app.config (SIMPLE)

No, each key must be unique.

On the other hand, if you use XML, and serialize the data into a class, you can easily create an array of values.

Here's a sample from code that I use all the time:

[App.Config]



</xml version="1.0" encoding="utf-8" ?>
<configuration>

  <configSections>
    <section name="Section1"
             type="ConfigSectionHandler.ConfigSectionHandler, ConfigSectionHandler" />
    <section name="Section2"
             type="ConfigSectionHandler.ConfigSectionHandler, ConfigSectionHandler" />
  </configSections>

  <Section1 type="Namespace.Class, Namespace">
     <FormName>MyForm1</FormName>
     <FormName>MyForm2</FormName>
     <FormName>MyForm3</FormName>
     <FormName>MyForm4</FormName>
     <FormName>MyForm5</FormName>
  </Section1>
</configuration>

[Add this class to your application]


using System;
using System.Xml;
using System.Xml.XPath;
using System.Xml.Serialization;
using System.Configuration;

namespace ConfigSectionHandler
{
    /// <summary>
    /// This class contains only one method, Create().
    /// This is designed to handle custom sections in an Applications Configuration file.
    /// By Implementing <see cref="IConfigurationSectionHandler"/>, we can implement the
    /// Create method, which will provide the XmlNode from the configuration file. This is
    /// Deserialized into an object and passed back to the Caller.
    /// </summary>
    /// <example>
    /// Here is a configuration file entry in the <c>configSections</c> sectikon of the <c>App.Config</c>
    /// file.
    ///<code>      ///
    ///&lt;section name="ServerConfig" type="ConfigSectionHandler.ConfigSectionHandler, ConfigSectionHandler" /&gt;
    ///</code>
    ///This tells the CLR that there is a section further in, with a node name of <c>ServerConfig</c>. When this section
    ///is to be parsed, an object of type <c>ConfigSectionHandler.ConfigSectionHandler</c> which resides in the
    ///assembly <c>ConfigSectionHandler</c> will be instantiated. The CLR automatically calls a method in that object
    ///called <c>Create</c>
    ///</example>
    public class ConfigSectionHandler : IConfigurationSectionHandler
    {
        public ConfigSectionHandler()
            : base()
        {
        }

        #region IConfigurationSectionHandler Members

        /// <summary>
        /// A method which is called by the CLR when parsing the App.Config file. If custom sections
        /// are found, then an entry in the configuration file will tell the runtime to call this method,
        /// passing in the XmlNode required.
        /// </summary>
        /// <param name="parent">The configuration settings in a corresponding parent configuration section. Passed in via the CLR</param>
        /// <param name="configContext">An <see cref="HttpConfigurationContext"/> when Create is called from the ASP.NET configuration system. Otherwise,
        /// this parameter is reserved and is a null reference (Nothing in Visual Basic). Passed in via the CLR</param>
        /// <param name="section">The <see cref="XmlNode"/> that contains the configuration information from the configuration file.
        /// Provides direct access to the XML contents of the configuration section.       Passed in via the CLR.</param>
        /// <returns>The Deserialized object as an object</returns>
        /// <exception cref="System.Configuration.ConfigurationException">The Configuration file is not well formed,
        /// or the Custom section is not configured correctly, or the type of configuration handler was not specified correctly
        /// or the type of object was not specified correctly.
        /// or the copn</exception>
        public object Create(object parent, object configContext, System.Xml.XmlNode section)
        {
            try
            {
                XPathNavigator xNav = section.CreateNavigator();
                string typeOfObject = (string)xNav.Evaluate("string(@type)");
                Type t = Type.GetType(typeOfObject);
                XmlSerializer ser = new XmlSerializer(t);
                XmlNodeReader xNodeReader = new XmlNodeReader(section);
                return ser.Deserialize(xNodeReader);
            }
            catch (Exception e)
            {
                Console.WriteLine(e.Message);
                if (e.InnerException.Message.Length > 0)
                    Console.WriteLine(e.InnerException.Message);
                return null;
            }
           
        }
        #endregion
    }
}

[Create a class that you serialize your app.config data to]

using System;
using System.Collections.Generic;
using System.Text;
using System.Xml;
using System.Xml.Serialization;

namespace Application1
{
    [XmlRoot("Section1")]
    public class FirstSection
    {
        [XmlElement("FormName")]
        public string[] _formName;    }
}