problem with using split and looping it to check a value in C#

I have set the following key values in a config file:

<add key="noInviteReminder" value="SPN200|MC679|VN230"/>

So now I have to do a loop to figure out whether these above values exist and if they exist, the set a flag to true.  Then based on that flag, I have to do some thing.  But my problem is how do I check the flag for all the above?  When I hard code as follows it works.

string defaultN ...