Water Level detection

Could anyone suggest for me the components needed to build graduation project to measure water level and give alert when reaches specific level and this is integrated with my website (ASP.NET, C#) using SQL SERVER database.

I am very grateful for you.

Water level of what (river, septic tank, cup of water)?

If this is a graduation project, then you should only be asking for the final details of YOUR project.
Not to do the project for you.
Post what you have done so far, and why it isn't working the way you want it to.

I am using a beaker of 30 cm height, my project is a website and this is a complimentary part, I need only the name of components because this is Engineering parts, for coding, I am able to write it if data is sent by serial communication.
Thanks people.

to measure water level

and give alert when reaches specific level

One, or the other, or both.

Measuring exact water level is not easy.
Capacitive (non-contact) measurement is needed for a permanent setup.

If only one level is needed, then use a float switch.
There are also multi-level float switches.
Google it.

Take a look at this example. It does not measure the water depth. It measures the distance from thr sensor to the water level. So, since you know the size of the beaker, you should be able to figure out the math.

To get thr data to your website, take a look at this example to create a REST API which you should be able to call from your ASP.NET | Open-source web framework for .NET code.

This is a 30cm tall beaker.
I doubt that 40kHz ultrasound would work there.

So many ways...
Level switches (mechanical float switch on the inside or capacitive on the outside of the cup), ultrasound (from above, measure where the surface is), pressure (at the bottom of the container), weight of the container, just to name a few.

For logging the data: get a NodeMCU, connect to your local WiFi network, and write your stuff directly to a MySQL database using the MySQL connector.