Cached dropdownlist not consistent

Ive got a basic aspx page that loads a dropdown with employee names.  Since this data rarely changes, and since its around 6,000 names, I decided to cache the data using the code in the snippet.  My problem is that sometimes the dropdown has data..and sometimes it doesnt.  If I start a debug session and the dropdown is not filled, I can usually wait a minute or two then start the debugger back up and it will then be filled.  Why would it sometimes have data and other times be empty?  
if (Cache["employees"] == null)
                DataTable dt = new DataTable();
                dt = employees.GetEmployees();
                Cache.Insert("employees", dt, null, DateTime.Now.AddMinutes(480), TimeSpan.Zero);
            ddlEmployee.DataSource = (DataTable)Cache.Get("employees");
            ddlEmployee.DataTextField = "name";
            ddlEmployee.DataValueField = "emplid";

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David H.H.LeeCommented:
Hi clintfield,
May i know why you need to cache the data before output the resouces? It's not adviceable to use Cache in somehow. Please refer following articles for more details regarding Cache usage. Please check if you really need to use Cache in the existing code:
You may need to check why Cache object display inconsistenly for some reason:
Caching time and expiration:

clintfieldAuthor Commented:
I could rewrite the code to supply the dropdown and then cache.  The real problem is that the dropdown sometimes doesnt have any data, even though it should have been cached.  I cached this particular dropdown because it contains a massive amount of names (I rechecked and there are actually 40,000+ names!) and it rarely changes.  It is also called regularly and sometimes more than once on the same page.
David H.H.LeeCommented:
Hi clintfield,
That is too huge data for dropdownlist's resource. Perhaps you can try with other way instead of bind too large data in the dropdownlist. You can try use an AutoCompleteExtender instead.
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clintfieldAuthor Commented:
That looks sweet....but my company hasnt certified the toolkit yet so I cant use that.  ;-(
David H.H.LeeCommented:
Hi clintfield,
Then you can let them know how good it is compare with old solution. There are a lot of useful controls available for AJAX toolkit:
Good luck to your project.


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clintfieldAuthor Commented:
Thanks for the ideas.
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