Blazor - Get object set by parent-CodePudding

I've the following piece of code:

@page "somePage"

<TeamsApplication RequireAuthentication="true">
    <ApplicationTemplate Context="context">
        Some HTML...
        @*context works here*@
    </ApplicationTemplate>
</TeamsApplication>

@code{
  //context doesnt work here
}

Inside ApplicationTemplate tag I can access context object instance, but can't do it in code section. Is there a way I could access that instance and its values?

CodePudding user response：

Properties normally flow down, not up. So the Context property won't work like that. The simplest solution I could think of is an EventCallback, so that the ApplicationTemplate sends a message to the parent that the Context is available

ApplicationTemplate.razor


    [Parameter] public EventCallback<Context> ContextChanged {  get;  set; }

    /// <summary>
    /// Context was set from somewhere
    /// </summary>
    async Task ContextSet(Context newValue)
    {
        // notify anyone listening to ContextChanged
        await ContextChanged.InvokeAsync(newValue);
    }

Then in your page logic you listen to this event callback:


<TeamsApplication>
    <ApplicationTemplate ContextChanged=HandleContextChanged>
        @* todo *@
    </ApplicationTemplate>

</TeamsApplication>

@code
{
    /// <summary>
    /// Handle event from ApplicationTemplate
    /// </summary>
    /// <param name="context"></param>
    /// <returns></returns>
    async Task HandleContextChanged(Context context)
    {
        // context is now available
        
    }

}

CodePudding user response：

You can create a function that accepts a parameter of the same type of your context Type and so you have access within that function, but the question is: what you need that context for?

If you need to create a custom component that need to have access to that context, pass it to another child component, then create a [Parameter] of type RenderFragment and so you can deal with it as you want.

You can even create a local function that renders a RenderFragment but the Razor syntax for that kind of stuff is quite akward and a bit bugged

For example I have a method like this

public RenderFragment DefaultActionTemplate(PanelAction action) =>@:@{
      if (action.IsToggle) {
         <div>Toggle</div>
      }
      else {
         <div>Button</div>
      }
   }
   ;

You can do the same and use your context Type instead of my PanelAction, the concept is the same

As I told you tho, the syntax is awkward and the semicolon you see at the end, need to be on a new line and can't be next the closing curly braket see this issue: https://github.com/dotnet/aspnetcore/issues/11612