protected void Page_Load(object sender, EventArgs e)
    {
        this.aa();
    }
    public void aa()
    {
        SqlConnection con = new SqlConnection();
        con.ConnectionString = "server=(local);uid=sa;pwd=;database=stu;";
        SqlCommand cmd = new SqlCommand();
        cmd.CommandText = "select * from student";
        cmd.Connection = con;
        SqlDataAdapter sda = new SqlDataAdapter();
        sda.SelectCommand = cmd;
        con.Open();
        DataSet ds = new DataSet();
        sda.Fill(ds, "student");
        con.Close();
        this.GridView1.DataSource = ds;
        this.GridView1.DataBind();
    }

protected void Button1_Click(object sender, EventArgs e)
    {
        ///这是插入
        if (this.TextBox1.Text == "" && this.TextBox2.Text == "" && this.TextBox3.Text == "")
        {
            Response.Write("<script language=javascript>alert('信息不能为空,请必须全部填写！')</script>");
        }
        else
        {
            SqlConnection con = new SqlConnection();
            con.ConnectionString = "server=(local);uid=sa;pwd=;database=stu;";
            SqlCommand cmd = new SqlCommand();
            cmd.CommandText = "insert into student values(" + this.TextBox1.Text + ",'" + this.TextBox2.Text + "','" + this.TextBox3.Text + "')";
            cmd.Connection = con;
            con.Open();
            cmd.ExecuteNonQuery();
            con.Close();
        }
       
    }
    protected void Button4_Click(object sender, EventArgs e)
   {
        ///这是刷新
       //this.aa();
       SqlConnection con = new SqlConnection();
       con.ConnectionString = "server=(local);uid=sa;pwd=;database=stu;";
       SqlCommand cmd = new SqlCommand();
       cmd.CommandText = "select * from student";
       cmd.Connection = con;
       con.Open();
    }

///偶的疑问是为啥Button4_Click中没有使用 datasource,databind,也没有调用page_load里面的aa,却能够刷新gridview1?
只是打开了一个连接，就能刷新gridview1?????
为啥同样执行Button1_Click，却不能刷新gridview1????非要再执行Button4_Click才行？？？？？？