Constructors Continued from Part 1...

We will need a series of constructors which will be used when we create Widening Operators, later. The first we aill use will accept a parameter value for ticks as an Int64. We will set the date using our InternalDate property as this will handle setting the inherited _isNull field for us.

    ''' <summary>
    ''' Initializes a new instance of the <see cref="DateTimeNull" /> class to a specified number of ticks.
    ''' </summary>
    ''' <param name="ticks">The ticks.</param>
    Public Sub New(ByVal ticks As Long)
        MyBase.New()
        Me.InternalDate = New System.DateTime(ticks)
    End Sub

The next constructor will take a System.DateTime parameter to construct our object.

    ''' <summary>
    ''' Initializes a new instance of the <see cref="DateTimeNull" /> class using the specified System.DateTime value.
    ''' </summary>
    ''' <param name="value">The value.</param>
    Public Sub New(ByVal value As System.DateTime)
        Me.New(value.Ticks)
    End Sub

The following constructor will take a System.Data.SqlTypes.SqlDateTime parameter to construct our object.

    ''' <summary>
    ''' Initializes a new instance of the <see cref="DateTimeNull" /> class using the specified System.Data.SqlTypes.SqlDateTime value.
    ''' </summary>
    ''' <param name="value">The value.</param>
    Public Sub New(ByVal value As System.Data.SqlTypes.SqlDateTime)
        MyBase.New()
        Dim dt As System.DateTime
        dt = Convert.ToDateTime(value)
        Me.InternalDate = dt
    End Sub

The last constructor will take a System.DBNull to construct or object.

    ''' <summary>
    ''' Initializes a new instance of the <see cref="DateTimeNull" /> class using a system.DBNull object.
    ''' </summary>
    ''' <param name="value">The value.</param>
    Public Sub New(ByVal value As System.DBNull)
        Me.New(System.DateTime.MinValue)
        If Not Me.IsNull Then
            Me.SetIsNull(True)
        End If
    End Sub

With our constructors done we will take a quick look at some of the properties which may be useful. Each property will reflect one of the properties that the .Net System.Datetime object has. Reflector is a useful tool for investigating these. Each property will expose the underlying InternalDate's properties, but first it must check if our object is in the NULL state. I have included just a few properties so you can see the pattern used.

    ''' <summary>
    ''' Gets the date component of this instance.
    ''' </summary>
    ''' <value>A new DateTime with the same date as this instance, and the time value set to 12:00:00 midnight (00:00:00).</value>
    ''' <exception cref="ArgumentNullException">Thrown</exception>
    Public ReadOnly Property [Date]() As DateTimeNull
        Get
            If Me.HasValue Then
                Return New DateTimeNull(Me.InternalDate.Date)
            Else
                Throw New ArgumentNullException("Date cannot be returned for a null DateTimeNull")
            End If
        End Get
    End Property

    ''' <summary>
    ''' Gets the day of the month represented by this instance.
    ''' </summary>
    ''' <remarks>The day component, expressed as a value between 1 and 31.</remarks>
    Public ReadOnly Property Day() As System.Int32
        Get
            If Me.HasValue Then
                Return Me.InternalDate.Day
            Else
                Throw New NullReferenceException("Day cannot be expressed for a null DateTimeNull object. ")
            End If
        End Get
    End Property

    ''' <summary>
    ''' Gets the hour component of the date represented by this instance.
    ''' </summary>
    ''' <returns>The hour component, expressed as a value between 0 and 23, inclusive.</returns>
    Public ReadOnly Property Hour() As System.Int32
        Get
            If Me.HasValue Then
                Return Me.InternalDate.Hour
            Else
                Throw New NullReferenceException("Hour cannot be expressed for a null DateTimeNull object. ")
            End If
        End Get
    End Property

    ''' <summary>
    ''' Gets a System.DateTime object that is set to the current date and time on this computer, expressed as the local time.
    ''' </summary>
    ''' <returns>A DateTime whose value is the current local date and time.</returns>
    Public Shared ReadOnly Property Now() As DateTime
        Get
            Return DateTime.UtcNow.ToLocalTime
        End Get
    End Property

    ''' <summary>
    ''' Gets the current date.
    ''' </summary>
    '''<returns>A DateTime set to today's date, with the time component set to 00:00:00.</returns>
    Public Shared ReadOnly Property Today() As DateTime
        Get
            Return DateTime.Now.Date
        End Get
    End Property

Over time I will add more properties to my DateTimeNull object, as they are required. Next however, it is time to look at Operators. This will be in Part 3.