DBHelper类连接数据库

 1、执行多条sql语句，实现数据库事务

 2、执行一条计算查询结果语句，返回查询结果（object）

 3、执行查询语句，返回sqldatareader ( 注意：调用该方法后，一定要对sqldatareader进行close )

 4、执行查询语句，返回datatable

 5、执行查询语句，返回dataset

 6、执行存储过程，返回sqldatareader ( 注意：调用该方法后，一定要对sqldatareader进行close )

 7、执行存储过程，带参数

 8、构建 sqlcommand 对象(用来返回一个结果集，而不是一个整数值)

 9、执行存储过程，返回影响的行数

10、创建 sqlcommand 对象实例(用来返回一个整数值)

using system;
using system.collections;
using system.collections.specialized;
using system.data;
using system.data.sqlclient;
using system.configuration;
using system.data.common;
using system.collections.generic;
namespace dal
{
    /// <summary>
    /// 数据访问抽象基础类
    /// copyright (c) 2004-2008 by litianping 
    /// </summary>
    public abstract class dbhelpersql
    {
        //数据库连接字符串(web.config来配置)，可以动态更改connectionstring支持多数据库.        
        //private const string connectionstring = "data source=.;initial catalog=数据库名称;user id=sa;password=数据库密码";
        public static string connectionstring = configurationmanager.connectionstrings["data"].connectionstring;             
        public dbhelpersql()
        {            
        }

        #region 公用方法
        /// <summary>
        /// 判断是否存在某表的某个字段
        /// </summary>
        /// <param name="tablename">表名称</param>
        /// <param name="columnname">列名称</param>
        /// <returns>是否存在</returns>
        public static bool columnexists(string tablename, string columnname)
        {
            string sql = "select count(1) from syscolumns where [id]=object_id('" + tablename + "') and [name]='" + columnname + "'";
            object res = getsingle(sql);
            if (res == null)
            {
                return false;
            }
            return convert.toint32(res) > 0;
        }
        public static int getmaxid(string fieldname, string tablename)
        {
            string strsql = "select max(" + fieldname + ")+1 from " + tablename;
            object obj = getsingle(strsql);
            if (obj == null)
            {
                return 1;
            }
            else
            {
                return int.parse(obj.tostring());
            }
        }
        public static bool exists(string strsql)
        {
            object obj = getsingle(strsql);
            int cmdresult;
            if ((object.equals(obj, null)) || (object.equals(obj, system.dbnull.value)))
            {
                cmdresult = 0;
            }
            else
            {
                cmdresult = int.parse(obj.tostring());
            }
            if (cmdresult == 0)
            {
                return false;
            }
            else
            {
                return true;
            }
        }
        /// <summary>
        /// 表是否存在
        /// </summary>
        /// <param name="tablename"></param>
        /// <returns></returns>
        public static bool tabexists(string tablename)
        {
            string strsql = "select count(*) from sysobjects where id = object_id(n'[" + tablename + "]') and objectproperty(id, n'isusertable') = 1";
            //string strsql = "select count(*) from sys.objects where object_id = object_id(n'[dbo].[" + tablename + "]') and type in (n'u')";
            object obj = getsingle(strsql);
            int cmdresult;
            if ((object.equals(obj, null)) || (object.equals(obj, system.dbnull.value)))
            {
                cmdresult = 0;
            }
            else
            {
                cmdresult = int.parse(obj.tostring());
            }
            if (cmdresult == 0)
            {
                return false;
            }
            else
            {
                return true;
            }
        }
        public static bool exists(string strsql, params sqlparameter[] cmdparms)
        {
            object obj = getsingle(strsql, cmdparms);
            int cmdresult;
            if ((object.equals(obj, null)) || (object.equals(obj, system.dbnull.value)))
            {
                cmdresult = 0;
            }
            else
            {
                cmdresult = int.parse(obj.tostring());
            }
            if (cmdresult == 0)
            {
                return false;
            }
            else
            {
                return true;
            }
        }
        #endregion

