Change ASP.NET Core from npm to Yarn

Over the past couple of months, I have been having some issues with npm. Between the upgrading of npm Windows begin a pain and a version incompatibility with node I have just gotten frustrated with it. This post is going to cover the steps to use Yarn as a replacement for npm in an ASP.NET Core application.


The first step is to get Yarn installed. Head over to this site and download and run the installer for your operating system.

For Visual Studio, Mads Kristensen created an extension for Yarn that makes the integration much better. The installer for the extension can be downloaded from here.


Open a command prompt in the same directory as your project’s  package.json file and run the following command.

This will create a  yarn.lock and lay out the  node_modules folder using Yarn’s resolution algorithm.

I did hit the following error when I did the  yarn command. I left out the specific file that it had an issue with because I am sure yours would be different.

To clear the issue I just deleted the  node_modules directory and let Yarn recreate it. It might also work to use a command prompt with administrator privileges.

Visual Studio

With the Yarn extension installed there are a couple of settings that are helpful to change. All the setting we will be changing can be found under the Tools > Options menu. The first is to have  yarn install run when the  package.json is saved. Look under  Web > Yarn Installer for this option.

The second setting is to turn off automatic NPM restore so packages are restored twice. This requires the options under NPM to be set to false. The options can be found in  Projects and Solutions > Web Package Management > Package Restore.

The extension helps with Yarn integration, but the integration still isn’t as full-featured as using NPM. At my current level of frustration having to manually restore package when I open a project on a new PC is totally worth it.

Wrapping Up

So far Yarn has been great and I have not hit any issues, but my usage has also been limited. It seems like a solid alternative to NPM.

Make sure and check out Yarn’s official post on migrating from NPM which can be found here. Of specific interest will be the CLI command comparison which can be found here.

Auth0: Usage from Angular

This post is a continuation of my exploration of using Auth0 with ASP.NET Core with an API and an Angular front end. I recommend you start with the first post if you are new to Auth0.

This post is going to add a login from Angular in the Client Application as well as accessing the API once logged in. The starting point of the code can be found here.

API Application

To give us an endpoint in the API to call let’s move the  SimpleDataController class from the  ClientApp/Controllers directory to  ApiApp/Controllers directory. Also, remember to adjust the namespace to reflect this move.

To remove some complication we are going to add a CORS policy to the API Application to allow all CORS request. This wouldn’t necessarily something I would recommend for a production application. For more information on CORS check out this post.

To add the CORS policy open the  Startup class and add the following to the  ConfigureServices function which adds a CORS policy to DI that allows all calls through.

Next, in the  Configure function, CORS needs to be added to the HTTP pipeline with the policy added above. The following is the full function body for reference, but only the CORS line is new.

Note that the API isn’t currently using Authorization at all and won’t be for this post.

Client Application

Instead of redoing a lot of the same work that I covered in some of my posts on using Identity Server and Angular together I decided to copy the ClientApp directory and use it as a starting point. The rest of the client changes are going to assume the same starting point which means we will be using angular-auth-oidc-client instead of the Auth0 client to do the Open ID Connect bits.

Configuration values from appsettings.json

We need some setting from the ASP.NET Core part of the client application. First, add the following new settings to the  appsettings.json file.

Next,  Index.cshtml needs to be changed to provide some prerender data. The following shows the new data being passed into the Angular application (this post covers this in detail).

Now that the prerender values are being passed in we need to handle them in the  boot.server.ts file in the  createServerRenderer export. The following is the full list of values.

Down a bit in the file, the  setImmediate call needs to be changed to the following.

Next, in the  app.module.browser.ts file we need functions for getting the config values as well as the associated providers. The following is the full file without the imports.

Finally, in the  auth.service.ts file we need to inject the new configuration values. The following is the constructor that takes in the new values as well as uses them in the set up of the  OpenIDImplicitFlowConfiguration.

Make sure in the Auth0 client setup you allow the callback listed above or you will run into issues.

Wrapping Up

Working on this post further convinced me that Open ID Connect is the way to go. I basically took an implementation that was meant for Identity Server and used it with Auth0.

Make note that the reason the API is unsecured at this point is that I had an issue getting angular-auth-oidc-client to play nicely with Auth0 for some reason. I doubt it is an issue with either product just some sort of missing configuration on my part. This is the part of the post that I sunk so much time on. In the end, I decided to just skip it for now. If anyone does get that setup work I would love to see the sample so I know what I was doing wrong.

