Cannot set Nullable DateTime property

Question

I have the following code which I am trying to get data from the database for a Nullable DateTime Field in SQL Server -

 If dr("SendDate") Is DBNull.Value Then
      ctrl_prov_dtl.SelectedDateSendDate = DirectCast(Nothing, System.Nullable(Of DateTime))
 Else
      ctrl_prov_dtl.SelectedDateSendDate = dr("SendDate")
 End If

This is calling the following Public Property

Public Property SelectedDateSendDate() As Nullable(Of DateTime)
    Get
        Dim myDateTime As DateTime

        If (DateTime.TryParse(calSendDate.Text, myDateTime)) Then
            Return calSendDate.Text
        Else
            Return "01/01/1900"
        End If
    End Get
    Set(value As Nullable(Of DateTime))
       calSendDate.Text = value
    End Set
End Property

I keep getting the following error Nullable object must have a value.

I am really confused because I am setting the value to a Nullable(Of DateTime)

Answer 1

It's likely because you are trying to set the text value of calSendDate to value regardless if it's null or not.

Instead, change your property setter to this:

Set(value As Nullable(Of DateTime))
   If value.HasValue Then
       calSendDate.Text = value
   Else
       calSendDate.Text = Nothing
   End If
End Set

Additional advice:

If your project is .NET 3.5 or above and references System.Data.DataSetExtensions.dll, change your first block of code to this instead:

ctrl_prov_dtl.SelectedDateSendDate = dr.Field(Of DateTime?)("SendDate")

Also, your property getter never returns the parsed myDateTime value. And returning 1/1/1900 as the fallback value on a nullable type feels very wrong to me.