Checking NULL value in VB.NET

从数据库中获取datatable型的数据后在页面上显示时，报出如下错误：

Conversion from type 'DBNull' to type 'Date' is not valid.

原因就是对于DBNull的数据要通过程序处理，处理方法如下：

Public Enum enumObjectType

StrType = 0

IntType = 1

DblType = 2

DateType = 3

End Enum

''' <summary>

''' 判断是否为数据库NULL类型的数据，是，则转成数据类型

''' </summary>

''' <param name="obj"></param>

''' <param name="ObjectType"></param>

''' <returns></returns>

''' <remarks></remarks>

Public Shared Function CheckDBNull(ByVal obj As Object, _

Optional ByVal ObjectType As enumObjectType = enumObjectType.StrType) As Object

Dim objReturn As Object

objReturn = obj

If IsDBNull(obj) = True Then

Select Case ObjectType

Case enumObjectType.StrType

objReturn = ""

Case enumObjectType.IntType

objReturn = 0

Case enumObjectType.DblType

objReturn = 0.0

Case enumObjectType.DateType

objReturn = New Date

End Select

End If

Return objReturn

End Function