assuming you only have 10 textboxes on one form you can either
Dim Str as string = ""
for each ctrl as control on form1.controls
if typeof ctrl is textbox then
if str.length = "" then
str += ctrl.text
else
str += "," ctrl.text
end
end if
next
or
dim str as string = ""
str = textbox1.text & "," & textbox2.text & "," textbox3.text