C#初学者小问题求解

Question

            if (TextBox1.Text != "" && TextBox2.Text != "")
            {
                string username = "'" + TextBox1.Text.Trim().ToString() + "'";
                string pwd = "'" + TextBox2.Text.Trim().ToString() + "'";
                SqlConnection conn = new SqlConnection(System.Configuration.ConfigurationManager.AppSettings["conn"]);
                conn.Open();
                SqlCommand cmd = new SqlCommand("select * from users where username=" + username + " and stuid=" + pwd, conn);
                cmd.ExecuteReader();
            }
做的一个登陆系统，写到判断用户名是否有数据不知怎么写了，由于我是ASP转来学的，对C#对象不了解，不知道C#的记录集对象也不知如何判断表里是否有数据，ASP的记录集对象RECORDSET也就一个，C#好像有N个，弄迷糊了。
第一，请大侠帮我完成上面，判断有没有该用户名在表里，如果有怎么获取用户名信息。
第二，说下C#有几个记录集对象，继然有几个，肯定都有各自的用途，请详解一下，谢谢！（注册不久没什么分多多包含）

Answer 1

using System;
using System.Collections.Generic;
using System.Text;
using System.Data;
using System.Data.SqlClient;
using System.Configuration;//
namespace CSDNDAL.DBConnection
{
    public class DBBase
    {
            #region 声明的变量
        protected SqlConnection obj_Con=null;
        protected SqlCommand obj_Cmd = null;
        protected SqlDataReader obj_Dr;
        protected bool flage = false;
        private static string constring = ConfigurationManager.ConnectionStrings["Connectionstring"].ToString();
        #endregion
        #region 打开连接对象
        public SqlConnection CreateSqlConnection() 
        {
            try
            {
                //QINGNIAO-JF6002\\ACCP
                this.obj_Con = new SqlConnection(constring);
                this.obj_Con.Open();
            }
            catch(Exception ex)
            {
                ex.ToString();
            }
            return this.obj_Con;
        }
        #endregion
        #region 关闭数据库连接
        /// <summary>
        /// 关闭数据库连接
        /// </summary>
        /// <param name="objCon">SqlConnection对象</param>
        public void CloseSqlConnection(SqlConnection objCon) 
        {
            try
            {
                if (objCon != null)
                    objCon.Close();
                this.obj_Con = null;
            }
            catch (Exception ex) 
            {
                ex.ToString();
            }
        }
        #endregion 
        #region 检验登录是否存在
        /// <summary>
        /// 检验用户登录
        /// </summary>
        /// <param name="sql">sql语句</param>
        /// <returns>bool值</returns>
        public bool Exists_DB(string sql) 
        {
            try
            {
                this.obj_Con = this.CreateSqlConnection();
                this.obj_Cmd = new SqlCommand(sql, this.obj_Con);
                this.obj_Dr = this.obj_Cmd.ExecuteReader();
                if (this.obj_Dr.Read())
                {
                    flage = true;
                }
                else 
                {
                    flage = false;
                }
            }
            catch (Exception ce)
            {
                ce.ToString();
            }
            finally 
            {
                this.CloseSqlConnection(this.obj_Con);
            
            }
            return flage;        }
        #endregion
        #region 对数据库的一些操作
        public bool Update_DB(string sql) 
        {
            try
            {
                this.obj_Con = this.CreateSqlConnection();
                this.obj_Cmd = new SqlCommand(sql, this.obj_Con);
                int num = this.obj_Cmd.ExecuteNonQuery();
                if (num > 0)
                    flage = true;
                else
                    flage = false;            }
            catch (Exception ce)
            {
                ce.ToString();
            }
            finally 
            {
                this.CloseSqlConnection(this.obj_Con);
            }
            return flage;
        
