求大神回复
protected void Page_Load(object sender, EventArgs e)
  {
  getdata();
  }
  //获取数据绑定在GV1上
  private void getdata()
  {
  DataClassesDataContext db = new DataClassesDataContext(); //数据源
  var query = from a in db.stu_mark select new { a.ID, a.mark,a.name,a.number,a.course,a.credit }; //创建查询，将两个表关联起来查询
  GridView1.DataSource = query;//执行查询，将数据显示在GV1
  GridView1.DataBind();
  }
   
  protected void Button1_Click(object sender, EventArgs e)
  {
  DataClassesDataContext ctx = new DataClassesDataContext();
  List<stu_mark> contents = new List<stu_mark>();

  contents = ctx.stu_mark.ToList();
  GridView1.DataSource = contents;
  GridView1.DataBind();  

  stu_mark one = new stu_mark();
  one.name = TextBox1.Text;
  one.number = TextBox2.Text;
  one.course = TextBox3.Text;
  one.credit = TextBox4.Text;
  one.mark = TextBox5.Text;

  ctx.stu_mark.InsertOnSubmit(one);
  ctx.SubmitChanges();
   
  }
   
  protected void GridView1_RowDeleting1(object sender, GridViewDeleteEventArgs e)
  {
  string strID = GridView1.DataKeys[e.RowIndex].Value.ToString();
  int intstrID = Convert.ToInt32(strID);

  DataClassesDataContext ctx = new DataClassesDataContext();//数据源
  var query = from a in ctx.stu_mark
  where a.ID == intstrID
  select a;
  ctx.stu_mark.DeleteAllOnSubmit(query);//删除
  ctx.SubmitChanges();//更新
  }
  protected void Button2_Click(object sender, EventArgs e)
  {
  Response.Redirect("Login.aspx");
  Response.End();
  }
}
为什么删两次才能在表中删除，添加的时候也是，第一次添加的时候数据库中就已经加上了，但是表中不显示，第二次添加表里才显示

------解决方案--------------------
protected void Page_Load(object sender, EventArgs e)
{
if(!IsPostBack)
{
getdata();
}
}
//获取数据绑定在GV1上
private void getdata()
{
DataClassesDataContext db = new DataClassesDataContext(); //数据源
var query = from a in db.stu_mark select new { a.ID, a.mark,a.name,a.number,a.course,a.credit }; //创建查询，将两个表关联起来查询
GridView1.DataSource = query;//执行查询，将数据显示在GV1
GridView1.DataBind();
}

protected void Button1_Click(object sender, EventArgs e)
{
DataClassesDataContext ctx = new DataClassesDataContext();
List<stu_mark> contents = new List<stu_mark>();

contents = ctx.stu_mark.ToList();
GridView1.DataSource = contents;
GridView1.DataBind();

stu_mark one = new stu_mark();
one.name = TextBox1.Text;
one.number = TextBox2.Text;
one.course = TextBox3.Text;
one.credit = TextBox4.Text;
one.mark = TextBox5.Text;

ctx.stu_mark.InsertOnSubmit(one);
ctx.SubmitChanges();
getdata();
}

protected void GridView1_RowDeleting1(object sender, GridViewDeleteEventArgs e)
{
string strID = GridView1.DataKeys[e.RowIndex].Value.ToString();
int intstrID = Convert.ToInt32(strID);

DataClassesDataContext ctx = new DataClassesDataContext();//数据源
var query = from a in ctx.stu_mark
where a.ID == intstrID
select a;
ctx.stu_mark.DeleteAllOnSubmit(query);//删除
ctx.Su