Interoperating with Javascript

The Uno boostrapper provides the ability to interoperate from and to Javascript from .NET.

Two techniques are available:

• The use of .NET 7's new generated interop features. It uses code generation to create performant, CSP-Compliant, thread-safe interop and does not make of the unsafe javascript eval.
• The use of the legacy C# Interop.Runtime.InvokeJS(...) and Javascript mono_bind_static_method(...).

Invoking C# code from Javascript

• .NET 7 JSExport
• .NET 6 mono_bind_static_method

.NET 7 introduces the [JSExportAttribute] which allows for Javascript to invoke C# static methods in a memory, threading and performance efficient way.

Important

To enable this feature, you'll need to use net7.0 or later in your project's TargetFramework, and you will need to use the Uno Bootstrapper 7.x or later.

In your C# project (named MyApp for this example), add the following class:

namespace MyNamespace;

public static partial class Exports
{
    [System.Runtime.InteropServices.JavaScript.JSExport()]
    public static string MyExportedMethod()
    {
        return $"Invoked";
    }
}

Then in your Javascript, add the following:

async function invokeCSMethod() {
    globalThis.myExports = await Module.getAssemblyExports("MyApp");
    var result = globalThis.myExports.MyNamespace.Exports.MyExportedMethod();
}

invokeCSMethod();

Invoking Javascript code from C#

• .NET 7 JSImport
• .NET 6 JSEval

Invoking JS functions from C# can be done through [JSImportAttribute].

Important

To enable this feature, you'll need to use net7.0 or later in your project's TargetFramework.

In your C# project (named MyApp for this example), add the following class:

namespace MyNamespace;

public static partial class Imports
{
    [System.Runtime.InteropServices.JavaScript.JSImport("globalThis.myJSMethod")]
    public static partial string MyJSMethod();
}

Then in your Javascript, add the following:

function myJSMethod(){
    return "myJSMethod invoked!";
}

In the C# code, call Imports.MyJSMethod(); as you would any other method.