foreach loop over TextBoxes in GroupBox iterates in reverse order?

Question

I created four TextBox es (in this order: textBox1 , textBox2 ,...) and put them one below the other inside a GroupBox . Then I added the Click event:

private void button1_Click(object sender, EventArgs e)
{
    foreach (TextBox tb in groupBox1.Controls.OfType<TextBox>())
    {
        if (string.IsNullOrWhiteSpace(tb.Text))
        {
            Console.WriteLine(tb.Name);
        }
    }
}

When I run the program and click the Button (when all the TextBox es are empty), this is the output I get:

textBox4

textBox3

textBox2

textBox1

Apparently the foreach loop iterated over the GroupBox controls in reverse order. I expected it to do it from textBox1 to textBox4 because this was the order they were created and put in the groupbox.

Why did the foreach loop in reverse? Just curious...

Answer 1

The controls are placed in order of the Z-order of the controls in the same parent container (top-most to bottom-most). How do you want to order them?

Answer 2

Try this

foreach (TextBox txt in Controls.OfType<GroupBox>().SelectMany(g=>g.Controls.OfType<TextBox>()).ToList().Reverse<TextBox>())
        {
            //Write your logic here
        }