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Check.aspx页面

　　　　 string uid = Request["uid"].ToString();        TextDataContext _context = new TextDataContext();        var query = _context.login.Where(p => p.userName == uid);        if (query.Count() > 0)        {            Response.Write("该用户名存在！");        }        else        {            Response.Write("该用户名可以使用！");        }        Response.End();