Toolbar.razor

@page "/toolbar/"

@using DevExpress.Blazor.Reporting
@using DevExpress.XtraReports.UI
@using BlazorCustomization.PredefinedReports
@using DevExpress.Blazor.Reporting.Models

@inject IJSRuntime JsRuntime

<div @ref="viewerComponent" style="width: 100%; height: 1000px;">
    <DxReportViewer @ref="reportViewer"
                    OnCustomizeToolbar="OnCustomizeToolbar"
                    Report="Report" />
</div>

@code {
    DxReportViewer reportViewer;
    XtraReport Report = new TableReport();
    private ElementReference viewerComponent;

    void OnCustomizeToolbar(ToolbarModel toolbarModel)
    {
        toolbarModel.AllItems.Add(new ToolbarItem()
        {
            // Use Open Iconic's icon.
            IconCssClass = "oi oi-command",
            Text = "Full Screen",
            AdaptiveText = "Full Screen",
            AdaptivePriority = 1,
            Click = async (args) =>
            {
                await JsRuntime.InvokeVoidAsync("customApi.requestFullscreen", viewerComponent);
            }
        });
    }

}