Writing java script for Csharp's Blazor
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1. JavaScript interop in Blazor allows .NET methods to invoke JavaScript functions and JavaScript functions to invoke .NET methods. 2. There are several scenarios for JavaScript interop including one-way calls from .NET to JavaScript, round-trip calls between .NET and JavaScript, and using callbacks. 3. The developer must consider lifecycle awareness when using JavaScript interop to ensure JavaScript is initialized properly, such as in the OnAfterRenderAsync method.
![Scenarios: Round Trip (JS >< C#)
[JSInvokable] Attribute
Invoke C# Static Method from JS
JS C# RaiseEvent
Value
[JSInvokable]
[JSInvokable]
public static Task<int[]> ReturnArrayAsync()
Task.FromResult(new int[] { 1, 2, 3 });
returnArrayAsyncJs: function () {
DotNet.invokeMethodAsync(‘namespace', 'ReturnArrayAsync')
.then(data => {
data.push(4);
console.log(data);
});
},
C#
JS](https://image.slidesharecdn.com/writingjavascriptforcsharpsblazor-200820183618/85/Writing-java-script-for-Csharp-s-Blazor-12-320.jpg)
![Scenarios: Round-Trip Callback
public class GeoLocation
{
public async ValueTask GetCurrentPosition(...) =>
await js.InvokeVoidAsync
("blazorGeolocation.getCurrentPosition",
DotNetObjectReference.Create(this), options);
[JSInvokable]
public void RaiseOnGetPosition(Position p) =>
[JSInvokable]
public void RaiseOnGetPositionError(Error err) =>
window.blazorGeolocation = {
getCurrentPosition: function (geolocationRef, options) {
navigator.geolocation
.getCurrentPosition(onSuccess, onError, options);
},
function onSuccess(result) {
return geolocationRef
.invokeMethodAsync('RaiseOnGetPosition’,
blazorGeolocation.toSerializeable(result));
};
function onError(er) {
return geolocationRef
.invokeMethodAsync('RaiseOnGetPositionError’,
er.code);
};
};
JSC#](https://image.slidesharecdn.com/writingjavascriptforcsharpsblazor-200820183618/85/Writing-java-script-for-Csharp-s-Blazor-14-320.jpg)
![Scenarios: Round-Trip Callback
public class GeoLocation
{
public async ValueTask GetCurrentPosition(...) =>
await js.InvokeVoidAsync
("blazorGeolocation.getCurrentPosition",
DotNetObjectReference.Create(this), options);
[JSInvokable]
public void RaiseOnGetPosition(Position p) =>
[JSInvokable]
public void RaiseOnGetPositionError(Error err) =>
window.blazorGeolocation = {
getCurrentPosition: function (geolocationRef, options) {
navigator.geolocation
.getCurrentPosition(onSuccess, onError, options);
},
function onSuccess(result) {
return geolocationRef
.invokeMethodAsync('RaiseOnGetPosition’,
blazorGeolocation.toSerializeable(result));
};
function onError(er) {
return geolocationRef
.invokeMethodAsync('RaiseOnGetPositionError’,
er.code);
};
};
JSC#](https://image.slidesharecdn.com/writingjavascriptforcsharpsblazor-200820183618/85/Writing-java-script-for-Csharp-s-Blazor-15-320.jpg)
![Scenarios: Round-Trip Callback
public class GeoLocation
{
public async ValueTask GetCurrentPosition(...) =>
await js.InvokeVoidAsync
("blazorGeolocation.getCurrentPosition",
DotNetObjectReference.Create(this), options);
[JSInvokable]
public void RaiseOnGetPosition(Position p) =>
[JSInvokable]
public void RaiseOnGetPositionError(Error err) =>
window.blazorGeolocation = {
getCurrentPosition: function (geolocationRef, options) {
navigator.geolocation
.getCurrentPosition(onSuccess, onError, options);
},
function onSuccess(result) {
return geolocationRef
.invokeMethodAsync('RaiseOnGetPosition’,
blazorGeolocation.toSerializeable(result));
};
function onError(er) {
return geolocationRef
.invokeMethodAsync('RaiseOnGetPositionError’,
er.code);
};
};
JSC#](https://image.slidesharecdn.com/writingjavascriptforcsharpsblazor-200820183618/85/Writing-java-script-for-Csharp-s-Blazor-16-320.jpg)
![Scenarios: Round-Trip Callback
public class GeoLocation
{
public async ValueTask GetCurrentPosition(...) =>
await js.InvokeVoidAsync
("blazorGeolocation.getCurrentPosition",
DotNetObjectReference.Create(this), options);
[JSInvokable]
public void RaiseOnGetPosition(Position p) =>
[JSInvokable]
public void RaiseOnGetPositionError(Error err) =>
window.blazorGeolocation = {
getCurrentPosition: function (geolocationRef, options) {
navigator.geolocation
.getCurrentPosition(onSuccess, onError, options);
},
function onSuccess(result) {