        #region  执行简单sql语句

        /// <summary>
        /// 执行sql语句，返回影响的记录数
        /// </summary>
        /// <param name="sqlstring">sql语句</param>
        /// <returns>影响的记录数</returns>
        public static int executesql(string sqlstring)
        {
            using (sqlconnection connection = new sqlconnection(connectionstring))
            {
                using (sqlcommand cmd = new sqlcommand(sqlstring, connection))
                {
                    try
                    {
                        connection.open();
                        int rows = cmd.executenonquery();
                        return rows;
                    }
                    catch (system.data.sqlclient.sqlexception e)
                    {
                        connection.close();
                        throw e;
                    }
                }
            }
        }

        public static int executesqlbytime(string sqlstring, int times)
        {
            using (sqlconnection connection = new sqlconnection(connectionstring))
            {
                using (sqlcommand cmd = new sqlcommand(sqlstring, connection))
                {
                    try
                    {
                        connection.open();
                        cmd.commandtimeout = times;
                        int rows = cmd.executenonquery();
                        return rows;
                    }
                    catch (system.data.sqlclient.sqlexception e)
                    {
                        connection.close();
                        throw e;
                    }
                }
            }
        }
      

        /// <summary>
        /// 执行多条sql语句，实现数据库事务。
        /// </summary>
        /// <param name="sqlstringlist">多条sql语句</param>        
        public static int executesqltran(list<string> sqlstringlist)
        {
            using (sqlconnection conn = new sqlconnection(connectionstring))
            {
                conn.open();
                sqlcommand cmd = new sqlcommand();
                cmd.connection = conn;
                sqltransaction tx = conn.begintransaction();
                cmd.transaction = tx;
                try
                {
                    int count = 0;
                    for (int n = 0; n < sqlstringlist.count; n++)
                    {
                        string strsql = sqlstringlist[n];
                        if (strsql.trim().length > 1)
                        {
                            cmd.commandtext = strsql;
                            count += cmd.executenonquery();
                        }
                    }
                    tx.commit();
                    return count;
                }
                catch
                {
                    tx.rollback();
                    return 0;
                }
            }
        }
        /// <summary>
        /// 执行带一个存储过程参数的的sql语句。
        /// </summary>
        /// <param name="sqlstring">sql语句</param>
        /// <param name="content">参数内容,比如一个字段是格式复杂的文章，有特殊符号，可以通过这个方式添加</param>
        /// <returns>影响的记录数</returns>
        public static int executesql(string sqlstring, string content)
        {
            using (sqlconnection connection = new sqlconnection(connectionstring))
            {
                sqlcommand cmd = new sqlcommand(sqlstring, connection);
                system.data.sqlclient.sqlparameter myparameter = new system.data.sqlclient.sqlparameter("@content", sqldbtype.ntext);
                myparameter.value = content;
                cmd.parameters.add(myparameter);
                try
                {
                    connection.open();
                    int rows = cmd.executenonquery();
                    return rows;
                }
                catch (system.data.sqlclient.sqlexception e)
                {
                    throw e;
                }
                finally
                {
                    cmd.dispose();
                    connection.close();
                }
            }
        }
        /// <summary>
        /// 执行带一个存储过程参数的的sql语句。
        /// </summary>
        /// <param name="sqlstring">sql语句</param>
        /// <param name="content">参数内容,比如一个字段是格式复杂的文章，有特殊符号，可以通过这个方式添加</param>
        /// <returns>影响的记录数</returns>
        public static object executesqlget(string sqlstring, string content)
        {
            using (sqlconnection connection = new sqlconnection(connectionstring))
            {
                sqlcommand cmd = new sqlcommand(sqlstring, connection);
                system.data.sqlclient.sqlparameter myparameter = new system.data.sqlclient.sqlparameter("@content", sqldbtype.ntext);
                myparameter.value = content;
                cmd.parameters.add(myparameter);
                try
                {
                    connection.open();
                    object obj = cmd.executescalar();
                    if ((object.equals(obj, null)) || (object.equals(obj, system.dbnull.value)))
                    {
                        return null;
                    }
                    else
                    {
                        return obj;
                    }
                }
                catch (system.data.sqlclient.sqlexception e)
                {
                    throw e;
                }
                finally
                {
                    cmd.dispose();
                    connection.close();
                }
            }
        }
        /// <summary>
        /// 向数据库里插入图像格式的字段(和上面情况类似的另一种实例)
        /// </summary>
        /// <param name="strsql">sql语句</param>
        /// <param name="fs">图像字节,数据库的字段类型为image的情况</param>
        /// <returns>影响的记录数</returns>
        public static int executesqlinsertimg(string strsql, byte[] fs)
        {
            using (sqlconnection connection = new sqlconnection(connectionstring))
            {
                sqlcommand cmd = new sqlcommand(strsql, connection);
                system.data.sqlclient.sqlparameter myparameter = new system.data.sqlclient.sqlparameter("@fs", sqldbtype.image);
                myparameter.value = fs;
                cmd.parameters.add(myparameter);
                try
                {
                    connection.open();
                    int rows = cmd.executenonquery();
                    return rows;
                }
                catch (system.data.sqlclient.sqlexception e)
                {
                    throw e;
                }
                finally
                {
                    cmd.dispose();
                    connection.close();
                }
            }
        }

