How to use Global.asax file to call Method

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ASP.NET

I want to after all event like textbox change or button click
i want to check any button is enable false or true

for this

#region "Button CSS"
    public void clear(ControlCollection col)
    {
        foreach (System.Web.UI.Control item in col)
        {
            if (item == null)
            {
                return;
            }
            if (item.HasControls())
            {
                clear(item.Controls);

            }
            else if (item is System.Web.UI.WebControls.Button)
            {

                if (((System.Web.UI.WebControls.Button)(item)).Enabled == true)
                {
                    ((System.Web.UI.WebControls.Button)(item)).CssClass = "buttonDefault";
                }
                else if (((System.Web.UI.WebControls.Button)(item)).Enabled == false)
                {
                    ((System.Web.UI.WebControls.Button)(item)).CssClass = "buttonDisable";
                }
            }

        }
    }
    #endregion

but call this method for all WebForms
I want to

clear(Page.Controls);

Call this method after Application_EndRequest
in global asax file
How to do that or any other solutions

if button Enable true i have set CSS for that and False another CSS