return geolocationRef
.invokeMethodAsync('RaiseOnGetPosition’,
blazorGeolocation.toSerializeable(result));
};
function onError(er) {
return geolocationRef
.invokeMethodAsync('RaiseOnGetPositionError’,
er.code);
};
};
JSC#](https://image.slidesharecdn.com/writingjavascriptforcsharpsblazor-200820183618/85/Writing-java-script-for-Csharp-s-Blazor-17-320.jpg)
![Pub-Sub: Developer Experience
JS C#
DOM EventA
DOM EventB
Channel
Component (A)
Component
(AB)
Component (B)
Component
(AB)
<MediaQueryList>
<MediaQuery>
<MediaQuery>
<MediaQuery>
<MediaQuery>
mediaQueryLists: MediaQueryListItem[]
MediaQueryListItem {
id: number | string;
dotnetCallback: (ev: MediaQueryListEvent)
mediaQueries: MediaQueryList[];
}](https://image.slidesharecdn.com/writingjavascriptforcsharpsblazor-200820183618/85/Writing-java-script-for-Csharp-s-Blazor-22-320.jpg)
![Typescript
DotNetObjectReference type is number | string (int | guid)
Remove .json files from NuGet Packages
{
"compilerOptions": {
"outDir": "./wwwroot",
"target": "ES6",
"moduleResolution": "node",
"lib": [ "ES2016", "DOM"]
},
"exclude": [
"node_modules",
"wwwroot",
"**/*.test.ts"
]
}
tsconfig.json](https://image.slidesharecdn.com/writingjavascriptforcsharpsblazor-200820183618/85/Writing-java-script-for-Csharp-s-Blazor-25-320.jpg)
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Writing java script for Csharp's Blazor
- 2. Ed Charbeneau Author: Sr. Developer Advocate Progress Software, Telerik UI for Blazor “Blazor: A Beginner's Guide” (free) Тwitter: @EdCharbeneau Тwitch: Twitch.tv/EdCharbeneau
- 3. Why do we need it? Blazor is really, really, new! C# Doesn’t have a full API surface for the Browser’s Web APIs
- 5. Why do don’t we need it? LocalStorage ◦ dotnet add package Blazored.LocalStorage MediaQueries ◦ dotnet add package BlazorPro.BlazorSize File Uploads ◦ dotnet add package Telerik.UI.for.Blazor • Commercial library .NET 5 ◦ SEO support, <Head>
- 6. What’s the JavaScript Interop A Blazor app can invoke JavaScript functions from .NET methods and .NET methods from JavaScript functions.
- 7. How do we do it? C# API DotNetObjectReference<T> ◦ Value (T instance) ◦ Dispose() IJSRuntime ◦ .InvokeAsync<T>(fname, p) ◦ .InvokeVoidAsync(fname, p) JAVASCRIPT API DotNetObjectReference ◦ number | string (guid) ◦ invokeMethodAsync(fname, p) ◦ dispose Parameters & Values must be JSON serializeable
- 8. How do we do it? CONVENTION Use namespaces window.namespace.function window.myFoo = { doFoo: function() {} } UNLESS The function already exists on the window object. window.alert Parameters & Values must be JSON serializeable
- 10. Scenarios: One Way Invoke JavaScript from C# Fire and forget No return value private readonly IJSRuntime jsRuntime; private async ValueTask Cancel() => await jsRuntime.InvokeVoidAsync($“namespace.functionName“, parameters); C# JS window.alert Void C# window.namespace = { function: functionName() } JS
- 11. Scenarios: Round Trip (C# > JS) Invoke JavaScript from C# Return value C# JS invokeMethod Value string name = await js.InvokeAsync<string>("prompt", "What is your name?"); Result = $"Your name is: {name}"; C#
- 12. Scenarios: Round Trip (JS >< C#) [JSInvokable] Attribute Invoke C# Static Method from JS JS C# RaiseEvent Value [JSInvokable] [JSInvokable] public static Task<int[]> ReturnArrayAsync() Task.FromResult(new int[] { 1, 2, 3 }); returnArrayAsyncJs: function () { DotNet.invokeMethodAsync(‘namespace', 'ReturnArrayAsync') .then(data => { data.push(4); console.log(data); }); }, C# JS
- 13. Scenarios: Round-Trip Callback Invoke JavaScript from .NET Invoke C# Instance Method from JS DotNetObjectReference Dispose, dispose, dispose C# JS Function.callbac k Value R RInstance.method
- 14. Scenarios: Round-Trip Callback public class GeoLocation { public async ValueTask GetCurrentPosition(...) => await js.InvokeVoidAsync ("blazorGeolocation.getCurrentPosition", DotNetObjectReference.Create(this), options); [JSInvokable] public void RaiseOnGetPosition(Position p) => [JSInvokable] public void RaiseOnGetPositionError(Error err) => window.blazorGeolocation = { getCurrentPosition: function (geolocationRef, options) { navigator.geolocation .getCurrentPosition(onSuccess, onError, options); }, function onSuccess(result) { return geolocationRef .invokeMethodAsync('RaiseOnGetPosition’, blazorGeolocation.toSerializeable(result)); }; function onError(er) { return geolocationRef .invokeMethodAsync('RaiseOnGetPositionError’, er.code); }; }; JSC#
