datacolumn extendedproperties - are they always available?

[Bernie Yaeger]

I'm coming to a sad conclusion - it appears that datacolumn
extendedproperties only work if the datatable is part of a strongly typed
dataset.

Now this sounds odd, but I can't get this to work:

Dim davendor As New SqlDataAdapter("select vname, saddr, saddr2, scity,
sst, szip, baddr2 from vendor order by vname", oconn)
Dim dsvendor As New DataSet("vendor")

davendor.Fill(dsvendor, "vendor")

dsvendor.Tables(0).Columns("saddr2").ExtendedPrope rties.Add("nullValue",
String.Empty)

When the code gets around to this (in an 'i' loop),

glfs_addr2 = dsvendor.Tables(0).Rows(i)("saddr2")

it fails if the value of saddr2 is null, but ok if otherwise. The idea of
the extendedproperties that I had was to convert null to an empty string and
thus not fail here. I know I can solve this with a

If Not IsDBNull(dsvendor.Tables(0).Rows(i)("saddr2")) Then

but this is exactly what I was trying to avoid.

Thanks for any help.

Bernie Yaeger