How to connect QuickBooks Desktop using Web Connec

I'm trying to develop a simple webform application to create/edit invoice from a .aspx page and want to sync QB Desktop & MS SQL database using web connector & .ASMX web service (2 way sync: QBD -> web app & web app > QBD).

Here is a what I did:

I've setup QB Desktop US version 19 (latest) and Web connector
Added an application via adding .QWC file (I'm using this default .qwc file without any changes, not sure even how can I make it!!)

Step 1 & 2, are done but looking for proper solution to start with the development part. I've referred some other StackOverflow questions and found this sample but not sure which project and version I've to choose from both of them. I'm finding some good sample applications which connects to QB Desktop & Web applications using Interop.QBFC13

I really don't have idea how web connector works and sync with my web app.

Thanks!

I'm using this default .qwc file without any changes, not sure even how can I make it!!

This ^^^ will not work. Ever. There is no "default" .QWC file -- it is specific to your application and if you're using someone else's it's guaranteed not to work.

Create your own .QWC file. Example template:

<?xml version="1.0"?>
<QBWCXML>
    <AppName>QuickBooks Integrator</AppName>
    <AppID></AppID>
    <AppURL>https://example.com/quickbooks/server.php</AppURL>
    <AppDescription></AppDescription>
    <AppSupport>https://example.com/quickbooks/support.php</AppSupport>
    <UserName>username</UserName>
    <OwnerID>{90A44FB7-33D9-4815-AC85-AC86A7E7D1EB}</OwnerID>
    <FileID>{57F3B9B6-86F1-4FCC-B1FF-967DE1813D20}</FileID>
    <QBType>QBFS</QBType>
    <Scheduler>
        <RunEveryNMinutes>2</RunEveryNMinutes>
    </Scheduler>
    <IsReadOnly>false</IsReadOnly>
</QBWCXML>

Fields:

<AppName> This is displayed to the user in the Web Connector GUI
<AppID></AppID> Leave it blank
<AppSupport>...</AppSupport> Must contain a valid URL to a valid page which returns a 200 OK HTTP response when visited. Users who have technical problems will be directed here.
<AppURL>...</AppURL> Must contain a valid URL to your SOAP server, https://... if it's remote, http://localhost/... if it's local.
<UserName>...</UserName> This will match the username your SOAP server understands for authentication
<FileID>...</FileID> You can make this up as long as it follows the GUID format (uppercase HEX chars only!): {6904A826-7368-11DC-8317-F7AD55D89593}. It has something to do with DataExt elements; most simple integrations can just make this up.
<OwnerID>...</OwnerID> Same as above
<QBType>...</QBType> Specifies the type of Quickbooks you want to connect to with the web connector (ie “QBFS” or “QBPOS”)
<Scheduler>...</Scheduler> This is an optional element, use this to schedule the Web Connector to run every so often automatically
<IsReadOnly>...</IsReadOnly> Leave this set to false, setting it to true will not work.