收集C#常用类：自己写的一个DBHelper类

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

namespace _2016_11_21
{
    public static class DBHelper
    {
        //从配置文件里读连接数据库语句
        static string sql = ConfigurationManager.ConnectionStrings["sqlstr"].ConnectionString;

        /// <summary>
        /// 带参数、事务处理的sql增删改
        /// </summary>
        /// <param name="str">SQL语句</param>
        /// <param name="para">参数数组</param>
        /// <returns>true/false</returns>
        public static bool IDUBySql(string str, SqlParameter[] para)
        {
            bool fa = false;
            using (SqlConnection sqlconn = new SqlConnection(sql))
            {
                using (SqlCommand sqlcomm = new SqlCommand(sql, sqlconn))
                {
                    try
                    {
                        sqlconn.Open();
                        if (para != null)
                        {
                            sqlcomm.Parameters.AddRange(para);
                        }
                        //开启事物
                        sqlcomm.Transaction = sqlconn.BeginTransaction();
                        fa = sqlcomm.ExecuteNonQuery() > 0 ? true : false;
                        //提交事物
                        sqlcomm.Transaction.Commit();
                    }
                    catch (SqlException ex)
                    {
                        sqlcomm.Transaction.Rollback();
                        throw ex;
                    }
                    finally
                    {
                        sqlconn.Close();
                    }
                }
            }
            return fa;
        }
        /// <summary>
        /// 带参数的SQL查询语句
        /// </summary>
        /// <param name="str">SQL语句</param>
        /// <param name="para">参数数组</param>
        /// <returns>返回一个DataTable</returns>
        public static DataTable GetTableBySql(string str, SqlParameter[] para)
        {
            DataTable dt = new DataTable();

            using (SqlConnection sqlconn = new SqlConnection(sql))
            {
                using (SqlCommand sqlcomm = new SqlCommand(str, sqlconn))
                {
                    if (para != null)
                    {
                        sqlcomm.Parameters.AddRange(para);
                    }
                    using (SqlDataAdapter da = new SqlDataAdapter(sqlcomm))
                    {
                        da.Fill(dt);
                    }
                }
            }
            return dt;
        }
    }
}