I'm still struggling to understand the difference between ASP.NET Core Hosted and Server-side Blazor. I know same question already exists, but it's not satisfying. In fact, I couldn't find the satisfying answer anywhere - the answers were more or less the same.
If hosted option uses server (IIS, Kestrel), then why server-side? Confusing... It's a shame that official documentation didn't shed the light either...
UPDATE
The confusion stems from the fact that we have THREE options to create Blazor application. After executing dotnew new --list I get:
dotnet new blazorserver (Blazor Server App)
dotnet blazorwasm (Blazor WebAssembly App)
However, there's a third option:
dotnet blazorwasm --hosted (or dotnet blazor --hosted)
It's the same as check box in Visual Studio when creating application:
The documentation says:
you have the option of configuring the app to use an ASP.NET Core
backend by selecting the ASP.NET Core hosted check box
But no explanation was provided what does it mean...
Re this part of your question:
However, there's a third option:
dotnet blazorwasm --hosted (or dotnet blazor --hosted)
It's the same as check box in Visual Studio when creating application:
The
documentation
says:
you have the option of configuring the app to use an ASP.NET Core
backend by selecting the ASP.NET Core hosted check box
But no explanation was provided what does it mean...
TL;DR
'Hosted' is used where you want the back-end of your site and the Blazor client using that back-end to both be hosted on the same website.
In Detail
I agree, the documentation really isn't terribly clear about all of this, but the explanation is actually simpler than it seems:
The Blazor app has to be 'hosted' somewhere
The first thing to remember is that the Blazor WebAssembly 'app' is not a standalone website, it's an app that's embedded in a website. In a lot of cases it will behave like a website, because it will be used as a Single Page Application, but that is by no means required.
Essentially the Blazor WebAssembly app is a series of files and a JavaScript file that are created by compiling/publishing your Blazor project.
Those files then need to be put on a website somewhere and the combination of the name of a div tag and the Blazor JS file produced for your site deals with wiring your app files into the WebAssembly part of the browser so that it's then rendered on the page.
The key here is that the website 'hosting' your Blazor app does not have to be an ASP.NET Core site. It could be any site, pure HTML, Drupal, whatever, it just needs to be shown on a browser that handles WebAssembly and JavaScript correctly.
However, if you're also writing the backend of your site in ASP.NET Core, you can reuse that site
So, your Blazor project doesn't have to be hosted in a website written in ASP.NET Core, but it does have to be hosted somewhere (so the user can see it).
If you're also writing the back-end of the site at the same time, e.g. if you're writing an API or SignalR hub to send and receive data from your Blazor client, and if you're writing that back-end in ASP.NET Core, then you can reuse that same site to also host your Blazor client.
This scenario is what the 'Hosted' option is for.
If you create a project using the template in the screenshot above, with the 'hosted' option ticked, you'll see that the [YourProjectName].Server project that's created is the Start Up project, but the index.html page that's shown when you run that project has come from the [YourProjectName].Client project.
This approach means you only have one site running on your server (which could be good or bad) and also means you won't run across any CORS issues.
But you don't have to have an ASP.NET Core site at all
If your Blazor site is a standalone site that doesn't read/write from any server, or if it only talks to 3rd party APIs or an existing Web API running on the older .NET Framework, then you don't actually need an ASP.NET Core site at all.
In that case you don't use the 'hosted' option.
Instead, you can simply publish your Blazor project and then take the files from the release folder and host them in any site.
Update
I see where you are coming from now. The confusion stems from the fact that you have an option called --hosted when using the client-hosted Blazor. This options means having Blazor to include ASP.NET Core runtime.
Why this option? Because you can write an offline app (e.g. calculator app) that does not need any kind of connection to external services, making ASP.NET Core irrelevant. However, you might want to write an online app that accesses online DB, external APIs, do verification, etc. For these kind of apps, you will need an ASP.NET Core stack to support your app.
Check this FAQ: https://github.com/aspnet/Blazor/wiki/FAQ#q-can-i-use-blazor-with-aspnet-core-on-the-server
Original answer
They are two hosting models: server-hosted, and client-hosted.
The difference is whether the app is hosted in server, or in client. Server hosting means your app logic runs in the server (you can think of it similar to what Web Forms is), you click on a button, an "Ajax" call sends the request, the server receives the request, and sends back the updated page. However, here it uses SignalR not Ajax, which is a low level socket communication (read efficient). And instead of updating a whole page, it updates only the relevant parts (thus it is a single page application).
