public class PolarChartSelectionChangedEventArgs :
    EventArgs

<DxPolarChart Data=@DataSource
              PointSelectionMode="ChartSelectionMode.Multiple" 
              SelectionChanged="OnSelectionChanged">
    <DxPolarChartArgumentAxis Inverted="true" StartAngle="90" TickInterval="30"/>
    <DxPolarChartLineSeries ArgumentField="@((DataPoint i) => i.X)"
                            ValueField="@((DataPoint i) => i.Y)">
    </DxPolarChartLineSeries>
</DxPolarChart>

<p>The (@Argument; @Value) point was selected.</p>

@code {
    IEnumerable<DataPoint> DataSource = Enumerable.Empty<DataPoint>();

    object Argument, Value;

    protected override void OnInitialized () {
        DataSource = ChartContinuousDataProvider.GenerateData();
    }

    void OnSelectionChanged(PolarChartSelectionChangedEventArgs args) {
        Argument = args.Point.Argument;
        Value = args.Point.Value;
    }
}

using System;
using System.Runtime.InteropServices;

namespace BlazorDemo.Data {
// ...
    public class DataPoint {
        public double X { get; }
        public double Y { get; }

        public DataPoint(double x, double y) {
            X = x;
            Y = y;
        }
    }
}

using System.Collections.Generic;
using BlazorDemo.Data;

// ...
    public class ChartContinuousDataProvider : IChartContinuousDataProvider {
        public List<DataPoint> GenerateData() {
            return new List<DataPoint>() {
                new DataPoint(0, 0),
                new DataPoint(30, 1.7),
                new DataPoint(45, 0),
                new DataPoint(60, 1.7),
                new DataPoint(90, 0),
                new DataPoint(120, 1.7),
                new DataPoint(135, 0),
                new DataPoint(150, 1.7),
                new DataPoint(180, 0),
                new DataPoint(210, 1.7),
                new DataPoint(225, 0),
                new DataPoint(240, 1.7),
                new DataPoint(270, 0),
                new DataPoint(300, 1.7),
                new DataPoint(315, 0),
                new DataPoint(330, 1.7),
                new DataPoint(360, 0),
            };
        }
    }