xenadmin/XenCenterLib/ToStringWrapper.cs

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

namespace XenCenterLib
{
    /// <summary>
    /// The delegate for the method that returns ToString() for the wrapped item.
    /// </summary>
    public delegate Object ToStringDelegate<T>(T t);

    /// <summary>
    /// A utility class for use with ListBox and other controls that take items of type Object and display
    /// them using their ToString() methods. By wrapping it in an instance of this class, a custom
    /// ToString() representation can be provided while allowing easy access to the original object.
    /// </summary>
    /// <typeparam name="T">The type of the wrapped object.</typeparam>
    public class ToStringWrapper<T> : IComparable<ToStringWrapper<T>>, IEquatable<ToStringWrapper<T>> where T : IEquatable<T>
	{
		#region For use with controls like DataGridViewComboBoxCell

		public const string ValueMember = "Self";

		public const string DisplayMember = "ToStringProperty";

		/// <summary>
		/// Gets the string returned by ToString()
		/// (Property wrapper for ToString(); this property's name can be used to set
		/// the DisplayMember property of controls like DataGridViewComboBoxCell)
		/// </summary>
		public string ToStringProperty { get { return ToString(); } }

		/// <summary>
		/// Returns this ToStringWrapper instance (can be used to set
		/// the ValueMember property of controls like DataGridViewComboBoxCell)
		/// </summary>
		public ToStringWrapper<T> Self { get { return this; } }

		#endregion

		/// <summary>
        /// The wrapped object.
        /// </summary>
        public readonly T item;

        /// <summary>
        /// The string returned by ToString() on this ToStringWrapper instance.
        /// </summary>
        private readonly string toString;
        /// <summary>
        /// The delegate executed to provide ToString() on this ToStringWrapper instance.
        /// </summary>
        private readonly ToStringDelegate<T> toStringDelegate;

        /// <summary>
        /// Takes and subsequently returns a fixed ToString() value.
        /// </summary>
        /// <param name="item">The item to wrap.</param>
        /// <param name="toString">The ToString() string that is returned by the new wrapper.</param>
        public ToStringWrapper(T item, string toString) {
            this.item = item;
            this.toString = toString;
        }

        /// <summary>
        /// Takes a ToStringDelegate, executed each time ToString() is called.
        /// </summary>
        /// <param name="item">The item to wrap.</param>
        /// <param name="toStringDelegate">A method that should return the desired ToString()
        /// value for the wrapped object. Calls to this ToStringWrapper's ToString() method
        /// evaluate the supplied delegate method and return its value.</param>
        public ToStringWrapper(T item, ToStringDelegate<T> toStringDelegate)
        {
            this.item = item;
            this.toStringDelegate = toStringDelegate;
        }

        public override string ToString()
        {
            System.Diagnostics.Trace.Assert(toString == null ^ toStringDelegate == null);
            if (toStringDelegate != null) {
                return toStringDelegate(item).ToString();
            } else {
                return toString;
            }
        }

        public bool Equals(ToStringWrapper<T> other)
        {
            return other != null && item.Equals(other.item);
        }

        public int CompareTo(ToStringWrapper<T> other)
        {
            if (item is IComparable<T>)
            {
                return (item as IComparable<T>).CompareTo(other.item);
            }
            else
            {
                return StringUtility.NaturalCompare(ToString(), other.ToString());
            }
        }
    }
}