How to get values from app settings section

Suppose we have

<appSettings>      
 <add key="RuleMaster" value="DataSource\RuleMaster.xml"/>    
</appSettings>

To get the value from "RuleMaster", let us write the below code

 public string GetSettingValue(string configKey)
 {
   try
   {
       return System.Configuration.ConfigurationManager.AppSettings[configKey].ToString();
   }
   catch (Exception ex)
   {
       return string.Empty;
    }
 }

Use it : GetSettingValue("RuleMaster");