Solution needed for Field initializer cannot reference the non-static field method or property in Blazor

Question

I'm working on a Blazor project, but my problem is C#. I do understand the problem, but I just can not solve it in the Blazor context.

In my razor page I use a blazorise linechart that takes dates for the x-axis. That works perfectly well if I use non-dynamic dates. The

<LineChart @ref="lineChart" TItem="double" OptionsObject="@options"/>

However, to determine the dates (so the x-axis labels) dynamically, I need the following code behind:

public partial class ChartComponent : ComponentBase
    {    
        [Parameter]
        public List<Observation> Observations { get; set; }     //an Observation has a field with a Date in it. 

        Object options = new            
        {
            Scales = new
            {
                XAxes = new[]
                {
                    new
                    {
                        labels =   new[]{GetDateTimeLabels()}   //this gets me the error, if I use new[]{DateTime.Now,...,DateTime.Now+n} it works just fine.
                    }
                }
            }
        };


public DateTime[] GetDateTimeLabels()
        {
            DateTime[] dateLabels = VACRAObservations.Select(x => x.Date).ToArray();
            return dateLabels;
        }

This gets me an error "a field initializer cannot reference the non-static field method or property", which I understand, because the compiler does not know if GetLabels() is ready before Object options is initialized.

I cannot go around the [Parameter], I need it to get the list of Observations into the razor page.

I tried to put it all in the constructor, but the constructor is initialized before the parameter is taken in.

I tried to do it with statics, but a static class can not derive from Componentbase class.

I'm at a loss what to do. Please let me know if you need more information.

Answer 1

The easiest fix is to make it a property. When you only need it once, add a > :

 Object options => new   {  ...  };         

and when you need to guard against evaluating it too often:

 Object _options = null;
 Object options => _options ?? (_options = new            
    {
        ... // as before
    });