.Net的數據庫天然支持MSSQLServer，但是並非其他數據庫不支持，而是微軟基於自身利益需要，在支持、營銷上推自己的數據庫產品;但是作為平台戰略，他並非排斥其他數據庫，而是參考Java體系提出了一套數據庫訪問規范，讓各個第三方進行開發，提供特定的驅動。
MySQL是免費的數據庫，在成本上具有無可替代的優勢，但是目前來講，並沒有提供。微軟把MySQL當作ODBC數據庫，可以按照ODBC.Net規范進行訪問，具體參考
http://www.microsoft.com/china/community/Columns/Luyan/6.mspx
而實際上，針對ODBC。Net的需要配置DSN的麻煩，而是出現了一個開源的系統MySQLDriverCS，對MySQL的開發進行了封裝，實現了.Net環境下對於MySQL數據庫系統的訪問。
http://sourceforge.Net/projects/MySQLdrivercs/
通過閱讀源代碼，我們看到MySQLDriverCS的思路是利用C函數的底層庫來操縱數據庫的，通常提供對MySQL數據庫的訪問的數據庫的C DLL是名為libmySQL.dll的驅動文件，MySQLDriverCS作為一個.Net庫進行封裝C風格的驅動。
具體如何進行呢?
打開工程後，我們看到其中有一個比較特殊的.cs文件CPrototypes.cs：
以下是引用片段：
#region LICENSE
/*
MySQLDriverCS: An C# driver for MySQL.
Copyright (c) 2002 Manuel Lucas Vi馻s Livschitz.
This file is part of MySQLDriverCS.
MySQLDriverCS is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
MySQLDriverCS is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implIEd warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with MySQLDriverCS; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#endregion
using System;
using System.Data;
using System.Runtime.InteropServices;
namespace MySQLDriverCS
{
//[StructLayout(LayoutKind.Sequential)]
public class MySQL_FIELD_FACTORY
{
static string version;
public static IMySQL_FIELD GetInstance()
{
if (version==null)
{
version = CPrototypes.GetClIEntInfo();
}
if (version.CompareTo("4.1.2-alpha")>=0)
{
return new MySQL_FIELD_VERSION_5();
}
else
return new MySQL_FIELD_VERSION_3();
}
}
public interface IMySQL_FIELD
{
string Name{get;}
uint Type{get;}
long Max_Length {get;}
}
///<summary>
/// FIEld descriptor
///</summary>
[StructLayout(LayoutKind.Sequential)]//"3.23.32", 4.0.1-alpha
internal class MYSQL_FIELD_VERSION_3: IMySQL_FIELD
{
///<summary>
/// Name of column
///</summary>
public string name;
///<summary>
/// Table of column if column was a fIEld
///</summary>
public string table;
//public string org_table; /* Org table name if table was an alias */
//public string db; /* Database for table */
///<summary>
/// def
///</summary>
public string def;
///<summary>
/// length
///</summary>
public long length;
///<summary>
/// max_length
///</summary>
public long max_length;
///<summary>
/// Div flags
///</summary>
public uint flags;
///<summary>
/// Number of decimals in fIEld
///</summary>
public uint decimals;
///<summary>
/// Type of fIEld. Se MySQL_com.h for types
///</summary>
public uint type;
///<summary>
/// Name
///</summary>
public string Name
{
get{return name;}
}
///<summary>
/// Type
///</summary>
public uint Type
{
get{return type;}
}
///<summary>
/// Max_Length
///</summary>
public long Max_Length
{
get {return max_length;}
}
}
///<summary>
/// FIEld descriptor
///</summary>
[StructLayout(LayoutKind.Sequential)]
internal class MYSQL_FIELD_VERSION_5: IMySQL_FIELD
{
///<summary>
/// Name of column
///</summary>
public string name;
///<summary>
/// Original column name, if an alias
///</summary>
public string org_name;
///<summary>
/// Table of column if column was a fIEld
///</summary>
public string table;
///<summary>
/// Org table name if table was an alias
///</summary>
public string org_table;
///<summary>
/// Database for table
///</summary>
public string db;
///<summary>
/// Catalog for table
///</summary>
//public string catalog;
///<summary>
/// def
///</summary>
public string def;
///<summary>
/// length
///</summary>
public long length;
///<summary>
/// max_length
///</summary>
public long max_length;
///<summary>
/// name_length
///</summary>
//public uint name_length;
///<summary>
/// org_name_length
///</summary>
public uint org_name_length;
///<summary>
/// table_length
///</summary>
public uint table_length;
///<summary>
/// org_table_length
///</summary>
public uint org_table_length;
///<summary>
/// db_length
///</summary>
public uint db_length;
///<summary>
/// catalog_length
///</summary>
public uint catalog_length;
///<summary>
/// def_length
///</summary>
public uint def_length;
