LINQ Specified Cast Not Valid - asp.net

Question

Not getting much info on this error, but I'm not using any casting in this specific code, so I'm pretty lost.
var dsn = Request.ServerVariables["HTTP_HOST"].Split('.').First();
using (var ctx = new SharedDataContext("switchcurrent"))
{
var dbDsn = ctx.SiteObjects.FirstOrDefault(s => s.DSN == dsn);
if (dbDsn == null)
{
Session["CurrentDsn"] = "SwitchCurrent";
}
else
{
Session["CurrentDsn"] = dbDsn.DSN;
Response.Redirect(String.Format("~/{0}", dbDsn.DefaultPage));
}
}
The LINQ statement is where I'm getting the error. If the statement returns null, the code continues fine, but if it's an actual match with an object in the database, I'm getting this error.
EDIT (additional info)
The error message is an InvalidCastException
Stack trace:
at System.Data.Linq.SqlClient.SqlProvider.Execute(Expression query, QueryInfo queryInfo, IObjectReaderFactory factory, Object[] parentArgs, Object[] userArgs, ICompiledSubQuery[] subQueries, Object lastResult)at System.Data.Linq.SqlClient.SqlProvider.ExecuteAll(Expression query, QueryInfo[] queryInfos, IObjectReaderFactory factory, Object[] userArguments, ICompiledSubQuery[] subQueries) at System.Data.Linq.SqlClient.SqlProvider.System.Data.Linq.Provider.IProvider.Execute(Expression query)at System.Data.Linq.Table`1.System.Linq.IQueryProvider.Execute[TResult](Expression expression)at System.Linq.Queryable.FirstOrDefault[TSource](IQueryable`1 source, Expression`1 predicate) at WebApplication1.Default.SetCurrentDsn() in C:\Code\dir\Default.aspx.cs:line 163 at WebApplication1.Default.Page_Load(Object sender, EventArgs e) in C:\Code\dir\Default.aspx.cs:line 32 at System.Web.Util.CalliHelper.EventArgFunctionCaller(IntPtr fp, Object o, Object t, EventArgs e) at System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object sender, EventArgs e) at System.Web.UI.Control.OnLoad(EventArgs e) at System.Web.UI.Control.LoadRecursive() at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)
SiteObject.Dsn is a string. and so is dsn.
Basically if it is 'localhost' (which isn't in the db) the code passes, but if its a match ('pgande') this error is thrown.

Answer 1

If s.DSN cannot be cast to dsn, you'll get this error. You may need to supply a conversion.

Answer 2

I think you already tried, but may be you need to cast dsn, not s.DSN? Try something link "s => s.DSN == dsn.ToString()".
Did this help?

Answer 3

Try this:
var dbDsn = ctx.SiteObjects.FirstOrDefault(s => s.DSN.ToString() == dsn.ToString());

Answer 4

I ended up dropping the table back into my Data Context and everything is working. Obviously something was corrupt with the table that was dropped in there the first time.