For Expire Date. If date come to expire then before 1 week system should give Alert message.

//global declaration

public static string d1 = DateTime.Now.ToString("dd");
public static string d2 = DateTime.Now.AddDays(8).ToString("dd");

    //page_load
    int span = Convert.ToInt32(d2) - Convert.ToInt32(d1);

    if (span == 8)
    {
        ScriptManager.RegisterStartupScript(Page, this.GetType(), "alert", "window.alert('You have only one day to expire support');", true);
    }
    else
    {
        ScriptManager.RegisterStartupScript(Page, this.GetType(), "alert", "window.alert('You have expire support of this contract');", true);
        return;
    }