On the other hand, client hosting means your logic runs within the browser. Think of it as if your C# logic is converted into JS, and it is embedded in the page. So the logic runs in the browser. This is possible after the introduction of WebAssembly which you might want to read about.
Let's say you want to create a calculator app. Your server hosted app will then need to communicate with the server to calculate and get the result for each calculation, while the client hosted does not need, and calculates the result in browser.
You might wonder, why we have two options. The reason being that support for WebAssembly (which a client hosted app relies on) is either incomplete or non-existant in many browsers, and performance differs widely too.
https://caniuse.com/#feat=wasm
The question is about the option "ASP.NET Core hosted" in Visual Studio, while creating a new Blazor Project with Blazor WebAssembly App.
Selecting this option scaffolds out 3 Projects for you (vs 1 WebAssembly project, if this option is not selected)
Server Side Blazor Project
Client Side Blazor Project (WebAssembly)
Shared project for shared entities between Server and Client Projects.
With this option you can have
Blazor WebAssembly only option for sections of your project where the logic can execute in browser.
Server hosted option where all the processing is done on server and only HTML is rendered onto the browser.
When deployed, all these projects go to the same location. So if you have a requirement for both Server Side as well as Client side options, then go for it.
I too had the same confusion while reading the documentation. But it was explained in Blazor webassembly section
dotnet blazorwasm - is a standalone project
dotnet blazorwasm --hosted (or dotnet blazor --hosted) - is a projected hosted with ASP.NET Core backing API's.
A hosted deployment serves the Blazor WebAssembly app to browsers from an ASP.NET Core app that runs on a web server.
The client Blazor WebAssembly app is published into the /bin/Release/{TARGET FRAMEWORK}/publish/wwwroot folder of the server app, along with any other static web assets of the server app. The two apps are deployed together. A web server that is capable of hosting an ASP.NET Core app is required. For a hosted deployment, Visual Studio includes the Blazor WebAssembly App project template (blazorwasm template when using the dotnet new command) with the Hosted option selected (-ho|--hosted when using the dotnet new command).
Here are my two cents.
Create a Blazor WebAssembly App with ASP.NET Core Hosted check box selected.
Once created observe the project references.
Note that the server project references client project.
I had this same confusion as others, that the client calls the server, and that they are two independent Visual Studio projects. So this project references puzzled me.
The fact is client project is hosted by and served by the server project. When we want to run the app, we need to run the server project and not the client project.
So when you want to run the Solution(App), you must ensure to set the Server project as the startup project and not both the server and client. Due to my initial misunderstanding, I was setting multiple startup project, thinking that the client(something like React App) calls the server(WebApi), and that they both should be running simultaneously, for the client to call the server.
The above is correct, but the following is INCORRECT.
If you do that, you get the following error, and this stung me.
Microsoft Visual Studio - One or more errors occurred. Failed to launch debug adapter error
And finally if you are thinking to dockarize by adding docker files and docker-compose files for different kinds of Blazor apps, do take a look at this github repo.
Specifically for this kind of apps that we are talking about take a look at this and this folder in that repo.
Blazor-WASM
The application can work offline after the first loading. As an Example If you make Loan calculator with Blazor WASM, you can send all the data, business logic and validation to the client side in the first load like loan types, loan rates, max repayment period like that then because of the logic also in client side, it don't need do the communication with the server again and again when you change the loan type or repayment period because business logic in client side using the user selected data Blazor can render the UI and show the result.
Blazor-server
Application use server to render the UI so as on the Loan application if user change the loan type blazor send that user change value to server using SignalR and in the server has data and the logic for get the result, after that server render UI and send UI changes to the client side using SignalR and redraw the UI in clients screen.
Blazor-ASP.NET Core Hosted
Visual studio generate 3 projects in the core hosted template
ClientProject - this is a Blazor-WASM application
ServerProject - this is a .NET CORE API
SharedClassProject - this is a class library that holds shared
objects between client and server
As the loan example in the first load loan types and calculation logic are loaded in client side.
If the user selects the loan type Blazor creates an http call to the API application to get the loan rates according to the selected loan type if the interest rate is in the db.
Then the user enters the repayment period because of calculation logic in the client side. Now the application can calculate the result and render the UI to show the result. So with this model you can keep some data or logic in the server and other data or logic on the client side.
I have come into a new company to upgrade a large web application. Yes it is a Web app not a Web site and I am using Web forms.
