临时存储数据列表c＃

Question

So I have this problem with storing temporary data, basically the effect I'm after is something like this Link

My problem is when I do it on List or Binding list, it won't save the old rows and just change it to the new ones.

Here is the code I got

BindingList<Genrer> Film_Genrer = new BindingList<Genrer>(); 
Genrer genrer = new Genrer();
protected void Page_Load(object sender, EventArgs e)
{
    if (!IsPostBack)
    {
        DropDownList_Genrer.DataSource = Db.SelectAllFrom("Genrer");
        DropDownList_Genrer.DataTextField = "genrer_navn";
        DropDownList_Genrer.DataValueField = "genrer_id";
        DropDownList_Genrer.DataBind();
    }
}

protected void Button_AddGenrer_Click(object sender, EventArgs e)
{
    Genrer genrer = new Genrer();
    genrer.Navn = DropDownList_Genrer.SelectedValue;

    Film_Genrer.Add(genrer);
    GridView1.DataSource = Film_Genrer;
    GridView1.DataBind();
}

Answer 1

In the Button_AddGenrer_Click method, your Film_Genrer is initially empty and you just add one item to that and set it as DataSource. What you need to do is first add all your items to Film_Genrer , then add the new item and then set the DataSource.