The completed code can be found here.

Identity Server: Upgrade Client to Angular 5

I have been working a lot on my basics sample project to explore some new client-side frameworks (React and Vue if you are interested). Since I have been away from the Identity Server sample for a while I thought it would be good to see what updates the project might need. It turns out that Angular was the big thing that was out of date. This post is going to cover the changes to get the project updated to Angular 5.


In the Client App project open the  package.json file and update the version of the  @angular packages to at least the following version, and of course feel free to pin the exact version. I don’t just because of the nature of this sample.

At this point, I tried to run and got an error about the version of  rxjs being used. Instead of just blindly going package by package and seeing which versions were required I installed the Angular CLI and created a new Angular 5 application and used it as an example of what version I needed. Use the following commands if you would like to follow the same process since the current versions have changed by the time you are reading this post.

The above led me to the following version changes.

Attempt 2

At this point, I tried running the application again and received the following error.

Error: Version of @angular/compiler-cli needs to be 2.3.1 or greater. Current version is “5.0.1”.

As you can imagine I was surprised that 5.0.1 < 2.3.1. Turns out this is related to the version of @ngtools/webpack. This package deals with ahead-of-time compiling which my sample application uses, but the application I generated using the Angular CLI doesn’t. Updating to the following version cleared up the issue.

Open ID Connect Client

There was a much new version of the Open ID Connect Client that the Angular application is using so I upgrade it as well to the following version.

This version dropped the  startup_route so the following line had to be removed from the  AuthService class.

Final Steps

Now that the package versions are sorted run the following commands from a command prompt to make sure that all the new version are installed and in the proper places.

Wrapping Up

I am glad to have this upgrade done. It seems that every time I do one of these upgrades I end up down some rabbit hole. On the plus side, I seem to be getting faster at resolving the rabbit hole issues, or the frameworks have made a lot of progress on making sure the upgrade processes are simpler than they used to be. Either way, I get to expand my knowledge. I just need to schedule a bit more time before attempting upgrades.

The code in its finished state can be found here.

Vue: Contact Detail

Last week’s post covered adding a Vue project to the ASP.NET Core Basics example solution. This post is going to cover adding a read-only view of a contact’s detail to being the Vue sample a step closer to being in line with the Angular, Aurelia and React samples. The code before any changes can be found here.

Contact Class

The  Contact interface in the  contactlist.ts file should be deleted. Add a  contact.ts file to the  ClientApp/components/contacts/ directory. This will hold the replacement for the interface we just deleted. The full class definition follows.

This class is very simple and will be used later to show how a function call can be used as part of a view.

Contact Service

Since the application will now have two places that need to access the ASP.NET Core API lets to refactor the API access into a service. This is the same style used by the Aurelia, Angular and React applications. Add a  contactService.ts file to the  contacts directory. The service will provide functions to get all contacts or a single contact an ID. The following is the full class.

Now the API access in the  ContactListComponent can be refactored to use the service. First, add imports for contact and service.

Next, replace the fetch call with a service call.

Contact Detail Component

Add a  contactDetail.ts which will be the backing component for the contact detail view. The following is the full class. Pretty much all it is doing is using get contact service to get contact detail by ID when it is mounted.

Now add a  contactDetail.vue.html file for the UI bits of the contact detail. This is basically just HTML with the same binding syntax as before. Notice that the binding of address is a function call. The other Vue things to note are that the details will only show if contact is truthy using the v-if.

Routing with a Parameter

Finding the proper way to route with at parameter in Vue was not easy. The way it is done has evolved over time making find the right way a little challenging. The first step is to add a route for the contact detail by adding a new item to the  routes array in the  boot.ts file.

The  :id in the path denotes a parameter. The  props: true bit is also key to getting the ID when in the contact detail component. The  contactlist.vue.html needs to be updated to link to the contact detail route.

Finally, in the  ContactDetailComponent we need to use the ID. To do so we need an import to allow the use of the Prop decorator.

Now all that is needed is to apply the decorator to a property of the class that matches the name of the parameter in the route.

Now the ID can be used to get the proper contact from the contact service. The following is code that was already shown, but the full context of how the prop decorator is used is important so I am repeating it here.

Wrapping Up

This brings the projects one step closer to being on the same level feature-wise. Look for one more post to get the Vue project features lined up with the other samples in the solution.