It is quite old and I would say poorly written. The PM wants to have it cleaned up and ported to C#. The issue here is that it is constantly changing and updates will still be working whilst I work on it.
The current plan is to create a new home page launcher in a new UI (c#) so that the upgrade is coming. Rewrite certain sections at a time and release as we go. The launcher currently actually launches new pages in a new browser window so I do think this is feasible.
However, so my question is can this be done. I've read a number of threads that it is possible with web sites but not with web apps. If this cant be done is there a solution where I can run my web app and launch windows in the older app. Desirably having the two different web apps in the same solution?
We have rewritten a WinForms app A as a web app. The old WinForms app had integration with WinForms app B, in that you could fire it up from app A with a set of variables.
Users are now demanding the same functionality from a rewritten web app. My first thought was for WinForms app B to create my own URL protocol (foo://...), but it seems that to do that you have to create keys in HKEY_CLASSES_ROOT - which is an activity done by an admin user. However, the users are basically limited users and WinForms app B is actually a ClickOnce app.
What are my options?
Since App A is now in the cloud and the user interacts with it via the browser, it is sandboxed and many of the things that a desktop app can do are not available to it anymore.
This is a security feature and outside of writing a browser plugin that will bridge between App a on the browser and App b, there isn't much you can do.
I've a general design question:
I have a mailserver, written in C#.
Then I have a web forum software, written in for ASP.NET in C#.
Now I'd like to integrate the mailserver into the ASP.NET forum application.
For example, I'd like to make it possible that one can create a mailinglist from the forum, and give users the oportunity to add oneselfs to the mailinglist members in the forum, and then add the new list-members to the respective mailinglist on the server.
Since the server is a separate console/winforms/service application, I first thought I'd best use .NET remoting for this.
But my second thought was, that some users might host their forum on a host where
(a) they don't have a virtual machine where they can do what they want
(b) the admin of the host might not want to install an additional mailserver or charge extra for this
(c) the user might have a service plan that only permits to add a web-application, not external programs (very likely)
Now, I wanted to ask:
Is it possible to fully integrate a mailserver into an ASP.NET application somehow ?
(I have the full source of the server + ASP.NET application)
Well, it probably won't be a page or a ashx handler, but something like a http module ?
Or what's the general way to integrate TCP/IP applications into asp.net ?
(Of course I'm assuming the respecive ports are available/forwarded - and I'll make it possible to also run it with the e-mail server as external application)
In the ideal case I'd do the following:
Set it up on your own server(s) and expose a WCF/web service that your web app will/can interact with.
If you can't or don't want to afford to keep it running on your own, you could then charge a subscription fee for it.
It's probably not a very great idea, but you can start a thread in Global.asax and do background processing while the application pool is running/the web app is not reloaded. So you could start your server there, but you have no control over the lifetime of it
Adding to chris166's comment... you also wouldn't get control over when the application is started. [Since the application won't be loaded until a page is requested...] Its probably a better idea to setup some sort of integration between the web app and the console/service app.
I'd probably tend towards setting up a near-realtime integration where the mailserver polls the forum app for requested changes.
I have an existing ASP.NET web application that I'm converting to MVC 1.0. The site started out with one goal. However, over time our sponsors are asking for more functionality and it is obvious that MVC would be our best route due to the new requirements. I've dabbled in MVC over the last couple of months and have a pretty good grasp on it all works. The problem that I'm faced with now is that the meat of our existing web application makes extensive use of a 3rd party tool that only works within ASP.NET WebForms.
The solution that I'm working on is to have two web applications running on the server. The one application would be our existing WebForms app and is solely used to expose the above mentioned 3rd party tool's functionality. The other application will be our main portal that will act as the new site. When the user wishes to interact with the 3rd party tool, I want to be able to load an iFrame on the appropriate Views that links the user to the other application and will then allow them to interact with the WebForms site. Does this sound crazy?
The number 1 problem that I'm faced with right now is how to configure my solution make the MVC application talk to the WebForms application. Every time I run the solution, a different port number is assigned to the two applications and I can't figure out how to configure my iFrame "src" properties correctly. Of course, I can't add the WebForms application to my MVC applictions' References, so I'm stumped!
Any help would be greatly appreciated...
If the port issue is the only problem, you can run both of them in IIS under a fixed virtual application.
But the ASP.NET development server also has the feature to fix the port to a specific number and not randomize it each time.