smartdate.cs

C# 版本的一个三层商业架构

using System;
using CSLA.Resources;

namespace CSLA
{
  /// <summary>
  /// Provides a date data type that understands the concept
  /// of an empty date value.
  /// </summary>
  /// <remarks>
  /// See Chapter 5 for a full discussion of the need for this
  /// data type and the design choices behind it.
  /// </remarks>
  [Serializable()]
  sealed public class SmartDate : IComparable
  {
    DateTime _date;
    bool _emptyIsMin;

    #region Constructors

    /// <summary>
    /// Creates a new SmartDate object.
    /// </summary>
    public SmartDate()
    {
      _emptyIsMin = false;
      _date = DateTime.MaxValue;
    }

    /// <summary>
    /// Creates a new SmartDate object.
    /// </summary>
    /// <param name="emptyIsMin">
    /// Indicates whether an empty date is the min or max date value.</param>
    public SmartDate(bool emptyIsMin)
    {
      _emptyIsMin = emptyIsMin;
      if(_emptyIsMin)
        _date = DateTime.MinValue;
      else
        _date = DateTime.MaxValue;
    }

    /// <summary>
    /// Creates a new SmartDate object.
    /// </summary>
    /// <remarks>
    /// An empty date will be treated as the smallest
    /// possible date.
    /// </remarks>
    /// <param name="date">The initial value of the object.</param>
    public SmartDate(DateTime date)
    {
      _emptyIsMin = false;
      _date = date;
    }

    /// <summary>
    /// Creates a new SmartDate object.
    /// </summary>
    /// <remarks>
    /// An empty date will be treated as the smallest
    /// possible date.
    /// </remarks>
    /// <param name="date">The initial value of the object.</param>
    public SmartDate(string date)
    {
      _emptyIsMin = false;
      Text = date;
    }

    /// <summary>
    /// Creates a new SmartDate object.
    /// </summary>
    /// <param name="date">The initial value of the object.</param>
    /// <param name="emptyIsMin">
    /// Indicates whether an empty date is the min or max date value.</param>
    public SmartDate(DateTime date, bool emptyIsMin)
    {
      _emptyIsMin = emptyIsMin;
      _date = date;
    }

    /// <summary>
    /// Creates a new SmartDate object.
    /// </summary>
    /// <param name="date">The initial value of the object (as text).</param>
    /// <param name="emptyIsMin">
    /// Indicates whether an empty date is the min or max date value.</param>
    public SmartDate(string date, bool emptyIsMin)
    {
      _emptyIsMin = emptyIsMin;
      this.Text = date;
    }

    #endregion

    #region Text Support

    string _format = "{0:d}";

    /// <summary>
    /// Gets or sets the format string used to format a date
    /// value when it is returned as text.
    /// </summary>
    /// <remarks>
    /// The format string should follow the requirements for 
    /// standard .NET string formatting statements.
    /// </remarks>
    /// <value>A format string.</value>
    public string FormatString
    {
      get
      {
        return _format;
      }
      set
      {
        _format = value;
      }
    }

    /// <summary>
    /// Gets or sets the date value.
    /// </summary>
    /// <remarks>
    /// <para>
    /// This property can be used to set the date value by passing a
    /// text representation of the date. Any text date representation
    /// that can be parsed by the .NET runtime is valid.
    /// </para><para>
    /// When the date value is retrieved via this property, the text
    /// is formatted by using the format specified by the 
    /// <see cref="P:CSLA.SmartDate.FormatString" /> property. The 
    /// default is the "d", or short date, format.
    /// </para>
    /// </remarks>
    /// <returns></returns>
    public string Text
    {
      get
      {
        return DateToString(_date, _format, _emptyIsMin);
      }
      set
      {
        if(value == null)
          _date = StringToDate(string.Empty, _emptyIsMin);
        else
          _date = StringToDate(value, _emptyIsMin);
      }
    }

    /// <summary>
    /// Returns a text representation of the date value.
    /// </summary>
    public override string ToString()
    {
      return this.Text;
    }

    #endregion

    #region Date Support

    /// <summary>
    /// Gets or sets the date value.
    /// </summary>
    public DateTime Date
    {
      get
      {
        return _date;
      }
      set
      {
        _date = value;
      }
    }

