Sorry for this disturbing experience as there are many reasons that could have caused this ordeal.

However, it is important to take note of several factors in order to decisively identify what may have been the cause of this disturbing experience.

One of the factors that you may need to take notice is if the Microsoft Internet Information Service (IIS) shuts down when you attempt to navigate to a particular page on your website or when you attempt to navigate to a set of pages or the IIS just shuts down even when you don't make attempt to navigate to any page.

 If you take these into considerations you will see we have two scenarios to get clarified:

1. Does the Microsoft IIS shuts down when you attempt to navigate to a particular page or set of pages 

To determine this, try to navigate to another page, or add a fresh aspx and/or html page with no reference to the master page, and try to navigate to the new page from the page where Microsoft IIS works perfectly. 

If there is smooth navigation, then we can say we have a greenlight.

Although the above steps may look cumbersome and unnecessary to you, but you just have to go through it because this problem will persistent indefinitely, even up to the live server after deployment, if you don't get to the root.

In this case, it is understandable that there is an exception on the page(s) you are trying to navigate to that's causing the Microsoft IIS to shut down incessantly.

To uncover the exception, it is important to try to navigate to other pages that share the same Master Page with the page(s) that shuts down Microsoft IIS so as to know whether the exception occurs in the master page or the child page.

If it is established that it occurs in the Master Page or child page, make sure you reanalyze every line of code in the logic code file of the suspected page.

To help you identify the source of the exception, kindly try these:

 Check for Unhandled Exceptions:

Ensure there are no unhandled exceptions in your code that might be causing Microsoft IIS Express to crash. Check your event logs or debug output for any error messages.

 Verify Web.Config Settings:

Check your `web.config` file for any misconfigurations that might be causing issues when navigating between pages.

Check for Deadlock 

Quiet unfortunately, Deadlock is the major reason the Microsoft IIS shuts down incessantly and this occurs when a line of code withhold the Microsoft IIS for quiet long period without releasing the Microsoft IIS and nor giving any output.

In this case, the Microsoft IIS sees itself entangled, and which it sees unnecessary then it shuts down itself.

Actually it couldn't have been your aim to withhold the Microsoft IIS but a line of logical mistake can always cause this.

Take for example when you create MethodA() and MethodB; you make infirmed MethodA() to call MethodB() and also inform MethodB() to call MethodA() without any of the two methods giving room for exit. The page will always enter deadlock.

Another important thing is that in the case of deadlock, it is much likely to concentrate on every line of code that is tied to the Page Load, Page_Init, Page_LoadedCompleted or any other header event that is/are implemented on the page you are trying to navigate to before the sudden Microsoft IIS shutdown.

The Microsoft IIS just shuts down even when you don't make attempt to navigate to any page.

This is sincerely a more serious case and it requires sophisticated attention. In this case, you will have to be more rigorous in getting to the root of this ordeal. These are some steps to be taken:

Enable Custom Errors:

 Temporarily enable custom errors in your `web.config` to see if you can get more detailed error messages:

To enable custom error in your configuration file, do this;

<system.web>

  <customErrors mode="Off" />

</system.web>

Debugging:

Instead of just launching your website in the browser, run your website in debug mode and see if any exceptions are thrown when navigating to another page. You can do this by pressing F5 in Visual Studio or click on the debug button in the visual Studio.

Check Event Viewer Logs: 

Look for errors in the Event Viewer logs that might provide more details about why the Microsoft IIS Express is shutting down.

Microsoft IIS Express Configuration:

- Try deleting the Microsoft IIS Express configuration files:

    - Close Visual Studio 

    - Navigate to (on your computer file system) `%userprofile%\Documents\IISExpress\config` and delete the files there.

    - Restart Visual Studio and try running your project again.

Update Visual Studio:

In the case none of the above tips resolve your issue, kindly ensure your Visual Studio is up-to-date, as updates might resolve known issues with Microsoft IIS Express by reinstalling or updating your visual studio.