Keep in mind that this is my first look at Vue and my examples may or may not be idiomatic.

The code in a finished state can be found here.

ASP.NET Core Basics: Vue with an API

In the past, I have done some exploration on AureliaAngular and React via the ASP.NET Core Basics series. This post is going to take a similar approach using Vue. The code for the project will be in the same repo as the previous basics examples and will be utilizing the same API to pull data. The code before adding the Vue project can be found here.

Project Creation

There is not a template for Vue built into Visual Studio, but there is a set of templates that can be used via the .NET CLI with the  dotnet new that includes Vue (as well as Aurelia and Knockout). A full list of available templates can be found here. The template we need is Microsoft.AspNetCore.SpaTemplates and can be installed using the following command from a command prompt.

Create a Vue folder at the same level as the other projects, for the samples this would be in the  src folder. In the command prompt navigate to the  src/Vue/ directory. Run the following command to create the Vue project.

After the project generation completes run the following to get the needed npm packages installed.

The last step is to get the new project added to the existing solution. Navigate the command prompt to your solution file. For the sample project, this is the root of the repo. Then run the following command (this could also be done through Visual Studio instead of using the CLI).

Adding the Contact List

In the  ClientApp/components directory add a new  contacts directory to house all the awesome contact related functionality we will be adding. Next, add a new  contactlist.ts. To this new file add the interface which defines what a Contact looks like.

Above the contact interface, add the following imports needed to create a Vue component.

Finally, add the contact list component. This component maintains a list of contacts which gets filled from our existing API when the component is mounted (see the docs for more information on Vue’s lifecycle hooks).

The following if the full component just to provide full context.

Next up is the UI for this contact list component. In the same directory add  contactlist.vue.html.  The following is the full file.

All of the above is pretty straightforward. All the Vue specific items have a  v- prefix.

Add the Contact List to Navigation

The last bit needed to have a working contact list is adding it to navigation so the user can get to the list. The routes are defined in the  boot.ts file in the  routes array. Add the following line to the array to handle our contact list.

Now that the router knows to handle the contact list it needs to be added to the navigation UI. Open the  /navmenu/navmenu.vue.html file and find the unordered list that is the navigation menu. Add a new list item to provide a link to the contact list.

Wrapping Up

Vue reminds me a lot of Aurelia in its simplicity so far which is awesome. Look for the same progression of posts for Vue that happened with React over the last few weeks.

The code in its final state can be found here.

React: Form for Contact Add

Last week’s post covered adding a read-only view of a contact’s details. As before the goal is to get the React project’s features in line with the Aurelia and Angular samples. This week we will be adding a form to all addition of a new contact. The code before any changes can be found here.

Contact List

On the contact list page, we need to add a link to create a contact. This will be added just after the header in the  ContactList.tsx file.


In order to stay in line with the other sample, the  ContactDetail component is going to be handling both the read-only view and the view to add a contact. This means the ID that is currently part of the contact detail needs to be optional. The following is the change to make ID optional by adding a question mark.

Contact Service

In the  ContactService class, we need to add a  save function. This new function will make a post request to the contacts API and return the new contact with the ID from the API to the caller.

Contact Detail

The  ContactDetail class is where most of the changes are. I had some trouble getting React’s forms to work directly with the instance of the contact class and ended up just storing the parts of a contact directly in state instead of as an object. I expect this is a failure on my part and not an issue with React. I may revisit this in the future. Below is the new structure of the state used by contact details.

Next, the  constructor needed to be changed to handle the new state structure and to handle being called without an ID.

Again, this is way more code than it would be the contact class were being used. Next, the render function needs to be adjusted to render the UI for the read-only view or the contact creation. The decision is based on the ID being set or undefined.

The render of an existing contact needs to be changed to use state instead of an instance of a contact.

The following is the render of the add contact UI. I will call out a couple of parts after. The bulk of the code is just rending of the form.

The following is the input for the contact’s name.

Since I decided to go with the controlled component route React will be responsible for being the source of truth, not the form its self. To accomplish this it is important that the input has a  name and an  onChange event handler set up. The following is the  handleChange function which uses the name from the on change event to update the proper property in the component’s state.

The following line is the reset button which will reset the state to blank out all the fields in the form.

<button className="btn btn-danger btn-lg" onClick={() => this.reset()}>Reset</button>

The  reset function just uses  setState to blank out all the fields.