    #endregion

    #region DBValue

    /// <summary>
    /// Gets a database-friendly version of the date value.
    /// </summary>
    /// <remarks>
    /// <para>
    /// If the SmartDate contains an empty date, this returns DBNull. Otherwise
    /// the actual date value is returned as type Date.
    /// </para><para>
    /// This property is very useful when setting parameter values for
    /// a Command object, since it automatically stores null values into
    /// the database for empty date values.
    /// </para><para>
    /// When you also use the SafeDataReader and its GetSmartDate method,
    /// you can easily read a null value from the database back into a
    /// SmartDate object so it remains considered as an empty date value.
    /// </para>
    /// </remarks>
    public object DBValue
    {
      get
      {
        if(this.IsEmpty)
          return DBNull.Value;
        else
          return _date;
      }
    }

    #endregion

    #region Empty Dates

    /// <summary>
    /// Indicates whether this object contains an empty date.
    /// </summary>
    /// <returns>True if the date is empty.</returns>
    public bool IsEmpty
    {
      get
      {
        if(_emptyIsMin)
          return _date.Equals(DateTime.MinValue);
        else
          return _date.Equals(DateTime.MaxValue);
      }
    }

    /// <summary>
    /// Indicates whether an empty date is the min or max possible date value.
    /// </summary>
    /// <remarks>
    /// Whether an empty date is considered to be the smallest or largest possible
    /// date is only important for comparison operations. This allows you to
    /// compare an empty date with a real date and get a meaningful result.
    /// </remarks>
    /// <returns>True if an empty date is the smallest 
    /// date, False if it is the largest.</returns>
    public bool EmptyIsMin
    {
      get
      {
        return _emptyIsMin;
      }
    }

    #endregion

    #region Conversion Functions

    /// <summary>
    /// Converts a text date representation into a Date value.
    /// </summary>
    /// <remarks>
    /// An empty string is assumed to represent an empty date. An empty date
    /// is returned as the MinValue.
    /// </remarks>
    /// <param name="date">The text representation of the date.</param>
    /// <returns>A Date value.</returns>
    static public DateTime StringToDate(string date)
    {
      return StringToDate(date, true);
    }

    /// <summary>
    /// Converts a text date representation into a Date value.
    /// </summary>
    /// <remarks>
    /// An empty string is assumed to represent an empty date. An empty date
    /// is returned as the MinValue or MaxValue of the Date datatype depending
    /// on the EmptyIsMin parameter.
    /// </remarks>
    /// <param name="date">The text representation of the date.</param>
    /// <param name="emptyIsMin">
    /// Indicates whether an empty date is the min or max date value.</param>
    /// <returns>A Date value.</returns>
    static public DateTime StringToDate(string date, bool emptyIsMin)
    {
      if(date.Length == 0)
      {
        if(emptyIsMin)
          return DateTime.MinValue;
        else
          return DateTime.MaxValue;
      }                                                                                          
      else
      {
        string ldate = date.ToLower();
        if(ldate==Strings.GetResourceString("SmartDateToday") ||
          ldate==Strings.GetResourceString("SmartDateT") ||
          ldate==".")
          return DateTime.Now;
        else
        {
          if(ldate==Strings.GetResourceString("SmartDateYesterday") ||
            ldate==Strings.GetResourceString("SmartDateY") ||
            ldate=="-")
          {
            return DateTime.Now.AddDays(-1);
          }
          else
          {
            if(ldate==Strings.GetResourceString("SmartDateTomorrow") ||
              ldate==Strings.GetResourceString("SmartDateTom") ||
              ldate=="+")
            {
              return DateTime.Now.AddDays(1);
            }
            else
            {
              return DateTime.Parse(date);
            }
          }
        }
      }
    }

    /// <summary>
    /// Converts a date value into a text representation.
    /// </summary>
    /// <remarks>
    /// The date value is considered empty assuming EmptyIsMin is true. 
    /// If the date is empty, this
    /// method returns an empty string. Otherwise it returns the date
    /// value formatted based on the FormatString parameter.
    /// </remarks>
    /// <param name="date">The date value to convert.</param>
    /// <param name="formatString">The format string used to format the date into text.</param>
    /// <returns>Text representation of the date value.</returns>
    static public string DateToString(DateTime date, string formatString)
    {
      return DateToString(date, formatString, true);
    }

