SQLHelper 工具类的使用

新建一个winfrom窗体应用程序，为程序添加配置文件App.config，然后在配置文件中添加数据库连接字符串

<connectionStrings>
<add name ="constr" connectionString="server=PC-20171113RBMO;database=StudentDB;Trusted_Connection = True"/>
</connectionStrings>

 

　　

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

/// <summary>
/// SQLHelper 的摘要说明
/// </summary>
public class SQLHelper
{
    public SQLHelper()
    {
        //
        // TODO: 在此处添加构造函数逻辑
        //
    }
    //在程序中引用连接字符串
    static string str = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
    public static object ExecuteScalar(string sql, params SqlParameter[] paras)
    {

        //返回第一行第一列
        SqlConnection con = new SqlConnection(str);
        con.Open();
        SqlCommand cmd = new SqlCommand(sql, con);
        if (paras != null)
        {
            cmd.Parameters.AddRange(paras);
        }
        object o = cmd.ExecuteScalar();
        con.Close();
        return o;
    }

    public static DataTable ExecuteDataTable(string sql, params SqlParameter[] paras)
    {

        //查询
        SqlConnection con = new SqlConnection(str);
        con.Open();
        SqlCommand cmd = new SqlCommand(sql, con);
        if (paras != null)
        {
            cmd.Parameters.AddRange(paras);
        }
        SqlDataAdapter da = new SqlDataAdapter(cmd);
        DataTable dt = new DataTable();
        da.Fill(dt);
        con.Close();
        return dt;
    }

    public static int NonExQuery(string sql, params SqlParameter[] paras)
    {

        //增删改

        SqlConnection con = new SqlConnection(str);
        con.Open();
        SqlCommand cmd = new SqlCommand(sql, con);

        if (paras != null)
        {
            cmd.Parameters.AddRange(paras);
        }
        int i = cmd.ExecuteNonQuery();
        con.Close();
        return i;

    }

    public static SqlDataReader ExecReader(string sql, params SqlParameter[] paras)
    {
        
        SqlConnection con = new SqlConnection(str);
        con.Open();
        SqlCommand cmd = new SqlCommand(sql, con);

        if (paras != null)
        {
            cmd.Parameters.AddRange(paras);
        }
        SqlDataReader dr = cmd.ExecuteReader();
        con.Close();
        return dr;

    }
}