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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.

SqlServer调用数据库

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using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Configuration;
using System.Data;
using System.Data.SqlClient;

namespace Dal
{
    public static class DBHelper
    {
        public static string strCon = "Data Source=.;Initial Catalog=Week3;Integrated Security=True";
        /// <summary>
        /// 增删改

        /// </summary>
        /// <param name="sql">sql语句</param>
        /// <param name="str">连接字符串</param>
        /// <returns></returns>
        public static int ExecuteNonQuery(string sql)
        {
            //实例化连接对象
            SqlConnection conn = new SqlConnection(strCon);
            int result = 0;
            try
            {
                conn.Open();
                //实例化命令对象
                SqlCommand cmd = new SqlCommand(sql, conn);
                //执行命令
                result = cmd.ExecuteNonQuery();
            }
            catch (Exception)
            {

                throw;
            }
            finally
            {
                conn.Close();
            }
            return result;
        }
        /// <summary>
        /// 获取表格
        /// </summary>
        /// <param name="sql">sql语句</param>
        /// <param name="str">连接字符串</param>
        /// <returns></returns>
        public static DataTable GetDataTable(string sql)
        {
            //实例化连接对象
            SqlConnection conn = new SqlConnection(strCon);
            DataTable dt = new DataTable();

            try
            {
                //实例化适配器
                SqlDataAdapter sda = new SqlDataAdapter(sql, conn);
                sda.Fill(dt);

            }
            catch (Exception)
            {

                throw;
            }
            return dt;
        }
        /// <summary>
        /// 
        /// </summary>
        /// <param name="sql">sql语句</param>
        /// <param name="str">连接字符串</param>
        /// <returns></returns>
        public static SqlDataReader GetDataReader(string sql)
        {
            //实例化连接对象
            SqlConnection conn = new SqlConnection(strCon);
            SqlDataReader sdr;
            try
            {
                conn.Open();
                //实例化命令对象
                SqlCommand cmd = new SqlCommand(sql, conn);
                sdr = cmd.ExecuteReader();

            }
            catch (Exception)
            {

                throw;
            }
            return sdr;
        }
        /// <summary>
        /// 返回单行单列
        /// </summary>
        /// <param name="sql">sql语句</param>
        /// <param name="str">连接字符串</param>
        /// <returns></returns>
        public static int ExecuteScalar(string sql)
        {
            //实例化连接对象
            SqlConnection conn = new SqlConnection(strCon);
            int result = 0;
            try
            {
                conn.Open();
                //实例化命令对象
                SqlCommand cmd = new SqlCommand(sql, conn);
                result = Convert.ToInt32(cmd.ExecuteScalar());
            }
            catch (Exception)
            {

                throw;
            }
            finally
            {

                conn.Close();
            }
            return result;
        }



        /// <summary>
        /// 信息分页显示
        /// </summary>
        /// <returns></returns>
        public static DataTable GetInfoByPage(int Pageindex, int PageSize)
        {
            string sql = string.Format(@"select top {0}* from(
                    select XinXi.*,ROW_NUMBER() over(order by XinXi.XinXiId) pid ,Type.Name from Type 
                    inner join XinXi on Type.Id= XinXi.TypeId ) as temp 
                    where temp.pid>{1}", PageSize, (Pageindex - 1) * PageSize);
            return DBHelper.GetDataTable(sql);
        }
        /// <summary>
        /// 获取个数
        /// </summary>
        /// <returns></returns>
        public static int GetCount()
        {
            string sql = "select count(XinXi.XinXiId) from Type   inner join XinXi on Type.Id= XinXi.TypeId";
            return DBHelper.ExecuteScalar(sql);

        }
    }
}
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SqlServer调用数据库存储过程

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using System;
using System.Collections.Generic;
using System.Data;
using System.Data.SqlClient;
using System.Linq;
using System.Web;

namespace Unit07_Service
{
    public class DBHelper
    {

        public static string connStr = "Data Source=.;Initial Catalog=DB_News;Integrated Security=True";
        public static SqlConnection cnn = new SqlConnection(connStr);

        /// <summary>
        /// 执行增删改的操作
        /// </summary>
        /// <param name="sql">sql命令</param>
        /// <returns>受影响的行数</returns>
        public static int ExecuteNonQuery(string sql)
        {
            Open();
            SqlCommand command = new SqlCommand(sql, cnn);
            int result = command.ExecuteNonQuery();
            cnn.Close();
            return result;
        }
        /// <summary>
        /// 查询单个值