        /// <summary>
        /// 执行一条计算查询结果语句，返回查询结果（object）。
        /// </summary>
        /// <param name="sqlstring">计算查询结果语句</param>
        /// <returns>查询结果（object）</returns>
        public static object getsingle(string sqlstring)
        {
            using (sqlconnection connection = new sqlconnection(connectionstring))
            {
                using (sqlcommand cmd = new sqlcommand(sqlstring, connection))
                {
                    try
                    {
                        connection.open();
                        object obj = cmd.executescalar();
                        if ((object.equals(obj, null)) || (object.equals(obj, system.dbnull.value)))
                        {
                            return null;
                        }
                        else
                        {
                            return obj;
                        }
                    }
                    catch (system.data.sqlclient.sqlexception e)
                    {
                        connection.close();
                        throw e;
                    }
                }
            }
        }
        public static object getsingle(string sqlstring, int times)
        {
            using (sqlconnection connection = new sqlconnection(connectionstring))
            {
                using (sqlcommand cmd = new sqlcommand(sqlstring, connection))
                {
                    try
                    {
                        connection.open();
                        cmd.commandtimeout = times;
                        object obj = cmd.executescalar();
                        if ((object.equals(obj, null)) || (object.equals(obj, system.dbnull.value)))
                        {
                            return null;
                        }
                        else
                        {
                            return obj;
                        }
                    }
                    catch (system.data.sqlclient.sqlexception e)
                    {
                        connection.close();
                        throw e;
                    }
                }
            }
        }
        /// <summary>
        /// 执行查询语句，返回sqldatareader ( 注意：调用该方法后，一定要对sqldatareader进行close )
        /// </summary>
        /// <param name="strsql">查询语句</param>
        /// <returns>sqldatareader</returns>
        public static sqldatareader executereader(string strsql)
        {
            sqlconnection connection = new sqlconnection(connectionstring);
            sqlcommand cmd = new sqlcommand(strsql, connection);
            try
            {
                connection.open();
                sqldatareader myreader = cmd.executereader(commandbehavior.closeconnection);
                return myreader;
            }
            catch (system.data.sqlclient.sqlexception e)
            {
                throw e;
            }   

        }
        /// <summary>
        /// 执行查询语句，返回dataset
        /// </summary>
        /// <param name="sqlstring">查询语句</param>
        /// <returns>dataset</returns>
        public static dataset query(string sqlstring)
        {
            using (sqlconnection connection = new sqlconnection(connectionstring))
            {
                dataset ds = new dataset();
                try
                {
                    connection.open();
                    sqldataadapter command = new sqldataadapter(sqlstring, connection);
                    command.fill(ds, "ds");
                }
                catch (system.data.sqlclient.sqlexception ex)
                {
                    throw new exception(ex.message);
                }
                return ds;
            }
        }


