I am not very sure if JQuery-Ajax will work with Url of Master-Page.
You may try below things.
1) Check you have specified
attribute on your
Method. Someting as below.
public static string UpdatePollCount(string Data)
2) I have used "ICallbackEventHandler
" for Ajax call on Matser-Page before. You may have a look at below link for "ICallbackEventHandler
" use. In this Tip/Trick I have shown example of .Aspx page but it also works for Master-Page.
Simplifying Asp.Net Core Ajax