HttpContext.Current.Session unclear behaviour boolean

Question

I'm having a weird behaviour trying to get the value of a boolean property stored at HttpContext.Current.Session.

The object is a boolean. First I'm trying to check if the object exists and, if exists, use it.

I'm trying to use it in a ?: operator but it behaves strange. Here is my Watch window:

Premise

• The "ExistingKey" key exists and has a value of false (if key doesn't exists returns false).

Results

1. When checking if !=null it returns false (first thing weird).
2. When using the ?: operator, besides the condition is false, it returns the first expression, 4 (second thing weird).

Could somebody explain this behaviour?

---

Note: I'm not asking for an alternative to bypass this situation. Just asking why this works like this.

Answer 1

It seems to be some sort of bug within the watch window. I tested the following code:

protected void Page_Load(object sender, EventArgs e)
{
   var  objDict = new Dictionary<string, object>();
    var boolDict = new Dictionary<string, bool>();
    Session["ExistingValue"] = false;
    bool? nullableValue = false;

    Session["ExistingValueNullable"] = nullableValue;
    var existingValue = (bool)Session["ExistingValue"];
    var existingValueIsNotNull = Session["existingValue"] != null;
    objDict["ExistingValue"] = false;
    boolDict["ExistingValue"] = false;
    bool existingValueIsNotNullIf = false;
    if (Session["ExistingValue"] != null)
    {
        existingValueIsNotNullIf = true;
    }
}

And I got the following in the watch window:

So you can see that in the case of Session and a Dictionary<string,object> the != null evaluates to false. A Dictionary<string,bool> evaluates this comparison properly.

Weirdly, 'Session["ExistingValue"] != null' and 'Session["ExistingValue"]' == null' are both false.

If I cast the session value to a bool first then compare to null, I get the correct result.

Finally, if I test the value 'Session["ExistingValue"] != null' in code, I get a proper result. Which at least reassures me that this is something in the watch window, and there shouldn't be a similar issue in code.

All my testing was in Visual Studio 2015.

Answer 2

Please do not consider this an answer at the moment, the following is much easier to write in an answer than in a comment due to space and formatting constraints.

I agree with the comments on the question, line 3 is not consistent with the results of the other lines. The only thing I can think of that could explain this is that the Watch window in Visual Studio has stale data / has a corrupted state. I think executing the same statements but in the code itself could prove or refute this. The following code is the same as what you have but output to a StringBuilder. Could you execute this and post the resulting string and let us know if this is any different from what you have in your Watch window?

var session = HttpContext.Current.Session;
var builder = new System.Text.StringBuilder();

builder.AppendFormat("session[\"someKeyThatDoesNotExist\"] => value {0}", session["someKeyThatDoesNotExist"] ?? "null").AppendLine();
builder.AppendFormat("session[\"ExistingKey\"] => value {0}", session["ExistingKey"] ?? "null").AppendLine();
builder.AppendFormat("session[\"ExistingKey\"] != null => value {0}", session["ExistingKey"] != null).AppendLine();
builder.AppendFormat("session[\"ExistingKey\"] != null ? 4 : 5 => value {0}", session["ExistingKey"] != null ? 4 : 5).AppendLine();
builder.AppendFormat("session[\"ExistingKey\"] == null ? 4 : 5 => value {0}", session["ExistingKey"] == null ? 4 : 5).AppendLine();

var totalDebugInfo = builder.ToString();