WebDocumentViewerBuilder.Nonce(String) Method

Specifies the nonce value.

Namespace: DevExpress.AspNetCore.Reporting.WebDocumentViewer

Assembly: DevExpress.AspNetCore.Reporting.v23.2.dll

NuGet Package: DevExpress.AspNetCore.Reporting

Declaration

C#

public WebDocumentViewerBuilder Nonce(
    string nonce
)

VB.NET

Public Function Nonce(
    nonce As String
) As WebDocumentViewerBuilder

Parameters

Name	Type	Description
nonce	String	A String that specifies the nonce value.

Returns

Type	Description
WebDocumentViewerBuilder	A WebDocumentViewerBuilder that can be used to further configure the Document Viewer.

Example

This example demonstrates how to implement a nonce-based Content Security Policy (CSP) for an ASP.NET Core Application through an HTTP response header:

View Example

In the HomeController.cs file, generate the nonce value. The RandomNumberGenerator class is used to generate cryptographically strong random values. Add an HTTP header with the Content Security Policy with nonce for the script-src directive.

The following code snippet shows how to add a nonce-based CSP for the Document Viewer component:

using DevExpress.AspNetCore.Reporting.WebDocumentViewer;
using DevExpress.XtraReports.Web.WebDocumentViewer;
using Microsoft.AspNetCore.Mvc;
using System;
using System.Security.Cryptography;
using System.Threading.Tasks;
//...
public async Task<IActionResult> Viewer(
    [FromServices] IWebDocumentViewerClientSideModelGenerator clientSideModelGenerator,
    [FromQuery] string reportName) {
    var nonceBytes = new byte[32];
    using var generator = RandomNumberGenerator.Create();
    generator.GetBytes(nonceBytes);
    var nonce = Convert.ToBase64String(nonceBytes);
    HttpContext.Response.Headers.Add("Content-Security-Policy",
                string.Format("script-src 'self' 'nonce-{0}';", nonce) +
                "img-src data: https: http:;" +
                "style-src 'self';" +
                "connect-src 'self';" +
                "worker-src 'self' blob:;" +
                "frame-src 'self' blob:;"
            );
    var reportToOpen = string.IsNullOrEmpty(reportName) ? "TestReport" : reportName;
    var model = new Models.ViewerModel {
        ViewerModelToBind = await clientSideModelGenerator.GetModelAsync(reportToOpen, WebDocumentViewerController.DefaultUri),
        Nonce = nonce
    };
    return View(model);
}
//...

The new nonce value is generated each time the page loads.

On the page, pass the nonce value to the Nonce method:

@*...*@
@{
    var viewerRender = Html.DevExpress().WebDocumentViewer("DocumentViewer")
        .Height(null)
        .Width(null)
        .Nonce(Model.Nonce)
        .CssClassName("my-reporting-component")
        .Bind(Model.ViewerModelToBind);
    @viewerRender.RenderHtml()
}

Note

Set the Height and Width properties to null for the application to work properly. You can specify the required height and width in a CSS class.