请帮我在Vb.NET中创建Nullable字符串参数

Question

请告诉我如何在vb.net中实现string类型的Nullable Parameter

功能:

sub savedetail(byval name as string, byval age as integer)
if name isnot nothing then
some work
end if
end sub

我称之为事物

savedetail(nothing,34) //here is giving me format exception

exception:System.FormatException:输入字符串的格式不正确.

现在我正在放置exect功能..请告诉我我在哪里犯错误:

Function savedetails(ByVal db As DSLibrary.DataProviders.SqlProvider, ByVal name As String, ByVal cityId As Integer, ByVal addr1 As String, ByVal addr2 As String, ByVal phone As String, ByVal fax As String, ByVal zip As String, ByVal contactfname As String, ByVal contactlname As String, ByVal randomcode As String, ByVal reservationEmail As String, ByVal email As String, ByVal url As String, ByVal description As String, ByVal locationInfo As String, ByVal amenities As String, ByVal roomDetails As String, ByVal latitude As Double, ByVal longitude As Double, ByVal enabled As Integer, Optional ByVal hotelId As Integer = Nothing, Optional ByVal checkDuplicate As Boolean = True, Optional ByVal DSPartner As Integer = Nothing, Optional ByVal category As String = Nothing, Optional ByVal rating As Integer = Nothing) As Integer

电话:

savedetails(db, hotelname, 0, address, Nothing, Nothing, Nothing, postal, Nothing, Nothing, Nothing, Nothing, Nothing, Nothing, hotelinfo, Nothing, service, Nothing, Convert.ToDouble(lat), Convert.ToDouble(longi), 1, Convert.ToInt32(hotelid), False, dspartnerid)

Answer 1

Errrhm.默认情况下,字符串可以为空,因为它是引用类型.

在提供更多信息后进行编辑: 其中一个Convert.ToDouble()并且Convert.ToInt32()可能会抛出此异常.使用调试器并在调用上设置断点并检查这些转换的参数或将它们移出调用之外.