[02/03][Resolved] declaration issue--4th post onwards

[indiewolf]

i am trying to shorten my code, so instead of having errorprovider for each textbox i want to programatically reduce using something like the following.
although i dont get any errors, it doesnt do the work either.please help
cheers
For Each txerr As Control In firstMdiChild.Controls
If TypeOf txerr Is TextBox Then
'here i want to declare many textboxes , two in this example.
'if i declare one it works, but as soon as i declare more it doesn't work.
Dim errpro() As String = {"TextBox6", "TextBox7"}
'here i am comparing the name of the textbox with errpro
If txerr.Name Is errpro Then
ErrorProvider1.SetError(txerr, "Cannot leave blank")
Else
ErrorProvider1.SetError(txerr, "")
End If
End If
Next

[jmcilhinney]

If txerr.Name Is errpro Then

txterr.Name is a String and errpro is an array of String. That's like saying "if this egg is this egg carton". That can never be true.

Even if they were both Strings you'd should still be using the '=' operator, not the 'Is' operator. You want to know if the strings contain the same text, not whether they are the same object.

What you actually want to do is test whether the string is an element of the array, for which you would use the Array.IndexOf method. If IndexOf returns -1 then the value is not in the array, otherwise its index is returned.

[indiewolf]

brilliant reply.
that was exactly i was looking for. array.index of ruleth!!

cheers buddy

[indiewolf]

one more thing.

i have come to this problem many a times.

suppose i have a code like the following

For Each txerr As Control In firstMdiChild.Controls
            If TypeOf txerr Is TextBox Then
                Dim errpro() As String = {"TextBox6", ", "TextBox56", _
 "TextBox57", "TextBox58", "TextBox59","ComboBox1", _
               "ComboBox2", "ComboBox5", "ComboBox6", _
               "ComboBox7", ", "ComboBox11"}

now since i have declared it as form.controls , it restricts me to only textboxes on the form.
textboxes inside groupboxes, comboboxes etc aren't handled.
so why can't i write something like

for each txerr as control in firstmdichild.controls,firstmdichild.groupbox1.controls
if type of txerr is textbox  and combobox then

please suggest some solution
cheers

[jmcilhinney]

Because that's not legal syntax. If you understand how the language works then you understand why. The For Each loop is a construct that wraps the use of an IEnumerator object. When you iterate over a collection using a For Each loop you are implicitly calling the GetEnumerator method of that collection and and repeatedly calling its MoveNext method. One For Each loop cannot do that for two collections. If you want to iterate over two collections then you use two For Each loops. That said, if you want to visit nested controls then you should either use recursion or the GetNextControl method, whose use I've demonstrated in the VB.NET CodeBank forum.

Apart from that, this line makes no sense either:

if type of txerr is textbox  and combobox then

It's obvious what you're trying to do but even if the language did work that way that would still be wrong. How can a control be a TextBox AND a ComboBox? You should at least ne using OR rather than AND, but you're simply choosing to ignore how logical operators work. They require a Boolean expression on both sides. (TypeOf txerr Is TextBox) is a Boolean expression but (ComboBox) isn't. What you want to do is quite simple but you have to do it within the constraints of acceptable VB syntax:

If TypeOf txerr Is TextBox OrElse TypeOf txerr Is ComboBox Then