ASP.NET - Async - A system that syncs between two other systems - asp.net

Question

I am trying to create a system that synchronizes between two other systems' data.
I work on ASP.NET Web Forms using VB (Cannot be changed)
The main system functions will be in a form of Web API which will be triggered by a scheduled task or other events, such as a website form or a landing page.
Each of these functions call a REST API of System 1 and the REST API of System 2 , operates the data, and then calls each system REST APIs to update both sides.
I chose to use a ASP.NET Web Api 2 for the main system, and HttpClient to call the functions.
There will be hundreds of thousands of transactions per day. It is a lot! So I chose to use async/await methods for the HttpClient, (because of the many simultaneous long processing requests), but ASP.NET seems to have forced me to convert all the functions from bottom to top, including the Web Api functions and the database access to Async!
So I ended up changing all the functions to Async and in all the functions that call them I use Await for everything.
Everything seems to work. I don't know if what I did is correct, and I see there is no way to check if my functions are actually working asynchronically.
About the ConfigureAwait(False) I added it because I don't have operations that are context related. If there will be I will remove this statement. I read it is recommended to use it when it is possible. (Am I right?)
SMALL COMMENT:
Why is my solution good??? I am trying to avoid blocking the main thread by creating much more worker threads. Why is this a better solution? I am creating a lot of awaits which each one starts a worker. Isn't it a worse practice than the synchronic solution????
Can somebody tell me if what I am doing is correct and if not - please explain why or if there are other approaches to this scenario?
Here is the code for example (only the relevant parts). A little explanation of what you see:
The WebApi Controller has an Login function
The Login function calls the System1.DoSomething asynchronically
The System1.DoSomething calls the private function
System1.SetCredentials asynchronically
The System1.DoSomething also uses HttpHandler to get data
asynchronically from System1's API
System1.SetCredentials function calls MyLoginManager.GetCredentials asynchronically
MyLoginManager.GetCredentials calls the database asynchronically using DBHelper.ExecuteReaderAsync
The DBHelper.ExecuteReaderAsync function calls ExecuteReaderAsync
asynchronically and also opens the connection asynchronically using
OpenAsync() function
The WebAPI Controller
Public Class WebApiController
Inherits ApiController
Public Async Function Login() As Threading.Tasks.Task(Of IHttpActionResult)
Dim result As MyResult= Await System1.DoSomething().ConfigureAwait(False)
End Function
The System1 Class
Public Class System1
Public Shared Async Function DoSomething() As Task(Of MyResult)
Try
Using client As New HttpClient
client.BaseAddress = New Uri("blablabla")
Await SetCredentials(client).ConfigureAwait(False)
Dim response As HttpResponseMessage = Await client.GetAsync(urlParameters).ConfigureAwait(False)
... More code
End Using
Catch ex As Exception
End Try
End Function
Private Shared Async Function SetCredentials(client As HttpClient) As Task
Dim auth As BasicAuthenticationData = Await MyLoginManager.GetCredentials.ConfigureAwait(False)
Dim credentials As String = Cryptography.EncodeBase64(String.Format("{0}\{1}:{2}", auth.userName, auth.userPassword))
client.DefaultRequestHeaders.Add("Authorization", "Basic " & credentials)
... More code
End Function
End Class
The MyLoginManager Class
Public Class MyLoginManager
Public Shared Async Function GetCredentials() As Threading.Tasks.Task(Of BasicAuthenticationData)
Dim auth As New BasicAuthenticationData
Dim dbConn As String = DBConnection.GetConnection(True)
Dim q As String = "SELECT * FROM BlaBlaBla"
Using sdr As SqlDataReader = Await DBHelper.ExecuteReaderAsync(dbConn, q, Nothing).ConfigureAwait(False)
... More code
End Using
Return auth
End Function
End Class
The DBHelper Class
Public Class DBHelper
Public Shared Async Function ExecuteReaderAsync(ByVal dbConnection As String, ByVal commandText As String, ByVal params() As SqlParameter) As Threading.Tasks.Task(Of SqlDataReader)
Dim dbConnectionAsync As String = New SqlConnectionStringBuilder(dbConnection) With {
.AsynchronousProcessing = True
}.ToString
Dim objConn As New SqlConnection(dbConnectionAsync)
Dim oc As New SqlCommand(commandText, objConn)
Dim sdr As SqlDataReader
' Throws a custom exception if there is a problem
Try
Await oc.Connection.OpenAsync.ConfigureAwait(False)
sdr = Await oc.ExecuteReaderAsync(CommandBehavior.CloseConnection).ConfigureAwait(False)
Return sdr
Catch ex As Exception
End Try
End Function
End Class

Answer 1

You should add a call to ConfigureAwait(false) to any await behind any await that comes out of any controller action.
As Mister Epic said you'll loose things like HttpContext.Current if you call ConfigureAwait(false) and you shouldn't do that on controller action methods. But that also means that every time you don't you incur in context switching.
What you should do is extract the logic in controller action methods to their own methods (preferably on their own class) and pass every thing they need to do their work.
So, the only thing you did wrong was to call ConfigureAwait(false) in the controller action method.

Answer 2

Don't add ConfigureAwait in your web api project. Use it in library code.
The big gotcha is that when you call a method that uses ConfigureAwait, you'll lose your context. Your context includes important details like your session, so you'll need to ensure you capture any details from HttpContext you need before you call into library code that uses ConfigureAwait.