        /// </summary>
        /// <param name="sql"></param>
        /// <returns></returns>
        public static object ExecuteScalar(string sql)
        {
            Open();
            SqlCommand command = new SqlCommand(sql, cnn);
            object result = command.ExecuteScalar();
            cnn.Close();
            return result;
        }
        /// <summary>
        /// 返回数据表

        /// </summary>
        /// <param name="sql"></param>
        /// <returns></returns>
        public static DataTable GetDataTable(string sql)
        {
            SqlDataAdapter adapter = new SqlDataAdapter(sql, cnn);
            DataSet ds = new DataSet();
            adapter.Fill(ds);
            return ds.Tables[0];
        }
        /// <summary>
        /// 返回DataReader对象，使用结束后，勿忘关闭DataReader与数据库
        /// </summary>
        /// <param name="sql"></param>
        /// <returns></returns>
        public static SqlDataReader GetDataReader(string sql)
        {
            Open();
            SqlCommand command = new SqlCommand(sql, cnn);
            return command.ExecuteReader();
        }
        /// <summary>
        /// 打开数据库

        /// </summary>
        public static void Open()
        {
            if (cnn.State == ConnectionState.Broken || cnn.State == ConnectionState.Open)
            {
                cnn.Close();
            }
            cnn.Open();
        }

        /// <summary>
        /// 打开数据库

        /// </summary>
        public static void Close()
        {
            cnn.Close();
        }

        /// <summary>
        /// 使用存储过程查询数据结果
        /// </summary>
        /// <param name="sql"></param>
        /// <param name="paras"></param>
        /// <returns></returns>
        public static DataTable GetDataTable(string procName, SqlParameter[] paras = null)
        {
            Open();
            SqlCommand command = new SqlCommand(procName, cnn);
            command.CommandType = CommandType.StoredProcedure;

            if (paras != null)
            {
                command.Parameters.AddRange(paras);
            }
            SqlDataAdapter adapter = new SqlDataAdapter(command);
            DataSet ds = new DataSet();
            adapter.Fill(ds);
            Close();
            return ds.Tables[0];
        }

        /// <summary>
        /// 使用存储过程执行增删改

        /// </summary>
        /// <param name="sql"></param>
        /// <param name="paras"></param>
        /// <returns></returns>
        public static int ExecuteNonQuery(string procName, SqlParameter[] paras)
        {
            Open();
            SqlCommand command = new SqlCommand(procName, cnn);
            command.CommandType = CommandType.StoredProcedure;
            command.Parameters.AddRange(paras);

            int result = command.ExecuteNonQuery();
            Close();

            return result;


        }
    }
}
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MySql调用数据库

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using System;
using System.Collections;
using System.Collections.Specialized;
using System.Data;
using MySql.Data.MySqlClient;
using System.Configuration;
using System.Data.Common;
using System.Collections.Generic;
namespace Student_API.Controllers
{
    /// <summary>
    /// 数据访问抽象基础类

    /// Copyright (C) 2004-2008 By LiTianPing 
    /// </summary>
    public abstract class DbHelperMySQL
    {
        //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.        
        public static string connectionString = "server=127.0.0.1;user id=root;pwd=root;database=06a_exam";
        public DbHelperMySQL()
        {            
        }

        #region 公用方法
        /// <summary>
        /// 得到最大值

        /// </summary>
        /// <param name="FieldName"></param>
        /// <param name="TableName"></param>
        /// <returns></returns>
        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());
            }
        }
        /// <summary>
        /// 是否存在
        /// </summary>
        /// <param name="strSql"></param>
        /// <returns></returns>
        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>
        /// 是否存在（基于MySqlParameter）

        /// </summary>
        /// <param name="strSql"></param>
        /// <param name="cmdParms"></param>
        /// <returns></returns>
        public static bool Exists(string strSql, params MySqlParameter[] 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 (MySqlConnection connection = new MySqlConnection(connectionString))
            {
                using (MySqlCommand cmd = new MySqlCommand(SQLString, connection))
                {
                    try
                    {
                        connection.Open();
                        int rows = cmd.ExecuteNonQuery();
                        return rows;
                    }
                    catch (MySql.Data.MySqlClient.MySqlException e)
                    {
                        connection.Close();
                        throw e;
                    }
                }
            }
        }