    /// <summary>
    /// Converts a date value into a text representation.
    /// </summary>
    /// <remarks>
    /// Whether the date value is considered empty is determined by
    /// the EmptyIsMin parameter value. If the date is empty, this
    /// method returns an empty string. Otherwise it returns the date
    /// value formatted based on the FormatString parameter.
    /// </remarks>
    /// <param name="date">The date value to convert.</param>
    /// <param name="formatString">The format string used to format the date into text.</param>
    /// <param name="emptyIsMin">
    /// Indicates whether an empty date is the min or max date value.</param>
    /// <returns>Text representation of the date value.</returns>
    static public string DateToString(DateTime date, string formatString, 
                                      bool emptyIsMin)
    {
      if(emptyIsMin && (date == DateTime.MinValue))
        return string.Empty;
      else
        if(!emptyIsMin && (date == DateTime.MaxValue))
        return string.Empty;
      else
        return string.Format(formatString, date);
    }

    #endregion

    #region Operators

    static public bool operator > (SmartDate date1, SmartDate date2)
    {
      return date1.Date > date2.Date;
    }

    static public bool operator > (SmartDate date1, DateTime date2)
    {
      return date1.Date > date2;
    }

    static public bool operator < (SmartDate date1, SmartDate date2)
    {
      return date1.Date < date2.Date;
    }

    static public bool operator < (SmartDate date1, DateTime date2)
    {
      return date1.Date < date2;
    }

    static public bool operator == (SmartDate date1, SmartDate date2)
    {
      return Equals(date1, date2);
    }

    static public bool operator == (SmartDate date1, DateTime date2)
    {
      return Equals(date1, date2);
    }

    static public bool operator != (SmartDate date1, SmartDate date2)
    {
      return !Equals(date1, date2);
    }

    static public bool operator != (SmartDate date1, DateTime date2)
    {
      return !Equals(date1, date2);
    }

    static public SmartDate operator + (SmartDate d, TimeSpan t)
    {
      if (d.IsEmpty)
        return d;
      else
        return new SmartDate(d.Date + t, d.EmptyIsMin);
    }

    static public SmartDate operator - (SmartDate d, TimeSpan t)
    {
      if (d.IsEmpty)
        return d;
      else
        return new SmartDate(d.Date - t, d.EmptyIsMin);
    }

    public override bool Equals(object o)
    {
      if (o is SmartDate)
      {
        SmartDate tmp = o as SmartDate;
        if (this.IsEmpty && tmp.IsEmpty)
          return true;
        else
          return _date.Equals(((SmartDate)o).Date);
      }
      else if(o is DateTime)
        return _date.Equals((DateTime)o);
      else
        return false;
    }

    public override int GetHashCode()
    {
      return _date.GetHashCode ();
    }
    
    #endregion

    #region Manipulation Functions

    /// <summary>
    /// Compares one SmartDate to another.
    /// </summary>
    /// <remarks>
    /// This method works the same as the CompareTo method
    /// on the Date datetype, with the exception that it
    /// understands the concept of empty date values.
    /// </remarks>
    /// <param name="Value">The date to which we are being compared.</param>
    /// <returns>
    /// A value indicating if the comparison date is less than, 
    /// equal to or greater than this date.</returns>
    public int CompareTo(SmartDate date)
    {
      if(this.IsEmpty && date.IsEmpty)
        return 0;
      else
        return _date.CompareTo(date.Date);
    }

    int IComparable.CompareTo(object value)
    {
      if(value is SmartDate)
        return CompareTo((SmartDate)value);
      else
        throw new ArgumentException(Strings.GetResourceString("ValueNotSmartDateException"));
    }

    /// <summary>
    /// Adds a TimeSpan onto the object.
    /// </summary>
    public DateTime Add(TimeSpan span)
    {
      if (IsEmpty)
        return _date;
      else
        return  _date.Add(span);
    }

    /// <summary>
    /// Subtracts a TimeSpan from the object.
    /// </summary>
    public DateTime Subtract(TimeSpan span)
    {
      if (IsEmpty)
        return _date;
      else
        return  _date.Subtract(span);
    }

    /// <summary>
    /// Subtracts a DateTime from the object.
    /// </summary>
    public TimeSpan Subtract(DateTime date)
    {
      if (IsEmpty)
        return TimeSpan.Zero;
      else
        return _date.Subtract(date);
    }

    #endregion
  }
}