Question

I’m getting this error, not really sure why. Please help, this is urgent.

UPDATE

if (flights.Count() >= 1)
        {
            int count = flights.Count();
            lblNumResults.Text = count.ToString();
            gvAvailableFlights.DataSource = flights;
            gvAvailableFlights.DataBind();
        }

Server Error in ‘/WebSite3’
Application. Value cannot be null.
Parameter name: element Description:
An unhandled exception occurred during
the execution of the current web
request. Please review the stack trace
for more information about the error
and where it originated in the code.

Exception Details:
System.ArgumentNullException: Value
cannot be null. Parameter name:
element

Source Error:

The source code that generated this
unhandled exception can only be shown
when compiled in debug mode. To enable
this, please follow one of the below
steps, then request the URL:

1. Add a “Debug=true” directive at the top of the file that generated the
   error. Example:

   <%@ Page Language=”C#” Debug=”true”
   %>

or:

2) Add the following section to the
configuration file of your
application:

Note that this second technique will
cause all files within a given
application to be compiled in debug
mode. The first technique will cause
only that particular file to be
compiled in debug mode.

Important: Running applications in
debug mode does incur a
memory/performance overhead. You
should make sure that an application
has debugging disabled before
deploying into production scenario.

Stack Trace:

[ArgumentNullException: Value cannot
be null. Parameter name: element]
System.Xml.Linq.XElement.op_Explicit(XElement
element) +116474
searchresult.b__1d(XElement
f) +64
System.Linq.WhereSelectEnumerableIterator2.MoveNext()
+151 System.Linq.Enumerable.Count(IEnumerable1
source) +201
searchresult.FillAvailableFlightsGridView()
+721 searchresult.Page_Load(Object sender, EventArgs e) +37
System.Web.Util.CalliHelper.EventArgFunctionCaller(IntPtr
fp, Object o, Object t, EventArgs e)
+14 System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object
sender, EventArgs e) +35
System.Web.UI.Control.OnLoad(EventArgs
e) +91
System.Web.UI.Control.LoadRecursive()
+74 System.Web.UI.Page.ProcessRequestMain(Boolean
includeStagesBeforeAsyncPoint, Boolean
includeStagesAfterAsyncPoint) +2207

Version Information: Microsoft .NET
Framework Version:4.0.30319; ASP.NET
Version:4.0.30319.1

Answer 1

In your code you have function called FillAvailableFlightsGridView and in that function you call Count() of some collection which is null.

Before calling the Count() check if it’s null and in such case, assume zero length or do whatever handling you want.

For example:

int myCount = 0;
if (myCollection != null)
   myCount = myCollection.Count();

Edit: optimized code in your case would be:

int flightsCount = (flights == null) ? 0 : flights.Count();
if (flightsCount >= 1)
{
    lblNumResults.Text = flightsCount.ToString();
    gvAvailableFlights.DataSource = flights;
    gvAvailableFlights.DataBind();
}

No need to call Count() twice, as you saw it contains internal code that might be heavy.