            Marshal.Copy(btZero, 0, m_ptr, length);  
  
            return m_ptr;  
        }  
        #endregion   
    }