asp.net c#, session variable

The following code at line 3 produces an error.

if (HttpContext.Current.Session.ContainsKey("MySettings"))

Question: How can I correct my code?

Error: 'System.Web.SessionState.HttpSessionState' does not contain a definition for 'ContainsKey' and no extension method 'ContainsKey' accepting a first argument of type 'System.Web.SessionState.HttpSessionState' could be found (are you missing a using directive or an assembly reference?)  
Dictionary<string, string> settings = new Dictionary<string, string>();

 protected void Page_Load(object sender, EventArgs e)
{
            if (HttpContext.Current.Session.ContainsKey("MySettings"))
        {
            //HttpContext.Current.Session.Add("MySettings", settings);  // this line used elsewhere

            // store back settngs from last session
            settings = HttpContext.Current.Session["MySettings"] as Dictionary<string, string>;
        }
        else
        {
            upsdateSettings(listBoxes, "initialize"); // settings object gets initialized
        }

        if (IsPostBack)

        {
 
        }
        else
        {

        }
    }

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FYI, I have located part of this code on the web. The declaration was like:

Dictionary<string, List<int>> settings = new Dictionary<string, List<int>>();

Could be this why I am getting this error? I have changed List<int> to string.
LVL 34
Mike EghtebasDatabase and Application DeveloperAsked:
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Miguel OzSoftware EngineerCommented:
You need to check the key existence by comparing to null.
In code above replace:
if (HttpContext.Current.Session.ContainsKey("MySettings"))
with:
if (HttpContext.Current.Session["MySettings"] != null)
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Mike EghtebasDatabase and Application DeveloperAuthor Commented:
Hi Miguel,

This is the code to initialize settings (seems it is working ok):
  
private void upsdateSettings(Dictionary<string, bool> listBoxes, string intilaizeOrSessionVariables)
 {
         //FYI,  intilaizeOrSessionVariables is not used, will be deleted.

        settings.Clear();   //??? is this necessary

        foreach (string box in (from listBox in listBoxes where listBox.Value select listBox.Key))
        {
            ListBox lb = new ListBox() { ID = "lst" + box };
            settings.Add(box.ToString(), "-All-");
        }
}

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Question: Could you please check my syntax to store settings in the session variable and restore it from the session variable below:

To store:
HttpContext.Current.Session.Add("MySettings", settings);

Why I couldn't use just: Session.Add("MySettings")=settings;

To restore:
settings = HttpContext.Current.Session["MySettings"] as Dictionary<string, string>

or: settings = Session["MySettings"];
0
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