Not surprisingly the submit button triggers a submit of the form. What happens on submit is defined in the opening form tag.

The  handleSubmit function takes the contact information in state and uses it to create a new instance of a  Contact which is then passed to the  ContactService to be saved. The service returns a new contact object from the server and the ID is stored to state.

If the server does return an ID for the new contact then the  redirect is set to true. Then will case the following code to run in  renderNewContact which will redirect the user back to the read-only view of the new contact.

Wrapping Up

This pretty much gets the React application in line with the Aurelia and Angular sample applications. It has been fun getting a handle on the very, very basics of React. While I am back in the basics sample projects I may go ahead and tackle a Vue sample next.

The finished code can be found here.

React: Contact Detail

Last week’s post covered adding a React project to the ASP.NET Core Basics solution. As I stated last week the goal is to get the React project’s features in line with the Aurelia and Angular samples. This week we will be adding a read-only view of a contact’s details. The code before any changes can be found here.

Contact Class

The  Contact interface in the  ContactList.tsx should be deleted and in its please we will add a  Contact class. As part of this change, I also moved the contact related items to a contact directory. Add a  contact.ts file to the  ClientApp/components/contacts/ directory with the following contents.

This class is very simple and will be used later to show how a function call can be used as part of rendering.

Contact Service

Since the application will now have two places that need to access the ASP.NET Core API I decided to refactor the API access behind a service. This is the same style used by the Aurelia and Angular applications. Add a  contactService.ts file to the  Contacts directory. The service will provide functions to get all contacts or a single contact using its ID. The following is the full class.

The final step in this refactor is to use the new service in the  ContactList class. First, add imports for the service and  Contact class.

Then, replace the fetch call with the service.

Contact Detail Component

Add a  ContactDetail.tsx file which will be used to show the details of a contact including using the  getAddress function of the  Contact class. The following is the full contents of the file.

This is all very similar to the things I have covered before. Now that we have a contact detail component we need a way to display it.

Routing with a Parameter

Import the contact detail in the  route.tsx file.

Next, add a route path for contact detail that expects an ID.

Back in the  ContactList component change the ID to be a link to the new contact detail route using the ID of the contact.

The code for pulling the route parameter was in the  ContactDetail component above, but I am going to show it again just so all the route with parameter information is together. The route parameters can be accessed using  props.match.params.{parameter name} which in this case ends up being The following is the constructor of the  ContactDetail component which is using a route parameter.

Wrapping Up

This brings the projects one step closer to being on the same level feature-wise. I expect at least one more post to get the project features lined up so make sure and keep a lookout for the next post.

Keep in mind that this is my first look at React and my examples may or may not be idiomatic. So far I am really enjoying working with React.

The code in a finished state can be found here.

ASP.NET Core Basics: React with an API

In the past, I have done some exploration on Aurelia and Angular via the ASP.NET Core Basics series. This post is going to take a similar approach as I start doing some exploration with React. The code for the project will be in the same repo as the previous basics examples and will be utilizing the same API to pull data. The code before adding the React project can be found here.

This post is going to cover adding a React project to the existing using the React template that is now built into Visual Studio. The same thing can be accomplished using the .NET CLI so don’t feel like Visual Studio is required. The goal for the React project in this initial post will be to connect to the contacts API and download a list of contacts and render that to the screen. In future posts, I hope to expand this functionality to match that of the Aurelia and Angular projects.

Project Creation

Right-click and select Add > New Project.

In the Add New Project dialog select the ASP.NET Core Web Application. In the case of the sample, the project will be named React. Click OK to continue.

On the next screen make sure and select ASP.NET Core 2.0 and the React.js template. Then click OK.

The following is the resulting React project in the context of the full solution.

Next, make sure and run npm install from a command prompt in the React project’s directory to ensure all the npm packages get restored.

Adding the Contact List

Inside the  ClientApp/components/ directory add a file name  ContactList.tsx. TSX is the TypeScript version of the React JSX file type. The official docs on JSX can be found here. Since this is my first time working with React I took the  FetchData.tsx file and copied the contents and used that as the starting point for my contact list. To lead with there is an interface for what should define a contact.

Next, we have an interface for the state of this component with contains a loading flag and an array of contacts.

In the constructor for the component is where the data is pulled from the API using  fetch. The data from the API is then saved to the state of the component using the  setState function.

