I added a custom aspx page, it works but my custom master page is not being applied.
My master page resides in site collection only, so I am trying this flag to custom aspx page,
<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="AddBlue.aspx.cs" Inherits="MyWeb.AddBlue"
MasterPageFile="~/sitecollection/_catalogs/masterpage/masterpages/mycustom.master" %>
But I am getting this error,
The file '/_layouts/15/MyWeb/~sitecollection/_catalogs/masterpage/masterpages/mycustom.master' does not exist.