Specified cast is not valid

[Web Team @ Borough of Poole]

Can anyone help with this error...

"Specified cast is not valid."


Which I am getting with this code...
(Line 223)

Line 221: 'Handles data paging
Line 222: Public Sub PagerButtonClick(ByVal sender As System.Object,
ByVal e As System.EventArgs) Handles btnPager.Click
Line 223: Dim arg As String = CType(sender,
Button).CommandArgument
Line 224: Select Case arg
Line 225: Case "next" 'The next Button was


I casted sender to button in order to fix a 'late binding' error I had
after switching option strict on.

 

[Patrice]

The CommandArgument is an object if I remember. You'll have to cast it to a
string...

You can use DirectCast for the button and CStr for the CommandArgument...

 

[Web Team @ Borough of Poole]

Thanks Patrice

I tried this:
Dim arg As String = DirectCast(sender, Button).CommandArgument

But it still comes back with the same error.

 

[Patrice]

I meant try :
Dim arg As String=CStr(DirectCast(Sender,Button).CommandArgument)

(IMO the problem is that CommandArgument is an object not a string)

Does it work ?

If not try just :
Response.Write(Sender.GetType.ToString)
Response.Write(Sender.CommandArgument.GetType.ToString)
and adds temporarily Option Strict Off at the top of your source file...

This way it writes down the types and you should then know how to cast them
(think to remove Option Strict Off)...

CType works as well but if I remember DirectCast conduct the fact that
sender *is* a button while with CType you could have a button or whatever
inherits from a button (will fails otherwise, perhaps a bit quicker but
unlikely noticeable). I shouldn't have mentionned this, not relevant here...

Hope I'm a bit clearer now...

 

[Web Team @ Borough of Poole]

Thank you Patrice,

Using your tip to response.write the type, I discovered it was actually
a linkbutton, not a button - Hence the invalid cast.

Much appreciated.

Simon.

 

[Patrice]

Ah great !!! I'm really delighted to see that sometimes it's better to
suggest how to diagnose by yourself a problem rather than trying to solve it
at your place ;-)

Patrice