vb.net - 检查自定义代码函数中的 NULL 日期

Question

我正在尝试为 SSRS 报告实现一个函数，该函数将根据三个日期的值返回颜色值:

Function SetBoxColor(dateOne As Date, dateTwo As Date, dateThree As Date) As String
' Determine colors for text box
  If (dateOne Is Nothing) Then
    SetBoxColor = "Blue"
  Else
    If (dateThree Is Nothing) Then
      If dateOne >= Date.Now Then
        If DateDiff("d",dateOne,Date.Now) < 90
          SetBoxColor = "Yellow"
        Else
          SetBoxColor = "White"
        End If
      Else
        SetBoxColor = "Orange"
      End If
    Else
      If dateThree <= dateOne Or (Month(dateThree) = Month(dateOne) And Year(dateThree) = Year(dateOne)) Then
        SetBoxColor = "Green"
      Else
        SetBoxColor = "Red"
      End If
    End If
  End If
  Return SetBoxColor
End Function

传递给此函数的参数是我的数据集中的可为空日期(SQL Server 日期类型)，我从 TextBox 的 BackgroundColor 属性调用该函数，如下所示:

=Code.SetBoxColor(Fields!dateOne.Value, Fields!dateTwo.Value, Fields!dateThree.Value)

按原样运行该函数会返回错误:

'Is' requires operands that have reference types, but this operand has the value type 'Date'.

如有任何帮助，我们将不胜感激。

Answer 1

您尝试过dateOne = Nothing吗？