Help With Multi Project Solution

Question

Hi Guys, first post here and hoping that someone can help me out.

I am currently developing a multi project solution in visual studio.  I have 2 main projects that both use the same business logic.  I want to be able to use one app.config throughout all my projects.  I have been scouring the net for the last day trying to find a solution that works for this, but i am yet to succeed.  An outline can be seen below of the code i am using from within my business logic:

public string returnConfigurationValue(string keyName)
{
string configurationValue = string.Empty;

ExeConfigurationFileMap fm = new ExeConfigurationFileMap();
 fm.ExeConfigFilename = @"CSITextServiceManagement.exe.config";
           
Configuration config = ConfigurationManager.OpenMappedExeConfiguration(fm, ConfigurationUserLevel.None);
AppSettingsSection appSettings =  AppSettingsSection)config.GetSection("appSettings");
foreach (string key in appSettings.Settings.AllKeys)
 {
appSettings.Settings[keyName].Value);
string value = appSettings.Settings[key].Value;
 configurationValue += string.Format("{0}{1}", key, value);
 }
 return configurationValue;
}

My app.config looks like this:

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
<appSettings>
<add key="serviceInterval" value="20000"/>
</appSettings>
</configuration>

When i return and output the contents of the function i get an empty string, which leads me to think that i am not referencing the app.config file properly. 

Could someone please advise on how i can resolve this issue as its driving me crazy.