Getting values from dynamically created textboxes

Hello,

I'm creating a textboxes boxes dynamically when the user presses a button. I'm then adding the textbox to a placeholder. After the user enters data, I want to get the value that they entered, but I'm having trouble. The second method ReadTextBoxes is also being triggered by a button. The problem is that if they user chooses to had 3 new textboxes in the first method, the placeholder will contain 3 controls, but then when I click the button to read the textboxes, the placeholder is showing zero controls. What am I doing wrong? Thanks
// This creates the textboxes based on number requested by user
protected void AddEducation_Click(object sender, EventArgs e)
{
if (ExtraTextBox.Text == String.Empty)
{
ExtraTextBox.Text = "0";
}

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