实例讲解：.NET如何访问MySQL数据库

2022-07-15 80酷酷网 80kuku.com

　　mysql|访问|数据|数据库

　　.NET的数据库天然支持MSSQLServer，但是并非其他数据库不支持，而是微软基于自身利益需要，在支持、营销上推自己的数据库产品;但是作为平台战略，他并非排斥其他数据库，而是参考java体系提出了一套数据库访问规范，让各个第三方进行开发，提供特定的驱动。

　　MySQL是免费的数据库，在成本上具有无可替代的优势，但是目前来讲，并没有提供。微软把MySQL当作ODBC数据库，可以按照ODBC.Net规范进行访问，具体参考

　　http://www.microsoft.com/china/community/Columns/Luyan/6.mspx

　　而实际上，针对ODBC。Net的需要配置DSN的麻烦，而是出现了一个开源的系统MySQLDriverCS，对MySQL的开发进行了封装，实现了.net环境下对于MySQL数据库系统的访问。

　　http://sourceforge.net/projects/mysqldrivercs/

　　通过阅读源代码，我们看到MySQLDriverCS的思路是利用C函数的底层库来操纵数据库的，通常提供对MySQL数据库的访问的数据库的C DLL是名为libmySQL.dll的驱动文件，MySQLDriverCS作为一个.net库进行封装C风格的驱动。

　　具体如何进行呢?

　　打开工程后，我们看到其中有一个比较特殊的.cs文件CPrototypes.cs：

#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*/#endregionusing 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); }}

　　基本上是将C风格的基础数据结构进行.net的重新定义，然后通过InteropServices进行访问。　　具体如何利用这个库进行操作，可以参考其中的例子。