What is an asynchronous programming in terms of c#?

GetAll method of the repository class, which is also marked with the async keyword and uses the await keyword to asynchronously fetch the data.

Each of these state machines is responsible for managing the asynchronous execution flow of the corresponding method. When you call GetAllData method, the first state machine is created and used to await the completion of the second state machine in the _repository.GetAll() method.
While it is true that using await multiple times can result in the creation of multiple state machines, this is not necessarily a problem. In fact, it is a common pattern in asynchronous programming to use await to compose multiple asynchronous operations together.
However, it is important to keep in mind that each state machine comes with some overhead in terms of memory and processing resources. Therefore, it is important to use asynchronous programming judiciously and avoid unnecessary await expressions.

How can I modify it so that compiler awaits and creates a state machine only once

You can modify the code to avoid creating multiple state machines by changing the method signatures to return Task instead of Task and using the ConfigureAwait(false) method in the repository method.
By using ConfigureAwait(false) in the repository method, you tell the compiler not to capture the current synchronization context when the method resumes after the await keyword. This means that the continuation will not be executed on the original thread, but rather on any available thread from the thread pool.
By returning Task instead of Task in the method signatures, you eliminate the need for the compiler to create a state machine for each method.
With these modifications, the GetAllData method now awaits the GetAll method in the repository without creating a new state machine. Instead, the same state machine created by the