C#中 sqlDataRead 的三种方式遍历读取各个字段数值

Posted 2021-01-03 simple-article

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数据库的查询分析器中写上如下代码：

ccreate table studentname
(
 id  int   primary key  identity(1,1) not null ,
name nvarchar(500) not null
)

insert into studentname values(‘long‘)

insert into studentname values(‘long‘)

insert into studentname values(‘long‘)

insert into studentname values(‘long‘)

insert into studentname values(‘long‘)

insert into studentname values(‘chao‘)

insert into studentname values(‘chao‘)

--sql server 2012 通过。

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以下是第一种方法：

using System.Data;

 using System.Data.SqlClient;

string constr = "server=localhost;uid=sa;pwd=longshicheng;database=Student";

            SqlConnection conn = new SqlConnection(constr);

            SqlCommand cmd = new SqlCommand("select * from studentname", conn);

            conn.Open();

            SqlDataReader rdr = cmd.ExecuteReader();
            string makestr = "";
            DataTable table = new DataTable();
            table.Load(rdr);  //数据表装入 dataReader 。
            string result="";
            for (int i = 0; i < table.Rows.Count; i++) // 遍历行
            {
                for (int j = 0; j < table.Columns.Count; j++) //遍历列
                {
                    result += table.Rows[i][j].ToString(); //逐行逐列显示每个单元格的数值。
                }
                result += Environment.NewLine;  //一行遍历完成就写入回车。
            }
            txtlab.Text = result;

            /***************************************************************/

以下是第二种方法:

           string constr = "server=localhost;uid=sa;pwd=longshicheng;database=Student";

            SqlConnection conn = new SqlConnection(constr);

            SqlCommand cmd = new SqlCommand("select * from studentname", conn);

            conn.Open();

            SqlDataReader rdr = cmd.ExecuteReader();
            string makestr = "";
            for (int k = 0; k < rdr.FieldCount; k++) //获取字段名称
            {
                makestr += rdr.GetName(k) + "\t";  //载入字段名称
            }
            makestr += Environment.NewLine;  //换行
            makestr = makestr + "---------------------------------------------"+Environment.NewLine;
            while (rdr.Read())  //逐行读取每一笔记录
            {
                for (int t = 0; t < rdr.FieldCount; t++)  //逐列读出
                {
                    makestr = makestr + rdr[t].ToString() + "\t"; //累加每一行，也就是逐个字段读出对应的数值
                }
                makestr = makestr + Environment.NewLine; //又一行
            }
            txtinfo.Text = makestr;
            rdr.Close(); //关闭
            conn.Close();
        }

以下是第三种方法：

string constr = "server=localhost;uid=sa;pwd=longshicheng;database=Student";

            SqlConnection conn = new SqlConnection(constr);

            SqlCommand cmd = new SqlCommand("select * from studentname", conn);

            conn.Open();

            SqlDataReader rdr = cmd.ExecuteReader();
            string makestr = "";
             
            for (int k = 0; k < rdr.FieldCount; k++) //获取字段名称
            {
                makestr += rdr.GetName(k) + "\t";  //载入字段名称
            }
            makestr += Environment.NewLine;  //换行
            makestr = makestr + "---------------------------------------------" + Environment.NewLine;
            while (rdr.Read())  //逐行读取每一笔记录
            {
                makestr = makestr + rdr.GetValue(0) + " \t" + rdr.GetValue(1).ToString() + "\t";
                makestr = makestr + Environment.NewLine;
            }
            txtother.Text = makestr;
            rdr.Close(); //关闭
            conn.Close();

以上所有方法运行结果均如下：

id    name    
---------------------------------------------
1     long  
2     long    
3     long    
4     long     
5     long     
6     chao    
7     chao