- 15. Scenarios: Round-Trip Callback public class GeoLocation { public async ValueTask GetCurrentPosition(...) => await js.InvokeVoidAsync ("blazorGeolocation.getCurrentPosition", DotNetObjectReference.Create(this), options); [JSInvokable] public void RaiseOnGetPosition(Position p) => [JSInvokable] public void RaiseOnGetPositionError(Error err) => window.blazorGeolocation = { getCurrentPosition: function (geolocationRef, options) { navigator.geolocation .getCurrentPosition(onSuccess, onError, options); }, function onSuccess(result) { return geolocationRef .invokeMethodAsync('RaiseOnGetPosition’, blazorGeolocation.toSerializeable(result)); }; function onError(er) { return geolocationRef .invokeMethodAsync('RaiseOnGetPositionError’, er.code); }; }; JSC#
- 16. Scenarios: Round-Trip Callback public class GeoLocation { public async ValueTask GetCurrentPosition(...) => await js.InvokeVoidAsync ("blazorGeolocation.getCurrentPosition", DotNetObjectReference.Create(this), options); [JSInvokable] public void RaiseOnGetPosition(Position p) => [JSInvokable] public void RaiseOnGetPositionError(Error err) => window.blazorGeolocation = { getCurrentPosition: function (geolocationRef, options) { navigator.geolocation .getCurrentPosition(onSuccess, onError, options); }, function onSuccess(result) { return geolocationRef .invokeMethodAsync('RaiseOnGetPosition’, blazorGeolocation.toSerializeable(result)); }; function onError(er) { return geolocationRef .invokeMethodAsync('RaiseOnGetPositionError’, er.code); }; }; JSC#
- 17. Scenarios: Round-Trip Callback public class GeoLocation { public async ValueTask GetCurrentPosition(...) => await js.InvokeVoidAsync ("blazorGeolocation.getCurrentPosition", DotNetObjectReference.Create(this), options); [JSInvokable] public void RaiseOnGetPosition(Position p) => [JSInvokable] public void RaiseOnGetPositionError(Error err) => window.blazorGeolocation = { getCurrentPosition: function (geolocationRef, options) { navigator.geolocation .getCurrentPosition(onSuccess, onError, options); }, function onSuccess(result) { return geolocationRef .invokeMethodAsync('RaiseOnGetPosition’, blazorGeolocation.toSerializeable(result)); }; function onError(er) { return geolocationRef .invokeMethodAsync('RaiseOnGetPositionError’, er.code); }; }; JSC#
- 18. Pub-Sub JS C# DOM EventA DOM EventB Channel Component (A) Component (AB) Component (B) Component (AB)
- 19. Pub-Sub: Init JS C# Channel Component (A) .addEventListener DOM EventA
- 20. Pub-Sub: De-dupe JS C# Channel Component (A) .addEventListener DOM EventA DOM EventB Component (AB) DOM EventA
- 21. Pub-Sub: Dispose JS C# DOM EventA DOM EventB Channel Component (A) Component (AB) Component (B) Component (AB) .removeEventListener .Dispose
- 22. Pub-Sub: Developer Experience JS C# DOM EventA DOM EventB Channel Component (A) Component (AB) Component (B) Component (AB) <MediaQueryList> <MediaQuery> <MediaQuery> <MediaQuery> <MediaQuery> mediaQueryLists: MediaQueryListItem[] MediaQueryListItem { id: number | string; dotnetCallback: (ev: MediaQueryListEvent) mediaQueries: MediaQueryList[]; }
- 23. Component Lifecycle Awareness SetParametersAsync() OnInitializedAsync() OnParametersSetAsync() OnAfterRenderAsync(bool firstRender) ShouldRender() Avoid JavaScript interop during Initialization. Because Blazor can utilize Server rendering, JavaScript may not be available. Use OnAfterRenderAsync for initializing JavaScript.
- 25. Typescript DotNetObjectReference type is number | string (int | guid) Remove .json files from NuGet Packages { "compilerOptions": { "outDir": "./wwwroot", "target": "ES6", "moduleResolution": "node", "lib": [ "ES2016", "DOM"] }, "exclude": [ "node_modules", "wwwroot", "**/*.test.ts" ] } tsconfig.json
- 26. _content/Namespace/resource.* Razor Class Library Assets go in wwwroot wwwroot becomes => _content/Namespace/* Do provide minified and standard formats Example <script src="_content/BlazorPro.BlazorSize/blazorSize.min.js"></script>
- 27. QUESTIONS Resources 1. EdCharbeneau.com • Free Ebook & examples • GitHub • Twitter • Twitch 2. Blogs.Telerik.com