>>I have a DLL library that uses a configuration file to get a value which can be set at the client.
>>The configuration file contains:
>>

>> <appSettings>
>>    <add key="CertificateSerialNumber" value="SerialNumber"/>
>>  </appSettings>
>>

>>In the code of the library I try to get the serial number:
>>

>>SerialNumber = ConfigurationSettings.AppSettings["CertificateSerialNumber"];
>>

>>Which works fine in debug, but when executing the code at the client, the subsequent error occurs:
>>

>>Value cannot be Null
>>

>>So I assume it cannot find the parameter I am looking for. The config file is in the same folder as the dll, so what am I missing?
>
>The config file is based off of the entry executable, not the dll (see https://msdn.microsoft.com/en-us/library/ms229689.aspx). Do you have the config file in the same folder as the exe and named after the exe?

I couldn't believe it. The issue is that I call the DLL from a VFP executable so I assumed it would not make sense to call it that way. But indeed when naming the config the same as the VFP exe it works. Thanks for the help.