This change adds support for mapping DOM event handlers as tag helpers
that function in a bi-modal way.
This is a new first-class feature for DOM events, and replaces a few
workarounds like using `@onclick(...)` or `click=@{ ... }`. I haven't
removed those things yet, this is a first pass to get the new support
in, we'll remove those things when we're totally satisfied.
When used with a string like `<button onclick="foo" />` the result is
a simple HTML attribute .
But when used with an implicit expression like
`<button onclick="@Foo" />` or
`<button onclick="@(x => Clicked = true)" />` a C# function is bound to
the click event from the DOM.
This change introduces a 'tag helper' that replaces @bind with custom
code generation that accomplishes roughly the same thing.
This feature lights up by dynamically generating tag helpers that are
visible to tooling and affect the code generation based on:
- pattern recognition of component properties
- attributes that create definitions for elements
- a 'fallback' case for elements
'bind' also supports format strings (currently only for DateTime) via
a separate attribute.
This change introduces the basic framework for bind and tooling support.
We know that we'll have to do more work to define the set of default
'bind' cases for the DOM and to flesh out the conversion/formatting
infrastructure.
This change gets us far enough to replace all of the cases we currently
have tests for :) with the new features. The old @bind technique still
works for now.
Examples:
@* bind an input element to an expression *@
<input bind="@SelectedDate" format="mm/dd/yyyy" />
@functions {
public DateTime SelectedDate { get; set; }
}
@* bind an arbitrary expression to an arbitrary set of attributes *@
<div bind-myvalue-myevent="@SomeExpression">...</div>
@* write a component that supports bind *@
@* in Counter.cshtml *@
<div>...html omitted for brevity...</div>
@functions {
public int Value { get; set; } = 1;
public Action<int> ValueChanged { get; set; }
}
@* in another file *@
<Counter bind-Value="@CurrentValue" />
@functions {
public int CurrentValue { get; set; }
}
This builds upon existing support for UIEventHandler-typed component
properties and applies the same principle to any delegate type.
We try to help by generating the LSH of the lambda `=>` allowing you to
write `OnClick="Foo()"` rather than `OnClick="(e) => Foo()"`. You can of
course use @ as an escape.
The only rough edge here is that if the parameter names aren't memorable
for the delgate type, it's not super helpful.
Implements Component code generation and tooling support end to end
udditionally adds some default `@addTagHelper` directives to make
programming in Blazor a little nicer.
Components are discovered as Tag Helpers using Razor's extensibility
during the build/IDE process. This drives the code generation during
build and lights up a bunch of editor features.
Add
Ryan Nowak
Ryan Nowak
flash2048