Dynamically Created checkbox doesn't fire event on click C#

I am creating checkbox dynamically and adding the checkbox to dynamically created Gridview. I am assigning event to checkbox for checkChanged event but event doesnt fire on clicking. Here is the code:

public class AddTemplateToGridView : ITemplate
{
    ListItemType _type;

    string _colName;

    public AddTemplateToGridView(ListItemType type, string colname)
    {
        _type = type;
        _colName = colname;
    }
    void ITemplate.InstantiateIn(System.Web.UI.Control container)
    {
        switch (_type)
        {
            case ListItemType.Item:
                CheckBox tb = new CheckBox();
                tb.DataBinding += new EventHandler(tb_DataBinding);
                tb.AutoPostBack = true;
                container.Controls.Add(tb);
                break;
        }
    }
    void itemChanged(object sender, EventArgs e)
    {
        string t = "item changed";
    }
    void tb_DataBinding(object sender, EventArgs e)
    {
        CheckBox tbx = (CheckBox)sender;
        tbx.CheckedChanged += new EventHandler(this.itemChanged);
    }
}

I am using ITemplate to create checkbox to add them to duynamically created GridView, Here is code of Gridview:

GridView gv = new GridView();

                    TemplateField f = new TemplateField();
                    f.ItemTemplate = new AddTemplateToGridView(ListItemType.Item, "Add/Remove");
                    gv.Columns.Add(f);

                    gv.Enabled = true;
                    gv.AutoGenerateColumns = true;
                    gv.CssClass = "table table-bordered table-striped";
                    gv.DataSource = data;
                    gv.DataBind();
                    gridsPlaceholder.Controls.Add(gv);