dynamically named controls

  • Thread starter Thread starter Pete Morris
  • Start date Start date
P

Pete Morris

question about VB 2005 express .

is it possible to refer to controls dynamically?

I mean instead of referring to [ textbox1.text] can I have a

mystring = "textbox1"

then refer to the control named in mystring?

Is that possible? What's the syntax for it?

specifically, I have textboxes named book_1 to book_9
I want to have a loop where I refer to properties of the
textbox named "book_" + str(loop_count)

how do I do that?
 
If you have a control (or any object reference) stored in a variable, then
you surely can set another variable to it.

Dim A As New Object
Dim B As Object
B = A

But to refer to an object variable using string parsing, really can't be
done unless you get into using the Reflection API.

So, your loop scenario below is not really possible in .NET. There are
other ways to iterate through controls. The simplest would be to add the
controls to a collection object and then iterate through the collection,
rather than by name, you'd access the control by its index in the
collection.

For Each item As Textbox In myTextboxesCollection
item.Text = "blah..."
Next


-Scott
 
question about VB 2005 express .

is it possible to refer to controls dynamically?

I mean instead of referring to [ textbox1.text] can I have a

mystring = "textbox1"

then refer to the control named in mystring?

Is that possible? What's the syntax for it?
Click to expand...

That depends. As Scott says, if you are specifically looking for the
variable name, that would require using reflection.

However, my guess is that you probably don't really want the variable
name. You want the control instance itself. And that you can in fact
get by name.
specifically, I have textboxes named book_1 to book_9
I want to have a loop where I refer to properties of the
textbox named "book_" + str(loop_count)
Click to expand...

Assuming you've left the Name property as the default, it should be the
same name as the instance variable referencing the control. So,
assuming "book_1" to "book_9" are valid Name values, you can do
something like this:

Control ctlParent = ...;

for (int itbx = 1; itbx <= 9; itbx++)
{
TextBox tbx;
Control[] rgctl = ctlParent.Find("book_" + itbx.ToString(), true);

tbx = (TextBox)rgctl[0];

// do something with the textbox instance referred to by tbx
}

The above code assumes that you will always find at least one with the
given name. It's also not terribly efficient, being essentially
O(N^2). But for a small number of controls, it should be fine.

That said, if you expect this to be a performance issue, there are
definitely better ways to accomplish the basic behavior you want
without doing exactly the above. It all just depends on the exact
context of what you're doing.

A couple of alternatives:

* Pre-process the search, and save a collection (I'd use
List<TextBox>, but anything would be fine) that you can enumerate at
will later

* Enumerate all the children once, checking each name for matching
against the general pattern, and processing any control that looks like
"book_#" where # is a digit from 1 to 9. You can use Regex or String
class methods to compare the string, and parse the digit to extract the
index so that you can process that particular control according to its
index.

There are lots of other possibilities. It's impossible to say what
would work best for you without more information, but some variation on
the above methods is likely to be suitable.

Pete
 
For i = 1 to 9
CType(Me.Controls("Book_" & i.ToString),TextBox).WhatEverPropertyYouWant
Next

Hope this helps,
Barry
 
Back
Top