[VB.NET] Null Class

Utility 로 쓰면 어떨까 해서올립니다.
첫 소스는 codeproject 에서 가져왔는데요
조금 조금씩 수정했습니다.
코드보시면 이걸 왜 이렇게 했을까... 라는 생각을 갖게 하는 부분들이 있습니다. ㅋㅋ
필요하신 부분 있으시면 수정해서 사용하시면 좋을 듯합니다.
이런 코드도 있드라 정도로 생각해 두시면... ^^
이런식으로 자신만의 함수들을 따로 만들어 놓으시면
자신만의 프래임웍 유틸리티를 만들수 있겠죠? ^^


Imports System
Imports System.Reflection

Public Class Null

' define application encoded null values
Public Shared ReadOnly Property NullShort() As Short
  Get
    Return -1
  End Get
End Property
Public Shared ReadOnly Property NullInteger() As Integer
  Get
    Return -1
  End Get
End Property
Public Shared ReadOnly Property NullSingle() As Single
  Get
    Return Single.MinValue
  End Get
End Property
Public Shared ReadOnly Property NullDouble() As Double
  Get
    Return Double.MinValue
  End Get
End Property
Public Shared ReadOnly Property NullDecimal() As Decimal
  Get
    Return Decimal.MinValue
  End Get
End Property
Public Shared ReadOnly Property NullDate() As Date
  Get
    Return Date.MinValue
  End Get
End Property
Public Shared ReadOnly Property NullString() As String
  Get
    Return ""
  End Get
End Property
Public Shared ReadOnly Property NullBoolean() As Boolean
  Get
    Return False
  End Get
End Property
Public Shared ReadOnly Property NullGuid() As Guid
  Get
    Return Guid.Empty
  End Get
End Property

' sets a field to an application encoded null value ( used in BLL layer )
Public Shared Function SetNull(ByVal objValue As Object, ByVal objField As Object) As Object
If IsDBNull(objValue) Then
  If TypeOf objField Is Short Then
    Return NullShort
  ElseIf TypeOf objField Is Integer Then
    Return NullInteger
  ElseIf TypeOf objField Is Single Then
    Return NullSingle
  ElseIf TypeOf objField Is Double Then
    Return NullDouble
  ElseIf TypeOf objField Is Decimal Then
    Return NullDecimal
  ElseIf TypeOf objField Is Date Then
    Return NullDate
  ElseIf TypeOf objField Is String Then
    Return NullString
  ElseIf TypeOf objField Is Boolean Then
    Return NullBoolean
  ElseIf TypeOf objField Is Guid Then
    Return NullGuid
  Else ' complex object
    Return Nothing
  End If
Else ' return value
  Return objValue
End If
End Function

' sets a field to an application encoded null value ( used in BLL layer )
Public Shared Function SetNull(ByVal objPropertyInfo As PropertyInfo) As Object
  Select Case objPropertyInfo.PropertyType.ToString
    Case "System.Int16"
      Return NullShort
    Case "System.Int32", "System.Int64"
      Return NullInteger
    Case "System.Single"
      Return NullSingle
    Case "System.Double"
      Return NullDouble
    Case "System.Decimal"
      Return NullDecimal
    Case "System.DateTime"
      Return NullDate
    Case "System.String", "System.Char"
      Return NullString
    Case "System.Boolean"
      Return NullBoolean
    Case "System.Guid"
      Return NullGuid
    Case Else
      ' Enumerations default to the first entry
      Dim pType As Type = objPropertyInfo.PropertyType
      If pType.BaseType.Equals(GetType(System.Enum)) Then
        Dim objEnumValues As System.Array = System.Enum.GetValues(pType)
        Array.Sort(objEnumValues)
        Return System.Enum.ToObject(pType, objEnumValues.GetValue(0))
      Else ' complex object
        Return Nothing
      End If
    End Select
End Function

' convert an application encoded null value to a database null value ( used in DAL )
Public Shared Function GetNull(ByVal objField As Object, ByVal objDBNull As Object) As Object
  GetNull = objField
  If objField Is Nothing Then
    Return objDBNull
  ElseIf TypeOf objField Is Short Then
    If Convert.ToInt16(objField) = NullShort Then
      Return objDBNull
    End If
  ElseIf TypeOf objField Is Integer Then
    If Convert.ToInt32(objField) = NullInteger Then
      Return objDBNull
    End If
  ElseIf TypeOf objField Is Single Then
    If Convert.ToSingle(objField) = NullSingle Then
      Return objDBNull
    End If
  ElseIf TypeOf objField Is Double Then
    If Convert.ToDouble(objField) = NullDouble Then
      Return objDBNull
    End If
  ElseIf TypeOf objField Is Decimal Then
    If Convert.ToDecimal(objField) = NullDecimal Then
      Return objDBNull
    End If
  ElseIf TypeOf objField Is Date Then
' compare the Date part of the DateTime with the DatePart of the NullDate ( this avoids subtle time differences )
    If Convert.ToDateTime(objField).Date = NullDate.Date Then
      Return objDBNull
    End If
  ElseIf TypeOf objField Is String Then
    If objField Is Nothing Then
      Return objDBNull
    Else
      If objField.ToString = NullString Then
        Return objDBNull
      End If
    End If
  ElseIf TypeOf objField Is Boolean Then
    If Convert.ToBoolean(objField) = NullBoolean Then
      Return objDBNull
    End If
  ElseIf TypeOf objField Is Guid Then
    If CType(objField, System.Guid).Equals(NullGuid) Then
      Return objDBNull
    End If
  End If
End Function

' checks if a field contains an application encoded null value
Public Shared Function IsNull(ByVal objField As Object) As Boolean
  If Not objField Is Nothing Then
    If TypeOf objField Is Integer Then
      Return objField.Equals(NullInteger)
    ElseIf TypeOf objField Is Single Then
      Return objField.Equals(NullSingle)
    ElseIf TypeOf objField Is Double Then
      Return objField.Equals(NullDouble)
    ElseIf TypeOf objField Is Decimal Then
      Return objField.Equals(NullDecimal)
    ElseIf TypeOf objField Is Date Then
      Dim objDate As DateTime = CType(objField, DateTime)
      Return objDate.Date.Equals(NullDate.Date)
    ElseIf TypeOf objField Is String Then
      Return objField.Equals(NullString)
    ElseIf TypeOf objField Is Boolean Then
      Return objField.Equals(NullBoolean)
    ElseIf TypeOf objField Is Guid Then
      Return objField.Equals(NullGuid)
    Else ' complex object
      Return False
    End If
  Else
    Return True
  End If
End Function

End Class