A WPF Template solution using MVVM and Castle Windsor

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Interfaces
{
    public interface IConfig
    {
        /// <summary>
        /// Gets or sets the installation path.
        /// </summary>
        /// <value>
        /// The installation path.
        /// </value>
        string InstallationPath { get; set; }

        /// <summary>
        /// Gets or sets a value indicating whether [use local configuration].
        /// </summary>
        /// <value>
        /// <c>true</c> if [use local configuration]; otherwise, <c>false</c>.
        /// </value>
        bool UseLocalConfig { get; set; }

        /// <summary>
        /// Gets the global configuration file.
        /// </summary>
        /// <value>
        /// The global configuration file.
        /// </value>
        string GlobalConfigFile { get; }

        /// <summary>
        /// Creates the or update setting.
        /// </summary>
        /// <param name="fileName">Name of the file.</param>
        /// <param name="key">The key.</param>
        /// <param name="value">The value.</param>
        void CreateOrUpdateSetting(string fileName, string key, string value);

        /// <summary>
        /// Gets the setting.
        /// </summary>
        /// <param name="key">The key.</param>
        /// <returns></returns>
        string GetSetting(string key);

        /// <summary>
        /// Gets the setting.
        /// </summary>
        /// <param name="fileName">Name of the file.</param>
        /// <param name="key">The key.</param>
        /// <returns></returns>
        string GetSetting(string fileName, string key);

        /// <summary>
        /// Updates the configuration parameter.
        /// </summary>
        /// <param name="fileName">Name of the file.</param>
        /// <param name="parameter">The parameter.</param>
        /// <param name="value">The value.</param>
        void UpdateConfigParameter(string fileName, string parameter, string value);

        /// <summary>
        /// Loads the file.
        /// </summary>
        /// <param name="fileName">Name of the file.</param>
        void LoadFile(string fileName);

        /// <summary>
        /// Reads the global configuration file.
        /// </summary>
        void ReadGlobalConfigFile();

        /// <summary>
        /// Reads the specified file name.
        /// </summary>
        /// <param name="fileName">Name of the file.</param>
        void Read(string fileName);
    }
}