Calling C# function from javascript in Dot Net Core/DotNet is not defined

Question

So I'm relatively new to Dot Net Core stuff so bear with me.

My end goal is to call C# code from Javascript code in my project and vice-versa. So if there's a simpler way than what I'm doing then that would be awesome. I'm trying to follow the tutorial here to run a C# function from js:

https://learn.microsoft.com/en-us/aspnet/core/blazor/call-dotnet-from-javascript?view=aspnetcore-3.1#static-net-method-call

The issue I'm having is in the second window of code on the webpage, here is the line (it is javascript code):

DotNet.invokeMethodAsync('BlazorSample', 'ReturnArrayAsync')
      .then(data => {
        data.push(4);
          console.log(data);
      });

I am getting an error when trying to run this function on my own dot net core site: "Uncaught ReferenceError: DotNet is not defined". I've been googling as many things as I can, and I can't seem to find any reasons for having that error. I can't find any import/require type statements I could put and since I'm new to DotNet Core I'm really stuck. Does anyone know how I can get this module in the javascript, or other ways I can achieve this?

Are you creating an AspNetCore (MVC perhaps?) site, or are you creating a Blazor site? The js you quote (in fact that whole example) is all about Blazor. — Sam Axe
– Sam Axe, Commented Jun 16, 2020 at 20:36
@SamAxe When I created the project in visual studio, I believe I selected the "ASP.NET Core Web Application" template. So I probably need a different way than this tutorial since I'm not using a Blazor app I take it? — TheMooCows237
– TheMooCows237, Commented Jun 16, 2020 at 21:03

MatteKarla · Accepted Answer · 2020-06-16 20:53:15Z

5

If your only goal is to run C# code on the server called from a client side javascript, then you should look at SignalR (introduction to SignalR here)

The documentation you referenced is for Blazor, for building client apps with C#.

Are you using a sample project? (for example: Blazor WebAssembly Sample App)

If you are not running a sample project: have you included the Blazor webassembly script before your own script?

<script src="_framework/blazor.webassembly.js"></script>

edited Jun 16, 2020 at 20:53

answered Jun 16, 2020 at 20:44

MatteKarla

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1 Comment

TheMooCows237 Over a year ago

Ah, I didn't realize that was a blazor tutorial- and may have also confused blazor with razor. I am doing a ASP.NET Core visual studio template, and it looks like the SignalR you referenced will work for what I need!

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