Question

ASP.NET中如何将SQL查询的值赋予一个label

using System;
using System.Collections;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
using System.Data.SqlClient;

namespace crmDD
{
public partial class _Default : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
string str = "server='(local)';database='crm';uid='sa';pwd=";
SqlConnection con = new SqlConnection(str);
con.Open();
string cw = "select Cpdj from cp where CpID = '+TextBox1.Text+'";
SqlCommand cmd = new SqlCommand(cw,con);
Label3.Text = cmd.ExecuteScalar().ToString();
con.Close();

}
}
}

Answer 1

DataTable dt=new DataTable();
SqlConnection myconn=new SqlConnection("server=服务器;uid=数据库用户;pwd=数据库密码;database=数据库");
myconn.Open();
string sql="select * from userIn";
Sqlcommand mycom=new Sqlcommand(sql,myconn);
mycom.Fill(dt);
myconn.Close();
//至此所有查询出来的数据放入了datatable里，现在随便你对datatable操作了
，如取第一行的所有列数据连接起来赋给一个string变量x:
string x="";
for(int i=0;i<dt.Rows.Count;i++)
{
x=x+dt.Rows[0][i].ToString();//第一行的第i列
}

Answer 2

建议用：
string cw =string.Format("select Cpdj from cp where CpID = '{0}'",TextBox1.Text);
可以养成一个编程好习惯，如果可能尽可能不要用带''符号，最容易被黑客注入。

Answer 3

string cw = "select Cpdj from cp where CpID = '+TextBox1.Text+'";
断点加在这句上，看看TextBox1.Text取到值没
然后继续往下走，看看各个变量有没有值

Answer 4

string cw = "select Cpdj from cp where CpID = '+TextBox1.Text+'";这句话有问题。
string cw = "select Cpdj from cp where CpID = '“+TextBox1.Text+”'";
或者使用string.format更容易控制：
string cw =string.Format("select Cpdj from cp where CpID = '{0}'",TextBox1.Text);

Answer 5

string str = "server='(local)';database='crm';uid='sa';pwd=";
SqlConnection con = new SqlConnection(str);
con.Open();
string cw = "select Cpdj from cp where CpID = '+TextBox1.Text+'";
SqlCommand cmd = new SqlCommand(cw,con);
//===================================
SqlDataReader rd;
rd = sqlcmd.ExecuteReader();
if (rd.Read())
{
Label3.Text = rd[0].ToString();
}
//==================================
con.Close();