public class DxMarginSettings :
    DxSettingsComponent<MarginSettingsModel>

<DxSparkline Data="@DataSource"
             CssClass="myCssClass"
             Type="SparklineType.Bar"
             ArgumentFieldName="Month"
             ValueFieldName="VisitorCount"
             Height="50px"
             Width="200px">
    <DxMarginSettings Top="10" Right="20" Bottom="10" Left="20"/>
</DxSparkline>

@code {
    IEnumerable<SparklineDataPoint> DataSource = Enumerable.Empty<SparklineDataPoint>();
    protected override void OnInitialized() {
        DataSource = GenerateData();
    }
}

public List<SparklineDataPoint> GenerateData() {
    return new List<SparklineDataPoint>() {
            new SparklineDataPoint( 01, 2132),
            new SparklineDataPoint( 02, 2103),
            new SparklineDataPoint( 03, 2460),
            new SparklineDataPoint( 04, 2152),
            new SparklineDataPoint( 05, 2062),
            new SparklineDataPoint( 06, 1934),
            new SparklineDataPoint( 07, 2112),
            new SparklineDataPoint( 08, 1967),
            new SparklineDataPoint( 09, 2009),
            new SparklineDataPoint( 10, 2087),
            new SparklineDataPoint( 11, 2112),
            new SparklineDataPoint( 12, 2038),
        };
}
public class SparklineDataPoint {
    public int Month { get; set; }
    public int? VisitorCount { get; set; }
    public SparklineDataPoint(int month, int? visitorCount) {
        Month = month;
        VisitorCount = visitorCount;
    }
}

.myCssClass .dxbl-widget-container {
    border: 1px solid black;
}