C# SqlHelper应用开发学习

封装一个SQLHelper类方便使用

using System.Configuration;
using System.Data;//DatSet..Table SqlDataAdapter
using System.Data.SqlClient;//SqlConnection Command DataReader
namespace Common
{
 public class SqlHelper
 {
 //连接字符串
 //1、添加引用 2、导入命名空间 为了使用ConfigurationManager
 private static string conStr = ConfigurationManager.ConnectionStrings["conStr"].ConnectionString;

 //增删改查
 //查找数据 ExecuteScalar()返回首行首列 ExecuteReader() DataTable


 /// <summary>
 /// 返回DataTable
 /// </summary>
 /// <param name="sql">所用的sql语句</param>
 /// <param name="param">可变，可以传参也可以不传参数</param>
 /// <returns></returns>
 public static DataTable ExecuteDataTable(string sql, params SqlParameter[] param)
 {
 DataTable dt = new DataTable();
 using (SqlConnection con = new SqlConnection(conStr))
 {
 using (SqlDataAdapter adapter = new SqlDataAdapter(sql, con))
 { 
  //添加参数
  adapter.SelectCommand.Parameters.AddRange(param);
  //1.打开链接，如果连接没有打开，则它给你打开；如果打开，就算了
  //2.去执行sql语句，读取数据库
  //3.sqlDataReader,把读取到的数据填充到内存表中
  adapter.Fill(dt);
 }
 }
 return dt;
 }

 /// <summary>
 /// 执行查询，返回首行首列
 /// </summary>
 /// <param name="sql"></param>
 /// <param name="param"></param>
 /// <returns></returns>
 public static object ExecuteScalar(string sql, params SqlParameter[] param)
 {
 object o = null;
 using (SqlConnection con = new SqlConnection(conStr))
 {
 using (SqlCommand cmd = new SqlCommand(sql, con))
 {
  cmd.Parameters.AddRange(param);
  con.Open();

  o = cmd.ExecuteScalar();
 }
 }
 return o;
 }


 /// <summary>
 /// 执行查询，返回SqlDataReader对象
 /// </summary>
 /// <param name="sql"></param>
 /// <param name="param"></param>
 /// <returns></returns>
 public static SqlDataReader ExecuteReader(string sql, params SqlParameter[] param)
 {
 SqlDataReader reader = null;
 using (SqlConnection con = new SqlConnection(conStr))
 {
 using (SqlCommand cmd = new SqlCommand(sql, con))
 {
  cmd.Parameters.AddRange(param);
  con.Open();

  reader = cmd.ExecuteReader();
 }
 }
 return reader;
 }

 /// <summary>
 /// 执行增删改，返回受影响的行数
 /// </summary>
 /// <param name="sql"></param>
 /// <param name="param"></param>
 /// <returns></returns>
 public static int ExecuteNonQuery(string sql, params SqlParameter[] param)
 {
 int n = -1;
 using (SqlConnection con = new SqlConnection(conStr))
 {
 using (SqlCommand cmd = new SqlCommand(sql, con))
 {
  cmd.Parameters.AddRange(param);
  con.Open();
  n = cmd.ExecuteNonQuery();
 }
 }
 return n;
 }

 }
}								 
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