Building an Extensible Application with MEF, WPF, and MVVM

// 
// Copyright (c) 2004-2006 Jaroslaw Kowalski <jaak@jkowalski.net>
// 
// All rights reserved.
// 
// Redistribution and use in source and binary forms, with or without 
// modification, are permitted provided that the following conditions 
// are met:
// 
// * Redistributions of source code must retain the above copyright notice, 
//   this list of conditions and the following disclaimer. 
// 
// * Redistributions in binary form must reproduce the above copyright notice,
//   this list of conditions and the following disclaimer in the documentation
//   and/or other materials provided with the distribution. 
// 
// * Neither the name of Jaroslaw Kowalski nor the names of its 
//   contributors may be used to endorse or promote products derived from this
//   software without specific prior written permission. 
// 
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 
// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE 
// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 
// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 
// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 
// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 
// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF 
// THE POSSIBILITY OF SUCH DAMAGE.
// 

using System;
using System.Collections;

namespace NLog
{
    /// <summary>
    /// Global Diagnostics Context - a dictionary structure to hold per-application-instance values.
    /// </summary>
    public sealed class GDC
    {
        private static IDictionary _dict = new Hashtable();

        private GDC(){}

        /// <summary>
        /// Sets the Global Diagnostics Context item to the specified value.
        /// </summary>
        /// <param name="item">Item name.</param>
        /// <param name="value">Item value.</param>
        public static void Set(string item, string value)
        {
            _dict[item] = value;
        }

        /// <summary>
        /// Gets the Global Diagnostics Context named item.
        /// </summary>
        /// <param name="item">Item name.</param>
        /// <returns>The item value of String.Empty if the value is not present.</returns>
        public static string Get(string item)
        {
            string s = (string)_dict[item];
            if (s == null)
                return String.Empty;
            else
                return s;
        }

        /// <summary>
        /// Checks whether the specified item exists in the Global Diagnostics Context.
        /// </summary>
        /// <param name="item">Item name.</param>
        /// <returns>A boolean indicating whether the specified item exists in current thread GDC.</returns>
        public static bool Contains(string item)
        {
            return _dict.Contains(item);
        }

        /// <summary>
        /// Removes the specified item from the Global Diagnostics Context.
        /// </summary>
        /// <param name="item">Item name.</param>
        public static void Remove(string item)
        {
            _dict.Remove(item);
        }

        /// <summary>
        /// Clears the content of the GDC.
        /// </summary>
        public static void Clear()
        {
            _dict.Clear();
        }
    }
}