        /// <summary>
        /// 执行查询语句，返回pagedataset
        /// </summary>
        /// <param name="sqlstring">查询语句</param>
        /// <returns>dataset</returns>
        public static dataset pagequery(string sqlstring, int pageindex, int pagesize)
        {
            using (sqlconnection connection = new sqlconnection(connectionstring))
            {
                dataset ds = new dataset();
                try
                {
                    connection.open();
                    sqldataadapter command = new sqldataadapter(sqlstring, connection);
                    command.fill(ds, pageindex, pagesize, "ds");
                }
                catch (system.data.sqlclient.sqlexception ex)
                {
                    throw new exception(ex.message);
                }
                return ds;
            }
        }


        public static dataset query(string sqlstring, int times)
        {
            using (sqlconnection connection = new sqlconnection(connectionstring))
            {
                dataset ds = new dataset();
                try
                {
                    connection.open();
                    sqldataadapter command = new sqldataadapter(sqlstring, connection);
                    command.selectcommand.commandtimeout = times;
                    command.fill(ds, "ds");
                }
                catch (system.data.sqlclient.sqlexception ex)
                {
                    throw new exception(ex.message);
                }
                return ds;
            }
        }



        #endregion

        #region 执行带参数的sql语句

        /// <summary>
        /// 执行sql语句，返回影响的记录数
        /// </summary>
        /// <param name="sqlstring">sql语句</param>
        /// <returns>影响的记录数</returns>
        public static int executesql(string sqlstring, params sqlparameter[] cmdparms)
        {
            using (sqlconnection connection = new sqlconnection(connectionstring))
            {
                using (sqlcommand cmd = new sqlcommand())
                {
                    try
                    {
                        preparecommand(cmd, connection, null, sqlstring, cmdparms);
                        int rows = cmd.executenonquery();
                        cmd.parameters.clear();
                        return rows;
                    }
                    catch (system.data.sqlclient.sqlexception e)
                    {
                        throw e;
                    }
                }
            }
        }


        /// <summary>
        /// 执行多条sql语句，实现数据库事务。
        /// </summary>
        /// <param name="sqlstringlist">sql语句的哈希表（key为sql语句，value是该语句的sqlparameter[]）</param>
        public static void executesqltran(hashtable sqlstringlist)
        {
            using (sqlconnection conn = new sqlconnection(connectionstring))
            {
                conn.open();
                using (sqltransaction trans = conn.begintransaction())
                {
                    sqlcommand cmd = new sqlcommand();
                    try
                    {
                        //循环
                        foreach (dictionaryentry myde in sqlstringlist)
                        {
                            string cmdtext = myde.key.tostring();
                            sqlparameter[] cmdparms = (sqlparameter[])myde.value;
                            preparecommand(cmd, conn, trans, cmdtext, cmdparms);
                            int val = cmd.executenonquery();
                            cmd.parameters.clear();
                        }
                        trans.commit();
                    }
                    catch
                    {
                        trans.rollback();
                        throw;
                    }
                }
            }
        }
        /// <summary>
        /// 执行多条sql语句，实现数据库事务。
        /// </summary>
        /// <param name="sqlstringlist">sql语句的哈希表（key为sql语句，value是该语句的sqlparameter[]）</param>
        public static void executesqltranwithindentity(hashtable sqlstringlist)
        {
            using (sqlconnection conn = new sqlconnection(connectionstring))
            {
                conn.open();
                using (sqltransaction trans = conn.begintransaction())
                {
                    sqlcommand cmd = new sqlcommand();
                    try
                    {
                        int indentity = 0;
                        //循环
                        foreach (dictionaryentry myde in sqlstringlist)
                        {
                            string cmdtext = myde.key.tostring();
                            sqlparameter[] cmdparms = (sqlparameter[])myde.value;
                            foreach (sqlparameter q in cmdparms)
                            {
                                if (q.direction == parameterdirection.inputoutput)
                                {
                                    q.value = indentity;
                                }
                            }
                            preparecommand(cmd, conn, trans, cmdtext, cmdparms);
                            int val = cmd.executenonquery();
                            foreach (sqlparameter q in cmdparms)
                            {
                                if (q.direction == parameterdirection.output)
                                {
                                    indentity = convert.toint32(q.value);
                                }
                            }
                            cmd.parameters.clear();
                        }
                        trans.commit();
                    }
                    catch
                    {
                        trans.rollback();
                        throw;
                    }
                }
            }
        }
        /// <summary>
        /// 执行一条计算查询结果语句，返回查询结果（object）。
        /// </summary>
        /// <param name="sqlstring">计算查询结果语句</param>
        /// <returns>查询结果（object）</returns>
        public static object getsingle(string sqlstring, params sqlparameter[] cmdparms)
        {
            using (sqlconnection connection = new sqlconnection(connectionstring))
            {
                using (sqlcommand cmd = new sqlcommand())
                {
                    try
                    {
                        preparecommand(cmd, connection, null, sqlstring, cmdparms);
                        object obj = cmd.executescalar();
                        cmd.parameters.clear();
                        if ((object.equals(obj, null)) || (object.equals(obj, system.dbnull.value)))
                        {
                            return null;
                        }
                        else
                        {
                            return obj;
                        }
                    }
                    catch (system.data.sqlclient.sqlexception e)
                    {
                        throw e;
                    }
                }
            }
        }

