ASP.NET TextBox ignores update panel

I have a GridView with a item template defined like:

public class ToolLogTemplate : ITemplate
{
    public String DataField { get; set; }

    public ToolLogTemplate(String column)
    {
        DataField = column;
    }

    public void InstantiateIn(Control container)
    {
        var textBox = new TextBox();
        textBox.ClientIDMode = ClientIDMode.Predictable;
        textBox.CssClass = "ToolLog";
        textBox.AutoPostBack = true;
        textBox.DataBinding += textBox_DataBinding;

        container.Controls.Add(textBox);
    }

    void textBox_DataBinding(object sender, EventArgs e)
    {
        var textBox = (TextBox)sender;
        var context = DataBinder.GetDataItem(textBox.NamingContainer);
        textBox.Text = DataBinder.Eval(context, DataField).ToString();
    }
}

The GridView is inside of a UpdatePanel defined like:

        UpdatePanel updatePanel = new UpdatePanel();
        updatePanel.UpdateMode = UpdatePanelUpdateMode.Conditional;

The TextChanged event of the TextBoxes in the GridView trigger a full refresh of the page. My understanding was that by wrapping the TextBoxes in a UpdatePanel it would trigger a partial refresh instead. Am I misunderstanding this?

Update in response to the newest comment on the question:

I have some javascript attached to the textboxes:

                currentTextBox.Attributes.Add("onFocus", String.Format("document.getElementById('RowTextBox').value = {0}; document.getElementById('ColTextBox').value = {1}; this开发者_开发百科.style.backgroundColor='#ffeb9c';", i, j));
                currentTextBox.Attributes.Add("onBlur", "this.style.backgroundColor='#ffffff'");

It just sets the colors of the textbox and saves where it is in the gridview. The updatepanel works as expected with the menu and button I have in it, it's just the textboxes that cause a full postback.

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Upon seeing update code, I have revised my answer...

The UpdatePanel needs to be told which controls it should respond to. You can do this by adding Triggers. In your case, you have TextBox controls within a GridView. These Textboxes are set to autopostback. Since they are within the GridView, I believe the GridView is treating them like a RowCommand. Using your original code, I would recommend you add the following:

UpdatePanel updatePanel = new UpdatePanel();
updatePanel.UpdateMode = UpdatePanelUpdateMode.Conditional;

gridView.OnRowCommand = "GridViewRowCommand";

AsyncPostbackTrigger newTrigger = new AsyncPostbackTrigger();
newTrigger.ControlID = gridView.ControlID;
updatePanel.Triggers.Add(newTrigger);

Within your codebehind, you would need to do something like this:

protected void GridViewRowCommand(object sender, RowCommandEventArgs e)
{
    var myTextBox = e.Row.FindControl("myTextBoxID");
    // Do some work
}

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Well unfortunately I was never able to make the model described here work. Instead I put an invisible button inside of the updatepanel and had javascript click it on the textboxes onchange event. I don't know why this method works and the TextChanged one doesn't, but that's how it ended up going down.