嗯，谢啦，已经解决，
查询这边有一段，帮忙看看，有错，
public partial class Form3 : Form
{
public Form3(string str)
{
InitializeComponent();
this.id.Text = str;
SqlConnection Conn = new SqlConnection("Server=localhost;DataBase=学生成绩;Integrated Security =SSPI"); //建立数据库实例..
Conn.Open(); //打开数据库

SqlCommand Cmd = new SqlCommand();
Cmd.Connection = Conn;
Cmd.CommandType = CommandType.Text;
Cmd.CommandText = "select 姓名,语文,数学,英语 from 学生成绩 where 学号=str";
Cmd.ExecuteNonQuery(); //执行sql语句...
Conn.Close();
str是从Form1中传过来的学号

SqlConnection Conn = new SqlConnection("Server=localhost;DataBase=学生成绩;Integrated Security =SSPI"); //建立数据库实例..
string SelectStr = "select 姓名,语文,数学,英语 from 学生成绩 where 学号='" + str +"'" ;
Conn.Open(); //打开数据库
SqlCommand Cmd = new SqlCommand(SelectStr,Conn);
Cmd.ExecuteNonQuery(); //执行sql语句...
Conn.Close(); //关闭数据库


这样写比较好.呵呵

漏了东西，呵呵应该是这样
public partial class Form3 : Form
{
public Form3(string str)
{
InitializeComponent();
this.id.Text = str;
SqlConnection Conn = new SqlConnection("Server=localhost;DataBase=学生成绩管理系统;Integrated Security =SSPI"); //建立数据库实例..
Conn.Open(); //打开数据库

SqlCommand Cmd = new SqlCommand();
Cmd.Connection = Conn;
Cmd.CommandType = CommandType.Text;
Cmd.CommandText = "select 姓名,语文,数学,英语 from 学生成绩 where 学号=str";
Cmd.ExecuteNonQuery(); //执行sql语句...
SqlDataReader Myread = Cmd.ExecuteReader();
Myread.Read();
this.name.Text = Myread.GetString(1);
this.id.Text = Myread.GetValue(0).ToString();
this.chinese.Text = Myread.GetValue(2).ToString();
this.math.Text = Myread.GetValue(3).ToString();
this.english.Text = Myread.GetValue(4).ToString();
Conn.Close();
}