        /// <summary>
        /// 执行查询语句，返回sqldatareader ( 注意：调用该方法后，一定要对sqldatareader进行close )
        /// </summary>
        /// <param name="strsql">查询语句</param>
        /// <returns>sqldatareader</returns>
        public static sqldatareader executereader(string sqlstring, params sqlparameter[] cmdparms)
        {
            sqlconnection connection = new sqlconnection(connectionstring);
            sqlcommand cmd = new sqlcommand();
            try
            {
                preparecommand(cmd, connection, null, sqlstring, cmdparms);
                sqldatareader myreader = cmd.executereader(commandbehavior.closeconnection);
                cmd.parameters.clear();
                return myreader;
            }
            catch (system.data.sqlclient.sqlexception e)
            {
                throw e;
            }
            //            finally
            //            {
            //                cmd.dispose();
            //                connection.close();
            //            }    

        }

        /// <summary>
        /// 执行查询语句，返回datatable
        /// </summary>
        /// <param name="sqlstring">查询语句</param>
        /// <returns>datatable</returns>
        public static datatable getdatatable(string sqlstring, params sqlparameter[] cmdparms)
        {
            using (sqlconnection connection = new sqlconnection(connectionstring))
            {
                sqlcommand cmd = new sqlcommand();
                preparecommand(cmd, connection, null, sqlstring, cmdparms);
                using (sqldataadapter da = new sqldataadapter(cmd))
                {
                    dataset ds = new dataset();
                    try
                    {
                        da.fill(ds, "ds");
                        cmd.parameters.clear();
                    }
                    catch (system.data.sqlclient.sqlexception ex)
                    {
                        throw new exception(ex.message);
                    }
                    return ds.tables[0];
                }
            }
        }

        /// <summary>
        /// 执行查询语句，返回dataset
        /// </summary>
        /// <param name="sqlstring">查询语句</param>
        /// <returns>dataset</returns>
        public static dataset pagequery(string sqlstring, int pageindex, int pagesize, params sqlparameter[] cmdparms)
        {
            using (sqlconnection connection = new sqlconnection(connectionstring))
            {
                sqlcommand cmd = new sqlcommand();
                preparecommand(cmd, connection, null, sqlstring, cmdparms);
                using (sqldataadapter da = new sqldataadapter(cmd))
                {
                    dataset ds = new dataset();
                    try
                    {
                        da.fill(ds,pageindex, pagesize, "ds");
                        cmd.parameters.clear();
                    }
                    catch (system.data.sqlclient.sqlexception ex)
                    {
                        throw new exception(ex.message);
                    }
                    return ds;
                }
            }
        }
        private static void preparecommand(sqlcommand cmd, sqlconnection conn, sqltransaction trans, string cmdtext, sqlparameter[] cmdparms)
        {
            if (conn.state != connectionstate.open)
                conn.open();
            cmd.connection = conn;
            cmd.commandtext = cmdtext;
            if (trans != null)
                cmd.transaction = trans;
            cmd.commandtype = commandtype.text;//cmdtype;
            if (cmdparms != null)
            {


                foreach (sqlparameter parameter in cmdparms)
                {
                    if ((parameter.direction == parameterdirection.inputoutput || parameter.direction == parameterdirection.input) &&
                        (parameter.value == null))
                    {
                        parameter.value = dbnull.value;
                    }
                    cmd.parameters.add(parameter);
                }
            }
        }

