Viewstate to keep data after postback

Question

[Personalizable(PersonalizationScope.Shared)]
    [WebPartStorage(Storage.Shared)]
        public List<searchResult> lsQtys
    {
      get
      {
          List<searchResult> lsQuantities = (List<searchResult>)ViewState["lsQuantities"];
          return lsQuantities;
      }
        set
        {
            ViewState["lsQuantities"] = value;
        }
    }

I build up this list of varaibles when the webpart is first rendered and using the immediate window i can see that the viewstate is storing the variables. However on the button press the information stored in the viewstate is then null? is there any reason why this information would be lost/unavailable on postback?

Answer 1

I think you want to take a look at this http://msdn.microsoft.com/en-us/library/ms178472.aspx

Explaining the ASP.Net lifecycle of a page. And here you can find where the ViewState values are added to the Viewstate collection on a postback.

Answer 2

use this property. this will work.

    [Personalizable(PersonalizationScope.Shared)]
    [WebPartStorage(Storage.Shared)]
    public string CacheF
    {
        get
        {
            if (!string.IsNullOrEmpty((string)ViewState["CacheF"]))
                return (string)ViewState["CacheF"];

            return !string.IsNullOrEmpty(Session["CacheF"]) ? Session["CacheF"] : string.Empty;
        }
        set => ViewState["CacheF"] = Session["CacheF"] = value;
    }