Blazor Reporting (JavaScript-Based) - UI Customization API

February 13, 2026 · View on GitHub

This example demonstrates how to use client-side Blazor Reporting API to customize the Document Viewer and End-User Report Designer components.

Overview

The Document Viewer and Report Designer use the following objects to specify client-side event handlers:

You can define a client-side handler - a global function - in a separate JavaScript file. For example, the following function will handle the BeforeRender event to specify the Document Viewer's zoom level:

reporting_ViewerCustomization.js file

window.ReportingViewerCustomization = {
	//Change default Zoom level
	onBeforeRender: function(s, e) {
	    //-1: Page Width
	    //0: Whole Page
	    //1: 100%
	    e.reportPreview.zoom = -1;
	}
}

Reference the script file from the _Host.cshtml page.

_Host.cshtml file

<script src="~/js/reporting_ViewerCustomization.js"></script>

Assign the client-side function's name to a property in one of the objects mentioned above - DxDocumentViewerCallbacks or DxReportDesignerCallbacks.

Viewer.razor file

<DxDocumentViewer ReportUrl="SampleReport" Height="1000px" Width="100%">
	<DxDocumentViewerCallbacks BeforeRender="ReportingViewerCustomization.onBeforeRender" />
</DxDocumentViewer>

Note that you cannot use named constants in JavaScript functions. Specify strings instead.

Example: Localization

To localize Document Viewer and Report Designer UI, you need the following resources:

jQuery library. Add a reference to the _Host.cshtml page.
Translations in JSON format. You can obtain the files from the DevExpress Localization Service. Review the Localization help topic for more information.

The reporting_Localization.js file contains the onCustomizeLocalization function that loads JSON localization files. The files are located in the wwwroot\js\localization folder. Razor page markup assigns the function name to the CustomizeLocalization property in DxDocumentViewerCallbacks or DxReportDesignerCallbacks.

Note that the component's UI is built on DevExtreme widgets, so to localize the editors you should also use one of the approaches described in the following topic: DevExtreme - Localization. Specify web server's thread culture to apply culture-specific formats to numbers and dates.

Example: Anti-Forgery Tokens

To implement anti-forgery tokens that prevent CSRF attack, do the following:

Add the following code to the _Host.cshtml file:

@inject Microsoft.AspNetCore.Antiforgery.IAntiforgery antiforgery
@functions {
	string CsrfToken => antiforgery.GetAndStoreTokens(HttpContext).RequestToken;
}

Create custom controllers - WebDocumentViewerController and ReportDesignerController descendants. Apply the ValidateAntiForgeryToken and Route attributes. The Route attributes in this example use the "ViewerCsrf" or "DesignerCsrf" values, respectively.
Use the specified route values - "ViewerCsrf" and "DesignerCsrf" - to initialize the DxDocumentViewerRequestOptions.InvokeAction and DxReportDesignerRequestOptions.InvokeAction properties. Refer to the DesignerCsrf.razor and ViewerCsrf.razor files for code samples.
Handle the reporting component's BeforeRender event to add the RequestVerificationToken to the request header. Refer to the reporting_ConfigureCsrf.js file for the code sample.

Example: Document Viewer UI Customization

Related page: ViewerCustomization.razor. The reporting_ViewerCustomization.js file contains JavaScript functions that customize the Document Viewer in the following manner:

Event	Handler Implementation
CustomizeParameterEditors	Removes the time portion in the DateTime parameter editor.
BeforeRender	Sets the default zoom level to "Page Width".

Example: End-User Report Designer UI Customization

Related page: DesignerCustomization.razor.

The reporting_DesignerCustomization.js file contains JavaScript functions that customize the Report Designer in the following manner:

Event	Handler Implementation
CustomizeElements	Removes the Menu button
CustomizeMenuActions	Moves the Save and New buttons from the Menu to the Toolbar.
ReportOpened	Creates a custom report when users press the New button.
BeforeRender	Runs the Wizard when the Report Designer starts.
CustomizeWizard	Removes certain report types from the Report Wizard.

Example: Custom Controls in the Report Designer Toolbox

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