SqlHelper

public static class SqlHelper
{
    //连接字符串
    private static readonly string connStr = ConfigurationManager.ConnectionStrings["mssql"].ConnectionString;


    //1.执行增、删、改的方法：ExecuteNonQuery
    public static int ExecuteNonQuery(string sql, params SqlParameter[] pms)
    {
        using (SqlConnection con = new SqlConnection(connStr))
        {
            using (SqlCommand cmd = new SqlCommand(sql, con))
            {
                if (pms != null)
                {
                    cmd.Parameters.AddRange(pms);
                }
                con.Open();
                return cmd.ExecuteNonQuery();
            }
        }
    }

    //2.封装一个执行返回单个对象的方法：ExecuteScalar()
    public static object ExecuteScalar(string sql, params SqlParameter[] pms)
    {
        using (SqlConnection con = new SqlConnection(connStr))
        {
            using (SqlCommand cmd = new SqlCommand(sql, con))
            {
                if (pms != null)
                {
                    cmd.Parameters.AddRange(pms);
                }
                con.Open();
                return cmd.ExecuteScalar();
            }
        }
    }


    //3.执行查询多行多列的数据的方法：ExecuteReader
    public static SqlDataReader ExecuteReader(string sql, params SqlParameter[] pms)
    {
        SqlConnection con = new SqlConnection(connStr);
        using (SqlCommand cmd = new SqlCommand(sql, con))
        {
            if (pms != null)
            {
                cmd.Parameters.AddRange(pms);
            }
            try
            {
                con.Open();
                return cmd.ExecuteReader(CommandBehavior.CloseConnection);
            }
            catch (Exception)
            {
                con.Close();
                con.Dispose();
                throw;
            }
        }
    }


    //4.执行返回DataTable的方法
    public static DataTable ExecuteDataTable(string sql, params SqlParameter[] pms)
    {
        DataTable dt = new DataTable();
        using (SqlDataAdapter adapter = new SqlDataAdapter(sql, connStr))
        {
            if (pms != null)
            {
                adapter.SelectCommand.Parameters.AddRange(pms);
            }
            adapter.Fill(dt);
        }
        return dt;
    }
}

 【注意】添加全局配置文件：

<connectionStrings >
    <add name ="mssql" connectionString="Server=localhost;DataBase=Login;Uid=sa;Pwd=123456" providerName="System.Data.SqlClient"/>
</connectionStrings>

解释版：

SqlHepler类代码如下：

public static class SqlHelper
{
    /// <summary>
    /// 获取连接字符串
    /// </summary>
    /// <returns>连接字符串</returns>
    public static string GetSqlConnectionString()
    {
        return ConfigurationManager.ConnectionStrings["Sql"].ConnectionString;
    }

    /// <summary>
    /// 封装一个执行的sql 返回受影响的行数
    /// </summary>
    /// <param name="sqlText">执行的sql脚本</param>
    /// <param name="parameters">参数集合</param>
    /// <returns>受影响的行数</returns>
    public static int ExecuteNonQuery(string sqlText, params SqlParameter[] parameters)
    {
        using (SqlConnection conn = new SqlConnection(GetSqlConnectionString()))
        {
            using (SqlCommand cmd = conn.CreateCommand())
            {
                conn.Open();
                cmd.CommandText = sqlText;
                cmd.Parameters.AddRange(parameters);
                return cmd.ExecuteNonQuery();
            }
        }
    }

    /// <summary>
    /// 执行sql，返回查询结果中的第一行第一列的值
    /// </summary>
    /// <param name="sqlText">执行的sql脚本</param>
    /// <param name="parameters">参数集合</param>
    /// <returns>查询结果中的第一行第一列的值</returns>
    public static object ExecuteScalar(string sqlText, params SqlParameter[] parameters)
    {
        using (SqlConnection conn = new SqlConnection(GetSqlConnectionString()))
        {
            using (SqlCommand cmd = conn.CreateCommand())
            {
                conn.Open();
                cmd.CommandText = sqlText;
                cmd.Parameters.AddRange(parameters);
                return cmd.ExecuteScalar();
            }
        }
    }

    /// <summary>
    /// 执行sql 返回一个DataTable
    /// </summary>
    /// <param name="sqlText">执行的sql脚本</param>
    /// <param name="parameters">参数集合</param>
    /// <returns>返回一个DataTable</returns>
    public static DataTable ExecuteDataTable(string sqlText, params SqlParameter[] parameters)
    {
        using (SqlDataAdapter adapter = new SqlDataAdapter(sqlText, GetSqlConnectionString()))
        {
            DataTable dt = new DataTable();
            adapter.SelectCommand.Parameters.AddRange(parameters);
            adapter.Fill(dt);
            return dt;
        }
    }

    /// <summary>
    /// 执行sql脚本
    /// </summary>
    /// <param name="sqlText">执行的sql脚本</param>
    /// <param name="parameters">参数集合</param>
    /// <returns>返回一个SqlDataReader</returns>
    public static SqlDataReader ExecuteReader(string sqlText, params SqlParameter[] parameters)
    {
        //SqlDataReader要求，它读取数据的时候有，它独占它的SqlConnection对象，而且SqlConnection必须是Open状态
        SqlConnection conn = new SqlConnection(GetSqlConnectionString());//不要释放连接，因为后面还需要连接打开状态
        SqlCommand cmd = conn.CreateCommand();
        conn.Open();
        cmd.CommandText = sqlText;
        cmd.Parameters.AddRange(parameters);
        //CommandBehavior.CloseConnection当SqlDataReader释放的时候，顺便把SqlConnection对象也释放掉
        return cmd.ExecuteReader(CommandBehavior.CloseConnection);
    }
}

配置连接字符串：

<connectionStrings>
<add name = "Sql" connectionString = "server=数据库地址;uid=用户名;pwd=密码;database=数据库名" providerName = "System.Data.SqlClient" / >
< / connectionStrings>