Blazor: How to pass a parameter via URL to the ViewModel (not to the page/view) - mvvm

Question

I know how to pass a parameter from the url to a blazor page like this:
#page "/myPage/{myParameter}"
#if(myParameter != null && myParameter != "")
{
<p>#myParameter</p>
}
#code{
[Parameter]
public string myParameter {get; set;};
}
If I would enter something like this in the browser: www.xyz.com/mypage/TEST
I could show 'TEST' on my page. But how can I pass a parameter directly to my injected ViewModel?
This doesn't work #page "/mypage/{ViewModel.myParameter}". The ViewModel is injected via Startup.cs and as a services.AddScoped.
I have a 'workaround':
#code {
[Parameter]
public string myParameter { get; set; }
protected override void OnInitialized() //On Page Load
{
ViewModel.myParameter = myParameter;
}
}
Is there a proper way to do this? Thx for help (still new to blazor)

Answer 1

MyParameter is extracted from the Route by the Router and passed into the page component as a Parameter in SetParametersAsync. In theory you could put in on the setter for myParameter. Don't - this is very definitely not recommended practice.
Also, Lets say you're on "/mypage/1" and you navigate to "/mypage/2", OnInitialized won't be called. You may think you're navigating between pages, but in reality, your just calling SetParametersAsync on the same component with a new value for MyParameter.
Therefore something like:
protected override void OnParametersSet()
{
if (!ViewModel.myParameter.Equals(myParameter)) ViewModel.myParameter = myParameter;
}
will ensure it is set if it changes, otherwise not (I don't know what getters/setters are on myParameter and what setting it every time on OnParametersSet precipitates!).