///<summary>
/// Div flags
///</summary>
public uint flags;
///<summary>
/// Number of decimals in fIEld
///</summary>
public uint decimals;
///<summary>
/// Character set
///</summary>
public uint charsetnr;
///<summary>
/// Type of fIEld. Se MySQL_com.h for types
///</summary>
public uint type;
///<summary>
/// Name
///</summary>
public string Name
{
get {return name;}
}
///<summary>
/// Type
///</summary>
public uint Type
{
get {return type;}
}
///<summary>
/// Max_Length
///</summary>
public long Max_Length
{
get {return max_length;}
}
}
//[StructLayout(LayoutKind.Explicit)]
public enum enum_fIEld_types
{
FIELD_TYPE_DECIMAL, FIELD_TYPE_TINY,
FIELD_TYPE_SHORT, FIELD_TYPE_LONG,
FIELD_TYPE_FLOAT, FIELD_TYPE_DOUBLE,
FIELD_TYPE_NULL, FIELD_TYPE_TIMESTAMP,
FIELD_TYPE_LONGLONG,FIELD_TYPE_INT24,
FIELD_TYPE_DATE, FIELD_TYPE_TIME,
FIELD_TYPE_DATETIME, FIELD_TYPE_YEAR,
FIELD_TYPE_NEWDATE,
FIELD_TYPE_ENUM=247,
FIELD_TYPE_SET=248,
FIELD_TYPE_TINY_BLOB=249,
FIELD_TYPE_MEDIUM_BLOB=250,
FIELD_TYPE_LONG_BLOB=251,
FIELD_TYPE_BLOB=252,
FIELD_TYPE_VAR_STRING=253,
FIELD_TYPE_STRING=254,
FIELD_TYPE_GEOMETRY=255
};
///<summary>
/// C prototypes warpper for MySQLlib.
///</summary>
internal class CPrototypes
{
[ DllImport( "libmySQL.dll", EntryPoint="MySQL_init" )]
unsafe public static extern void* MySQL_init(void* must_be_null);
[ DllImport( "libmySQL.dll", EntryPoint="MySQL_close" )]
unsafe public static extern void MySQL_close(void* handle);
// BEGIN ADDITION 2004-07-01 BY Alex Seewald
// Enables us to call MySQL_option to activate compression and timeout
[ DllImport( "libmySQL.dll", EntryPoint="MySQL_options" )]
unsafe public static extern void mysql_options(void* MySQL, uint option, uint *value);
// END ADDITION 2004-07-01 By Alex Seewald
[ DllImport( "libmySQL.dll", EntryPoint="MySQL_real_connect" )]
unsafe public static extern void* mysql_real_connect(void* MySQL, string host, string user, string passwd, string db, uint port, string unix_socket, int clIEnt_flag);
[ DllImport( "libmySQL.dll", EntryPoint="MySQL_query" )]
unsafe public static extern int mysql_query(void*MySQL, string query);
[ DllImport( "libmySQL.dll", EntryPoint="MySQL_store_result" )]
unsafe public static extern void *mysql_store_result(void *MySQL);
[ DllImport( "libmySQL.dll", EntryPoint="MySQL_free_result" )]
unsafe public static extern void MySQL_free_result(void*result);
[ DllImport( "libmySQL.dll", EntryPoint="MySQL_errno" )]
unsafe public static extern uint mysql_errno(void*MySQL);
[ DllImport( "libmySQL.dll", EntryPoint="MySQL_error" )]
unsafe public static extern string mysql_error(void*MySQL);
[ DllImport( "libmySQL.dll", EntryPoint="MySQL_fIEld_count" )]
unsafe public static extern uint mysql_fIEld_count(void*MySQL);
[ DllImport( "libmySQL.dll", EntryPoint="MySQL_affected_rows" )]
unsafe public static extern ulong mysql_affected_rows(void*MySQL);
[ DllImport( "libmySQL.dll", EntryPoint="MySQL_num_fIElds" )]
unsafe public static extern uint MySQL_num_fIElds(void*result);
[ DllImport( "libmySQL.dll", EntryPoint="MySQL_num_rows" )]
unsafe public static extern ulong MySQL_num_rows(void *result);
[ DllImport( "libmySQL.dll", EntryPoint="MySQL_fetch_fIEld_direct" )]
unsafe public static extern IntPtr MySQL_fetch_field_direct(void*result, uint fIEldnr);
///<returns>Returns a string that represents the clIEnt library version</returns>
[DllImport("libMySQL.dll",CharSet=System.Runtime.InteropServices.CharSet.Ansi,
EntryPoint="MySQL_get_clIEnt_info", ExactSpelling=true)]
public static extern string GetClIEntInfo();
[ DllImport( "libmySQL.dll", EntryPoint="MySQL_fetch_row" )]
unsafe public static extern IntPtr MySQL_fetch_row(void*result);
[ DllImport( "libmySQL.dll", EntryPoint="MySQL_select_db" )]
unsafe public static extern int mysql_select_db(void*MySQL,string dbname);
[ DllImport( "libmySQL.dll", EntryPoint="MySQL_fetch_lengths" )]
unsafe public static extern UInt32 *MySQL_fetch_lengths(void*result);
}
}
