嵌入SQL语句

嵌入SQL语言:
我将一个sql链接到数据库，该数据库名为master(系统数据库)
then 给数据库添加新表，建立三个key：userid(int),name(char(10)),password(char(10))
在窗体中弄三个textbox控件，分别定义Name属性为userid,name,password;
再来一个button
以下是Form1.cs中的代码
 using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Data.OleDb;
using System.Windows.Forms;
using System.Data.SqlClient;
using System.Runtime.InteropServices;
using System.Configuration;
namespace Str
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void submit_Click(object sender, EventArgs e)
{
/*
* connect to Sql Server
* 方法一：写在这里
*/
//string strConnection = "Data Source=ZRQ-PC;";
//strConnection += "Initial Catalog=master;Integrated Security=True";
// SqlConnection objConnection = new SqlConnection(strConnection);
/*
* 方法二：
* 这个方法为工程添加了新建项“应用程序配置文件”
* 将上面的那段写在App.config里
*/
string strConnection = ConfigurationSettings.AppSettings["connectionstring"];
SqlConnection objConnection = new SqlConnection(strConnection);
/************************************************************************/
if (name.Text == "")
MessageBox.Show("请输入姓名!", "提示", 0);
else
{
objConnection.Open();
SqlCommand cmd = new SqlCommand("select * from judging where userid='" + userid.Text.Trim() + "'", objConnection);
/*
***********************************************************************************************