Radimir:
Выяснил что (ConfigurationSettings.AppSettings["connectionString"]); есть null  почему не приходит значение connectionString?
Наверное его нет в web.config----------------------------------------
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ММММ.... ДА...
static void ShowConnectionStrings()
{
// Get the application configuration file.
System.Configuration.Configuration config =
ConfigurationManager.OpenExeConfiguration(
ConfigurationUserLevel.None);

// Get the conectionStrings section.
ConnectionStringsSection csSection =
config.ConnectionStrings;

for (int i = 0; i ConfigurationManager.ConnectionStrings.Count; i++)
{
ConnectionStringSettings cs =
csSection.ConnectionStrings[i];

Console.WriteLine(" Connection String: \"{0}\"",
cs.ConnectionString);

Console.WriteLine("#{0}", i);
Console.WriteLine(" Name: {0}", cs.Name);


Console.WriteLine(" Provider Name: {0}",
cs.ProviderName);

}

}


LOCAL MSDN:
ms-help://MS.VSCC.v80/MS.MSDN.v80/MS.NETDEVFX.v20.en/cpref4/html/T_System_Configuration_ConnectionStringSettings.htm
----------------------------------------
Knowledge is P...O...w...E...R!
My site