How to store record using ViewState

问题

Now there are 2 buttons, let's call them "Button1" and "Button2" respectively. If I click "Button1", store "1" in ViewState["Record"]; also, if I click "Button2", store "2" in ViewState["Record"], etc.

When I click Button1⟶Button1⟶Button2⟶Button2, my expected result is: in ViewState["Record"], there are a list of records, like

[1,1,2,2].

Here is my click event code:

protected void Button1_Click(object sender, EventArgs e)
{
  ViewState.Add("Record", "1");
}
protected void Button2_Click(object sender, EventArgs e)
{
  ViewState.Add("Record", "2");
}
//show the viewstate result
protected void ShowResult(object sender, EventArgs e)
{
 for (int i = 1; i <= 4; i++)
    {
       Label.Text += ViewState["Record"];
    }
}

It shows "2222" instead of "1122". How can I code to resolve it?

回答1:

When you add Record key a value actually it not adds, just puts a value Record key. You always see last added value on your loop.

You should add a List to ViewState and add value to list.

Add this property

protected  List<long> ViewStateList
{
  get{ if(ViewState["Record"] == null) ViewState["Record"] = new  List<long>(); 
       return (List<long>)ViewState["Record"]  }
}

And use like

protected void Button1_Click(object sender, EventArgs e)
{
  ViewStateList.Add(1);
}

Loop

protected void ShowResult(object sender, EventArgs e)
{
 foreach(long item in ViewStateList)
    {
       Label.Text += item.ToString();
    }
}

来源：https://stackoverflow.com/questions/10257607/how-to-store-record-using-viewstate