Next, the component has a function named  renderContactsTable which takes an array of contacts and returns how they should be rendered. In this case, the contacts are rendered to a table that displays the contact ID and Name.

Finally, there is the render function. As you can guess this is what gets called to render the component. In this case, either “Loading” or the contact list gets displayed depending on if the contact list data has been loaded or not.

The following is the full file for reference.

Add Contact List to Navigation

Now that we have the contact list component it needs to be added to the navigation menu. The first step is to add it to the application’s router. This can be found in the  routes.tsx file. The file is short so I am going to include the full content. Lines 7 and 13 are the ones added to handle our contact list.

The last change is to add a navigation link to the  NavMenu found in the  NavMenu.tsx file. As I am sure most of us are used to adding an item to the nav menu is just adding a new li, but with the React specific  NavLink bit.

Wrapping Up

React is different than both Aurelia and Angular. Don’t take that as a good or bad thing. I don’t plan to pick on a side on the Angular vs React debate I just want to get a good feel for the different frameworks. So far the React experience has been pretty nice and I look forward to doing more exploration.

You can find the finished code for this post here.

Pass ASP.NET Core Appsettings Values to Angular

As part of getting my set of Identity Server 4 sample applications to run in Azure, I needed a way in the Client Application to pass some configuration values from  appsettings.json to the Angular front end that could be used both during server-side rendering and client-side rendering. This application is using JavaScriptServices. This solution may need tweaking if your application isn’t using JavaScriptServices. The code for the client application can be found here.


In this example, we need to pass the address of our Identity Server and API from  appsettings.json to Angular. The following is the settings file for this example.

Providing Configuration Data to Angular

In this application, Angular is loaded from the index action of the home controller. This view can be found in the  Views/Home folder in the  Index.cshtml file. The following is the file before any changes.

The first change needed is to inject the configuration data using ASP.NET Core’s DI system. Add the following two lines at the top of the file.

Now the configuration data from the application is available to this view. Next, we need to pull a couple of values out of the configuration data and pass it to the Angular application. To do this we are going to use the  asp-prerender-data tag helper. You can read more about it in the official docs. The idea is you construct an object which is then serialized and stored in In our example, we are passing the URLs for the Identity and API Applications.

The above is creating a new object with an  apiUrl property and an  identityUrl property. The following is the full completed view for reference.

Angular Server-Side Boot

When Angular gets prerendered on the server-side it runs the code in the  boot.server.ts file. This is where we will set up the providers needed on for the server side prerender. This is the bit that I missed for the longest time when trying to get this example going. I kept trying to find a way to add the providers in the  app.module.server.ts file. Add any providers you need to the  providers constant. For example, the following is passing URLs for an API and Identity Server in addition to the defaults provided by JavaScriptServices.

Lower in the same file we can pass through the configuration values to the client side render as globals on the window object. To do this add a  globals property to the object being passed to the  resolve call.

The above will have the URLs as part of a single object, but you could have each URL as its own property if you prefer.

Angular Client-Side

Now that the server-side has providers for API URL and Identity URL we need to provide the client-side with the same capabilities. These changes will be in the  app.module.browser.ts file. The first step is to add providers for each.

Next, we need functions to return the URLs from the  url_Config property of the window object which the following two functions do.

Wrapping Up

With the above, you can now use your configuration values from ASP.NET Core and pass them through to your Angular application. In hindsight, the process is pretty simple, but getting to that point took me much longer to figure out than I would like to admit. I hope this post saves you some time!

JavaScriptServices: What happen to Aurelia, Vue, and Knockout Templates

With the release of Visual Studio 2017 version 15.3 there are now built in web application templates for Angular, React, and React and Redux.

This is an awesome addition and makes creating new applications with the most popular frameworks simple. What do you do if your framework isn’t one of the top 3 options? JavaScriptServices can help out here and has provided templates for Aurelia, Vue, and Knockout in the past.

Where have they gone?

This is where it gets a little tricky as the templates still exist and are still being maintained, but finding them is a little harder at the moment for some reason. Yeoman was how JavaScriptServices was used in the past, but that has now transitioned to using the .NET CLI and can be added using the following.

After that is complete you will see a list of templates that are now available.

Now you can create an Aurelia project using the following command.

Wrapping up

I was very happy to see that support for the other frameworks hadn’t been dropped. There are a ton of other templates available for dotnet new which can be found here.