Demos from Article in Windows Developer
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WebWinFormsInteraction - An approach to use parts of your legacy app in a modern web app

This demo was made for an article in the Windows Developer magazine which was printed in November 2018.

The article describes an approach to migrate a huge legacy pc app to a modern web app step-by-step. To release a.s.a.p., the usage of old functionality in the new app might be a good option. Usually it's not possible to migrate code from decades within a year.

In this Demo the web client and the locally installed WinForms app communicate through a SignalR Hub which is also installed on the users computer.


Getting started

Clone this repo

  • Start Command Line Console in the directory you want to have the code
  • run git clone

Install and run Webserver for Angular App

  • Navigate (cmd) to the folder 'WebFrontend'
  • run code . to open the folder in VS Code and return to the console
  • run npm install to restore the node_modules (npm packages)
  • run ng serve

Install and run API, SignalR Hub and WinForms App

  • Navigate to the folder 'DotNetParts' and open DotNetParts.sln with Visual Studio
  • Run App by Pressing F5. SignalR Hub (Console App), WebAPI (AspNet .NetCore) and WinForms App will be started


  • Start "Old App" from the starter form.
  • Open the Web App by klicking the button top left.
  • Choose and change person in the "New Web App" and observe the synchronization in the old App.
  • Press "Edit" on the person -> the old App changes to Edit Mode and appear in front.
  • Save... Edit... Change person... close WinForms App (not the Starter Form) -> Web App logs out. Re-open old App -> Web is awailable again...
  • Close Old App window and observe web logout
  • Open a new Old App window and get logged-in on the web app again.
  • ...


In the sequence they usually grow...

  • Old WinForms App "DotNetParts.WinFormsFrontend": Old App dispatching relevant actions to the SignalR Hub and executing actions requested by the new client (notified by the hub).
  • WebAPI "DotNetPartsPersonApi": REST API shared by old and new client. In this case the data is just held in memory.
  • SignalR Hub "DotNetParts.InteractionHub": Communication centre for all frontends old and new installed on the client (with the old app). It broadcasts acitons to "the others" (other subscribed clients).
  • New Web App "WebFrontend": Angular Frontend which requests the aciton "edit person" from the old app as an example of using old code in the web.

It is...

  • an inspiration for developers having the challenge to migrate huge legacy apps to the web.
  • an example how old technologies and web can interact.

It isn't...

  • a general recipe for migrating old apps.
  • a tutorial how to secure a production app.

Check, design, protoype and challenge your situation in your environment! My article in the Windows Developer magazine (December 2018) might give your additional useful thoughts to this topic.