        }
        /// <summary>
        /// 根据查询语句和SqlParameter单一的值来返回一个DataTable
        /// </summary>
        /// <param name="dataSql">sql语句</param>
        /// <param name="value">参数</param>
        /// SqlParameter[] paras = new SqlParameter[] { 
        ///                                            new SqlParameter("@id",id,类型),
        ///                                            new SqlParameter("@pwd",pwd，类型)
        ///                                            };                       
        /// <returns>DataTable</returns>
        public  DataTable GetDataTable(string dataSql, SqlParameter[] values)
        {
            this.obj_Con = this.CreateSqlConnection();
            DataSet ds = new DataSet();
            SqlCommand command = new SqlCommand(dataSql, this.obj_Con);
            command.Parameters.AddRange(values);
            SqlDataAdapter sqlAda = new SqlDataAdapter(command);
            sqlAda.Fill(ds);
            return ds.Tables[0];
        }        public DataSet GetDataDataset(string dataSql)
        {
            this.obj_Con = this.CreateSqlConnection();
            DataSet ds = new DataSet();
            this.obj_Cmd = new SqlCommand(dataSql, this.obj_Con);
            SqlDataAdapter sqlAda = new SqlDataAdapter(this.obj_Cmd);
            sqlAda.Fill(ds);
            return ds;
        }
        /// <summary>
        /// 返回的DataTable，没有参数
        /// </summary>
        /// 取值
        /// foreach(dataRow ds in DataTable.row)
        /// {
        ///   module ss = new module;
        ///   ss.name = ds[""].toString();
        ///   this.list.add(ss);
        /// }
        /// 
        /// <param name="dataSql">查询语句</param>
        /// <returns>DataTable</returns>
        public  DataTable GetDataTable(string dataSql)
        {
            this.obj_Con = this.CreateSqlConnection();
            DataSet ds = new DataSet();
            this.obj_Cmd = new SqlCommand(dataSql, this.obj_Con);
            SqlDataAdapter sqlAda = new SqlDataAdapter(this.obj_Cmd);
            sqlAda.Fill(ds);
            return ds.Tables[0];
        }
        /// <summary>
        ///  返回结果集
        /// </summary>
        /// <param name="dataSql"></param>
        /// <returns></returns>
        public  SqlDataReader ExecuteReader(string dataSql)
        {
            this.obj_Con = this.CreateSqlConnection();
            SqlCommand command = new SqlCommand(dataSql, this.obj_Con);
            SqlDataReader reader = command.ExecuteReader();
            return reader;
        }
        /// <summary>
        /// 返回单行的数据
        /// </summary>
        /// <param name="dataSql">sql语句</param>
        /// <param name="values">值</param>
        /// <returns>string类型的值</returns>
        public string GetExecuteScalar(string dataSql, SqlParameter[] values)
        {
            this.obj_Con = this.CreateSqlConnection();
            this.obj_Cmd = new SqlCommand(dataSql, this.obj_Con);
            this.obj_Cmd.Parameters.AddRange(values);
            return this.obj_Cmd.ExecuteScalar().ToString();
        }
        /// <summary>
        /// 返回单行数据
        /// </summary>
        /// <param name="dataSql">sql语句</param>
        /// <param name="value">参数</param>
        /// <returns>单个的数据</returns>
        public string GetExecuteScalar(string dataSql)
        {
            this.obj_Con = this.CreateSqlConnection();
            this.obj_Cmd = new SqlCommand(dataSql, this.obj_Con);
            return this.obj_Cmd.ExecuteScalar().ToString();
        
        }
        #endregion
        #region 对数据库存储过程的一些操作        public string GetExecuteScalar(string dataSql,CommandType type,SqlParameter[] values)
        {
            try
            {
                this.obj_Con = this.CreateSqlConnection();
                this.obj_Cmd = new SqlCommand(dataSql, this.obj_Con);
                this.obj_Cmd.CommandType = type;
                this.obj_Cmd.Parameters.AddRange(values);
                return this.obj_Cmd.ExecuteScalar().ToString();
            }
            catch { }
            finally 
            {
                this.CloseSqlConnection(obj_Con);
            
            }
            return "-1";
        }        #endregion     }
}

Answer 2

不要急，慢慢来，有空教我玩ASP啊。

Answer 3

有没有搞错这样个小功能这么多代码，我试都不用试了，ASP里2行就判断好了。

Answer 4

bloo temp = false;
if (TextBox1.Text != "" && TextBox2.Text != "") 
{ 
    string username = "'" + TextBox1.Text.Trim().ToString() + "'"; 
    string pwd = "'" + TextBox2.Text.Trim().ToString() + "'"; 
    SqlConnection conn = new SqlConnection(System.Configuration.ConfigurationManager.AppSettings["conn"]); 
    conn.Open(); 
    SqlCommand cmd = new SqlCommand("select * from users where username=" + username + " and stuid=" + pwd, conn); 
    SqlDataReader reader = cmd.ExecuteReader(); 
    if(reader.Read())
    {
        temp = true;
    }
} 
这样如何0 0...查到数据就进入if里把那temp变为true代表查到数据……
或者你声明个实体类也行，在Read()的if里把它new出来，读出数据就是有值否则实体类就为null

Answer 5

那个事别个给你的数据库操作类。告诉你ado.net怎么用。