        public static int ExecuteSqlByTime(string SQLString, int Times)
        {
            using (MySqlConnection connection = new MySqlConnection(connectionString))
            {
                using (MySqlCommand cmd = new MySqlCommand(SQLString, connection))
                {
                    try
                    {
                        connection.Open();
                        cmd.CommandTimeout = Times;
                        int rows = cmd.ExecuteNonQuery();
                        return rows;
                    }
                    catch (MySql.Data.MySqlClient.MySqlException 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 (MySqlConnection conn = new MySqlConnection(connectionString))
            {
                conn.Open();
                MySqlCommand cmd = new MySqlCommand();
                cmd.Connection = conn;
                MySqlTransaction 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 (MySqlConnection connection = new MySqlConnection(connectionString))
            {
                MySqlCommand cmd = new MySqlCommand(SQLString, connection);
                MySql.Data.MySqlClient.MySqlParameter myParameter = new MySql.Data.MySqlClient.MySqlParameter("@content", SqlDbType.NText);
                myParameter.Value = content;
                cmd.Parameters.Add(myParameter);
                try
                {
                    connection.Open();
                    int rows = cmd.ExecuteNonQuery();
                    return rows;
                }
                catch (MySql.Data.MySqlClient.MySqlException 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 (MySqlConnection connection = new MySqlConnection(connectionString))
            {
                MySqlCommand cmd = new MySqlCommand(SQLString, connection);
                MySql.Data.MySqlClient.MySqlParameter myParameter = new MySql.Data.MySqlClient.MySqlParameter("@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 (MySql.Data.MySqlClient.MySqlException 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 (MySqlConnection connection = new MySqlConnection(connectionString))
            {
                MySqlCommand cmd = new MySqlCommand(strSQL, connection);
                MySql.Data.MySqlClient.MySqlParameter myParameter = new MySql.Data.MySqlClient.MySqlParameter("@fs", SqlDbType.Image);
                myParameter.Value = fs;
                cmd.Parameters.Add(myParameter);
                try
                {
                    connection.Open();
                    int rows = cmd.ExecuteNonQuery();
                    return rows;
                }
                catch (MySql.Data.MySqlClient.MySqlException 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 (MySqlConnection connection = new MySqlConnection(connectionString))
            {
                using (MySqlCommand cmd = new MySqlCommand(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 (MySql.Data.MySqlClient.MySqlException e)
                    {
                        connection.Close();
                        throw e;
                    }
                }
            }
        }
        public static object GetSingle(string SQLString, int Times)
        {
            using (MySqlConnection connection = new MySqlConnection(connectionString))
            {
                using (MySqlCommand cmd = new MySqlCommand(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 (MySql.Data.MySqlClient.MySqlException e)
                    {
                        connection.Close();
                        throw e;
                    }
                }
            }
        }
        /// <summary>
        /// 执行查询语句，返回MySqlDataReader ( 注意：调用该方法后，一定要对MySqlDataReader进行Close )
        /// </summary>
        /// <param name="strSQL">查询语句</param>
        /// <returns>MySqlDataReader</returns>
        public static MySqlDataReader ExecuteReader(string strSQL)
        {
            MySqlConnection connection = new MySqlConnection(connectionString);
            MySqlCommand cmd = new MySqlCommand(strSQL, connection);
            try
            {
                connection.Open();
                MySqlDataReader myReader = cmd.ExecuteReader(CommandBehavior.CloseConnection);
                return myReader;
            }
            catch (MySql.Data.MySqlClient.MySqlException 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 (MySqlConnection connection = new MySqlConnection(connectionString))
            {
                DataSet ds = new DataSet();
                try
                {
                    connection.Open();
                    MySqlDataAdapter command = new MySqlDataAdapter(SQLString, connection);
                    command.Fill(ds, "ds");
                }
                catch (MySql.Data.MySqlClient.MySqlException ex)
                {
                    throw new Exception(ex.Message);
                }
                return ds;
            }
        }
        public static DataSet Query(string SQLString, int Times)
        {
            using (MySqlConnection connection = new MySqlConnection(connectionString))
            {
                DataSet ds = new DataSet();
                try
                {
                    connection.Open();
                    MySqlDataAdapter command = new MySqlDataAdapter(SQLString, connection);
                    command.SelectCommand.CommandTimeout = Times;
                    command.Fill(ds, "ds");
                }
                catch (MySql.Data.MySqlClient.MySqlException 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 MySqlParameter[] cmdParms)
        {
            using (MySqlConnection connection = new MySqlConnection(connectionString))
            {
                using (MySqlCommand cmd = new MySqlCommand())
                {
                    try
                    {
                        PrepareCommand(cmd, connection, null, SQLString, cmdParms);
                        int rows = cmd.ExecuteNonQuery();
                        cmd.Parameters.Clear();
                        return rows;
                    }
                    catch (MySql.Data.MySqlClient.MySqlException e)
                    {
                        throw e;
                    }
                }
            }
        }


        /// <summary>
        /// 执行多条SQL语句，实现数据库事务。
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