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Hide image control if no imageurl is returned from DB

Posted on 2007-11-25
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Last Modified: 2013-11-06
Hello, I have used the following code in the past to hide an image control if the ImageURL is null but for some reason it is not working in this situation. Why can't this work?

I'm getting the following error on this line:
   If CType(Picture, String) Is DBNull.Value Then

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


Markup:
<asp:Image ID="image" runat="server" ImageUrl= '<%# "~/EventGraphics/" & Eval("ImageURL") %>'
                    Visible='<%# CheckImage(Container.DataItem("ImageURL")) %>'/>


Function:

 Public Function CheckImage(ByVal Picture As Object) As Boolean

        If CType(Picture, String) Is DBNull.Value Then
            Return False
        Else
            Return True
        End If
    End Function
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Question by:gogetsome
3 Comments
 
LVL 14

Accepted Solution

by:
steveberzins earned 1500 total points
ID: 20348213
I think you want to use this:

 If Picture = DBNull.Value Then
        Return False
        Else
            Return True
        End If

not 100% sure, but think the problem is CType is going to make a string, and the compiler knows that there is not a string equivalent of DBNull.Value, so this will never be true. I've not done a lot of vb.net, but usually the Is keyword used for comparing types, not values, and usually used to do something like if x Is Nothing, or if x is String, not if x is String.Empty. maybe someone can explain this better, but I don't think 'Is' is ever really appropriate for value comparisons. (unless you happen to be a popular past president, then is has a whole different meaning :)
0
 
LVL 39

Expert Comment

by:Pratima Pharande
ID: 20348494
<asp:Image ID="image" runat="server" ImageUrl= '<%# "~/EventGraphics/" & Eval("ImageURL") %>'
                    Visible='<%# CheckImage(Eval("ImageURL")) %>'/>



Public Function CheckImage(ByVal Picture As String) As String

        If  Picture <> "" Then
               
            Return  "True"
else
 Return  "False"

                   
        End If
    End Function
0
 

Author Comment

by:gogetsome
ID: 20350083
LOL, I must be a past president..

This did not work:
 If Picture = DBNull.Value Then
        Return False
        Else
            Return True
        End If

But this did:
 If Picture Is DBNull.Value Then
            Return False
        Else
            Return True
        End If

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