        #endregion

        #region 存储过程操作

        /// <summary>
        /// 执行存储过程，返回sqldatareader ( 注意：调用该方法后，一定要对sqldatareader进行close )
        /// </summary>
        /// <param name="storedprocname">存储过程名</param>
        /// <param name="parameters">存储过程参数</param>
        /// <returns>sqldatareader</returns>
        public static sqldatareader runprocedure(string storedprocname, idataparameter[] parameters)
        {
            sqlconnection connection = new sqlconnection(connectionstring);
            sqldatareader returnreader;
            connection.open();
            sqlcommand command = buildquerycommand(connection, storedprocname, parameters);
            command.commandtype = commandtype.storedprocedure;
            returnreader = command.executereader(commandbehavior.closeconnection);
            return returnreader;
            
        }


        /// <summary>
        /// 执行存储过程
        /// </summary>
        /// <param name="storedprocname">存储过程名</param>
        /// <param name="parameters">存储过程参数</param>
        /// <param name="tablename">dataset结果中的表名</param>
        /// <returns>dataset</returns>
        public static dataset runprocedure(string storedprocname, idataparameter[] parameters, string tablename)
        {
            using (sqlconnection connection = new sqlconnection(connectionstring))
            {
                dataset dataset = new dataset();
                connection.open();
                sqldataadapter sqlda = new sqldataadapter();
                sqlda.selectcommand = buildquerycommand(connection, storedprocname, parameters);
                sqlda.fill(dataset, tablename);
                connection.close();
                return dataset;
            }
        }
        public static dataset runprocedure(string storedprocname, idataparameter[] parameters, string tablename, int times)
        {
            using (sqlconnection connection = new sqlconnection(connectionstring))
            {
                dataset dataset = new dataset();
                connection.open();
                sqldataadapter sqlda = new sqldataadapter();
                sqlda.selectcommand = buildquerycommand(connection, storedprocname, parameters);
                sqlda.selectcommand.commandtimeout = times;
                sqlda.fill(dataset, tablename);
                connection.close();
                return dataset;
            }
        }


        /// <summary>
        /// 构建 sqlcommand 对象(用来返回一个结果集，而不是一个整数值)
        /// </summary>
        /// <param name="connection">数据库连接</param>
        /// <param name="storedprocname">存储过程名</param>
        /// <param name="parameters">存储过程参数</param>
        /// <returns>sqlcommand</returns>
        private static sqlcommand buildquerycommand(sqlconnection connection, string storedprocname, idataparameter[] parameters)
        {
            sqlcommand command = new sqlcommand(storedprocname, connection);
            command.commandtype = commandtype.storedprocedure;
            foreach (sqlparameter parameter in parameters)
            {
                if (parameter != null)
                {
                    // 检查未分配值的输出参数,将其分配以dbnull.value.
                    if ((parameter.direction == parameterdirection.inputoutput || parameter.direction == parameterdirection.input) &&
                        (parameter.value == null))
                    {
                        parameter.value = dbnull.value;
                    }
                    command.parameters.add(parameter);
                }
            }

            return command;
        }

        /// <summary>
        /// 执行存储过程，返回影响的行数        
        /// </summary>
        /// <param name="storedprocname">存储过程名</param>
        /// <param name="parameters">存储过程参数</param>
        /// <param name="rowsaffected">影响的行数</param>
        /// <returns></returns>
        public static int runprocedure(string storedprocname, idataparameter[] parameters, out int rowsaffected)
        {
            using (sqlconnection connection = new sqlconnection(connectionstring))
            {
                int result;
                connection.open();
                sqlcommand command = buildintcommand(connection, storedprocname, parameters);
                rowsaffected = command.executenonquery();
                result = (int)command.parameters["returnvalue"].value;
                //connection.close();
                return result;
            }
        }

        /// <summary>
        /// 创建 sqlcommand 对象实例(用来返回一个整数值)    
        /// </summary>
        /// <param name="storedprocname">存储过程名</param>
        /// <param name="parameters">存储过程参数</param>
        /// <returns>sqlcommand 对象实例</returns>
        private static sqlcommand buildintcommand(sqlconnection connection, string storedprocname, idataparameter[] parameters)
        {
            sqlcommand command = buildquerycommand(connection, storedprocname, parameters);
            command.parameters.add(new sqlparameter("returnvalue",
                sqldbtype.int, 4, parameterdirection.returnvalue,
                false, 0, 0, string.empty, datarowversion.default, null));
            return command;
        }
        #endregion

    }

}