OnParametersSetAsync ?

[chanan]

Hi,

In issue aspnet/Blazor#1252 @danroth27 mentioned that OnParametersSetAsync will be added, but it doesnt seem to be there in the V0.7.0. Is it going to be added soon?

Thanks,
Chanan

[michaelvolz]

@chanan Hi, I am using it. It works as expected. Blazor 0.7

[chanan]

@michaelvolz What method signature are you using or what interface are you overriding?

I only see IComponent.SetParameters(ParameterCollection parameters)

[michaelvolz]

@chanan I simply inherit from Blazorcomponent. The IComponent interface doesn't have the methods declared.

using Microsoft.AspNetCore.Blazor.RenderTree;
using System;
using System.Threading.Tasks;

namespace Microsoft.AspNetCore.Blazor.Components
{
  /// <summary>
  /// Optional base class for Blazor components. Alternatively, Blazor components may
  /// implement <see cref="T:Microsoft.AspNetCore.Blazor.Components.IComponent" /> directly.
  /// </summary>
  public abstract class BlazorComponent : IComponent, IHandleEvent, IHandleAfterRender
  {
    /// <summary>
    /// Constructs an instance of <see cref="T:Microsoft.AspNetCore.Blazor.Components.BlazorComponent" />.
    /// </summary>
    public BlazorComponent()
    {
      this._renderFragment = new RenderFragment(this.BuildRenderTree);
    }

[...]

    /// <summary>
    /// Method invoked when the component is ready to start, having received its
    /// initial parameters from its parent in the render tree.
    /// </summary>
    protected virtual void OnInit()
    {
    }

    /// <summary>
    /// Method invoked when the component is ready to start, having received its
    /// initial parameters from its parent in the render tree.
    /// 
    /// Override this method if you will perform an asynchronous operation and
    /// want the component to refresh when that operation is completed.
    /// </summary>
    /// <returns>A <see cref="T:System.Threading.Tasks.Task" /> representing any asynchronous operation.</returns>
    protected virtual Task OnInitAsync()
    {
      return Task.CompletedTask;
    }

    /// <summary>
    /// Method invoked when the component has received parameters from its parent in
    /// the render tree, and the incoming values have been assigned to properties.
    /// </summary>
    protected virtual void OnParametersSet()
    {
    }

    /// <summary>
    /// Method invoked when the component has received parameters from its parent in
    /// the render tree, and the incoming values have been assigned to properties.
    /// </summary>
    /// <returns>A <see cref="T:System.Threading.Tasks.Task" /> representing any asynchronous operation.</returns>
    protected virtual Task OnParametersSetAsync()
    {
      return Task.CompletedTask;
    }

    /// <summary>
    /// Method invoked after each time the component has been rendered.
    /// </summary>
    protected virtual void OnAfterRender()
    {
    }

    /// <summary>
    /// Method invoked after each time the component has been rendered. Note that the component does
    /// not automatically re-render after the completion of any returned <see cref="T:System.Threading.Tasks.Task" />, because
    /// that would cause an infinite render loop.
    /// </summary>
    /// <returns>A <see cref="T:System.Threading.Tasks.Task" /> representing any asynchronous operation.</returns>
    protected virtual Task OnAfterRenderAsync()
    {
      return Task.CompletedTask;
    }

    /// <summary>
    /// Method invoked to apply initial or updated parameters to the component.
    /// </summary>
    /// <param name="parameters">The parameters to apply.</param>
    public virtual void SetParameters(ParameterCollection parameters)
    {
      parameters.AssignToProperties((object) this);
      if (!this._hasCalledInit)
      {
        this._hasCalledInit = true;
        this.OnInit();
        Task task = this.OnInitAsync();
        if (task != null && task.Status != TaskStatus.RanToCompletion)
          task.ContinueWith(new Action<Task>(this.ContinueAfterLifecycleTask));
      }
      this.OnParametersSet();
      Task task1 = this.OnParametersSetAsync();
      if (task1 != null && task1.Status != TaskStatus.RanToCompletion)
        task1.ContinueWith(new Action<Task>(this.ContinueAfterLifecycleTask));
      this.StateHasChanged();
    }

[...]

  }
}

[chanan]

Thanks @michaelvolz I will try it out!

[chanan]

Sadly, while it might work (not sure yet), doesn't looks like dynamic attributes will work anymore.

@SteveSandersonMS Can you suggest a solution here?

If you recall, I took your code from when you started on the bootstrap components and I am using it here: https://github.com/chanan/Blazorous/blob/master/src/Blazorous/Dynamic.cs - but when I run it as inherits from BalzorComponent so that I can use OnParametersSetAsync (which doesnt seem to exist in an interface) I no longer respects attributes as being dynamic and I get the error that I need to have the [Parameter] attribute (Or maybe I would get that error either way, not sure).

[chanan]

Robin Sue in the glitter.im room pointed me to https://github.com/aspnet/Blazor/issues/1659#issuecomment-437944981 which fixes my issues.