Navision SSRS the IIF executes Else when it is TRUE?

Question

(rewrote of the problem)

I have trouble to display an image in the footer. The issue is, I try to convert an image from the DB to a Base64 String. In case of get an image is is working, but if in the db is a null value the Textfield displays #ERROR.

IIF(IsNothing(Fields!Company_Picture.Value), "", Convert.ToBase64String(Fields!Company_Picture.Value))

I expected the else tree isn't executed in the case of IsNothing = True. But in the Report the TextField displays always #ERROR, if there is no image.

Solution is:

Public Function Base64String(ByVal img() as byte)
  if not isNothing(img) then
    Return Convert.ToBase64String(img)
  end if
  Return ""
end function

Thanks to all :-)

--- first try to cover my problem but it don't hit the main problem exact enougt ---

I have in the Report Code part Shared Data1 as Object

Public Function GetData(Num as Integer, Group as integer) as Object
if Group = 1 then
   Return Cstr(Choose(Num, Split(Cstr(Data1),Chr(177))))
End If
End 

and the same to set the data.

In the DB I have a image stored as blob. The direct displaying in the Report is working. Now I have to show the image in footer of the report. I have made a Table and inside of one cell I use the hidden Expression to insert the Image to the object.

Here is now the issue. I try to make it with

Code.SetData(IIF(IsNothing(First(Fields!CompanyPicture.Value, "DataSet_Result")) = TRUE, "", Convert.ToBase64String(Fields!CompanyPicture.Value) + Chr(177), 1)

The report crashes now on this expression, because the Hidden Expression can't be NULL. I do not understand, why from the IIF the else tree is executed. The IsNothing works correct and gives me True.

Any ideas what I can do, if the Image is Null?

Answer 1

As well as the comments in @Schlaagi's answer. IIF always evaluates both the true and false outcome so it will fail unless you accommodate this properly.

I don't know what the SetData function does and it's been a while since I've used Convert.ToBase64String but have a look at this and see if it makes sense.

=Code.SetData(
    Convert.ToBase64String(
                            IIF(IsNothing(Fields!CompanyPicture.Value, "DataSet_Result"),
                                "",
                                Fields!CompanyPicture.Value + Chr(177))
                            )
                            , 1
            )