passing Null dates as parameters to functions

Question

Hi

What's the best way of passing in Null / empty date fields as parameters to functions ?

What's the best way of passing in a date into a VB function as a null/empty value - at the moment I am checking to see if it = #12:00:00 AM# , but this seems somewhat haphazard !

thanks
Bruce

 

Answer 1

Test if date variable is nothing:

    Dim testDate As Date = Nothing

 

    MsgBox(DateIsNull(testDate))

 

    testDate = Date.Now

 

    MsgBox(DateIsNull(testDate))

 

 

    Private Function DateIsNull(ByVal testDate As Date) As Boolean

        If testDate.Equals(Nothing) Then

            Return True

        End If

 

        Return False

    End Function

 

Answer 2

If you are using VB 2005, you can use the Nullable(Of Date) as your parameter. Of course, that would mean you would need to either use a Nullable(Of Date) property/field that you were passing or create a new Nullable(Of Date) that you pass in to the method. Once you have a Nullable(Of Date), you can see if it is empty by checking the .HasValue property. Here's a small snippet:

Dim x As New Nullable(Of Date)

x = #1/1/2006#

Debug.WriteLine(x.HasValue)

Jim Wooley
http://devauthority.com/blogs/jwooley/default.aspx