WebDocumentViewerClientSideEventsBuilderBase<TBuilder, TEvents>.BeforeRender(String) Method

Specifies the JavaScript function that handles the client-side BeforeRender event.

Namespace: DevExpress.AspNetCore.Reporting.WebDocumentViewer

Assembly: DevExpress.AspNetCore.Reporting.v25.1.dll

NuGet Package: DevExpress.AspNetCore.Reporting

Declaration

C#

public TBuilder BeforeRender(
    string callback
)

VB.NET

Public Function BeforeRender(
    callback As String
) As TBuilder

Parameters

Name	Type	Description
callback	String	The name of a JavaScript function or entire JavaScript function code that runs when the BeforeRender event occurs.

Returns

Type	Description
TBuilder	WebDocumentViewerClientSideEventsBuilderBase<TBuilder, TEvents> that can be used for method chaining.

Remarks

Handle the BeforeRender event to customize the View Model before it is bound to an HTML element and/or before Knockout binding is activated.

The handler function receives two parameters. The first parameter is the object that exposes the IPreviewModel interface (or the JSReportViewer object). The second is the Document Viewer model that allows you to adjust control settings.

The following code snippet sets the zoom level to 25%, enables multi-page mode, and indicates the moment when the first page is loaded:

ASP.NET Core

<div id="loader"> <div id="loaderText"> </div> </div>
<script type="text/javascript" id="script">
    function onBeforeRender(s, e) {
        e.reportPreview.zoom = 0.25;
        e.reportPreview.showMultipagePreview = true;
        $("#loaderText").text("Waiting for the first page..");
        //Get a property that contains the document's page information.
        //Subscribe to property change.
        e.reportPreview.events.on('propertyChanged', (args) => {
            if (args.propertyName === 'pages') {
                const newValue = args.newValue;
                if (newValue.length > 0) {
                    $("#loaderText").text("");
                }
            }
        });
    }
</script>

@{
    var viewerRender = Html.DevExpress().WebDocumentViewer("DocumentViewer")
        .Height("1000px")
        .ClientSideEvents(configure => configure.BeforeRender("onBeforeRender"))
        .Bind("TestReport");
    @viewerRender.RenderHtml()
} 

Angular

  report-viewer.html

<div>
    <dx-report-viewer [reportUrl]="reportUrl" height="800px">
        <dxrv-request-options [invokeAction]="invokeAction" [host]="hostUrl">
        </dxrv-request-options>
        <dxrv-callbacks (BeforeRender)="onBeforeRender($event)">
        </dxrv-callbacks>
    </dx-report-viewer>
</div>

 

report-viewer.ts

import { Component, Inject, ViewEncapsulation, ViewChild } from '@angular/core';
import { DxReportViewerComponent } from 'devexpress-reporting-angular';


@Component({
    selector: 'report-viewer',
    encapsulation: ViewEncapsulation.None,
    templateUrl: './report-viewer.html',
    styleUrls: [
        "../../../node_modules/devextreme-dist/css/dx.light.css",
        "../../../node_modules/@devexpress/analytics-core/dist/css/dx-analytics.common.css",
        "../../../node_modules/@devexpress/analytics-core/dist/css/dx-analytics.light.css",
        "../../../node_modules/devexpress-reporting/dist/css/dx-webdocumentviewer.css"
    ]
})
export class ReportViewerComponent {
    @ViewChild(DxReportViewerComponent, { static: false }) viewer: DxReportViewerComponent;
    reportUrl: string = "TestReport";
    invokeAction: string = '/DXXRDV';

    onBeforeRender(event) {
        event.args.reportPreview.zoom = 0.25;
        event.args.reportPreview.showMultipagePreview = true;
        alert("Page load starts...");
        //Get a property that contains the document's page information. 
        var pages = event.args.reportPreview.pages;
        //Subscribe to property change.
        var pagesSubscriptionDispose = event.args.reportPreview.events.on('propertyChanged', (args) => {
            if (args.propertyName === 'pages') {
                if (args.newValue.length > 0) {
                    alert("First page is loaded.");

                pagesSubscriptionDispose();
                }
            }
        });
    }

    constructor(@Inject('BASE_URL') public hostUrl: string) { }
}

React

'use client';
import ReportViewer, { Callbacks, DxReportViewerRef, RequestOptions } from 'devexpress-reporting-react/dx-report-viewer';

function App() {
  const onBeforeRender = ({ args }): void => {
    args.reportPreview.zoom = 0.25;
    args.reportPreview.showMultipagePreview = true;
    console.log("Page load starts...");
    //Subscribe to property change. 
    args.reportPreview.events.on('propertyChanged', (e) => {
      if (e.propertyName === 'pages') {
        const newValue = e.newValue;
        if (newValue.length > 0) {
          console.log("A page is loaded. Pages.count: " + newValue.length);
        }
      }
    });
  }

  return (
    <>
      <ReportViewer reportUrl="TestExportReport">
        <RequestOptions host="http://localhost:5000/" invokeAction="/DXXRDV" />
        <Callbacks BeforeRender={onBeforeRender} />
      </ReportViewer>
    </>
  )
}

export default App

Vue

<template>
    <div ref="viewer" style="position: absolute; left: 0; right: 0; top: 0; bottom: 0" ></div>
    </template>

    <script>
    import 'devexpress-reporting/dx-webdocumentviewer';
    import { DxReportViewer } from 'devexpress-reporting/dx-webdocumentviewer';
    import * as ko from 'knockout';

    export default {
    name: "WebDocumentViewer",
    mounted() {
        const reportUrl = ko.observable("TestReport");
        const viewerRef = this.$refs.viewer;
        const requestOptions = {
            host: "https://localhost:5001/",
            invokeAction: "DXXRDV"
        };
        const callbacks = {  
            BeforeRender: function(s, e){
        e.reportPreview.zoom =0.25;
        e.reportPreview.showMultipagePreview = true;
        alert ("Page load starts...");
        //Subscribe to property change. 
        e.reportPreview.events.on('propertyChanged', (args) =>  {
        if(args.propertyName === 'pages') {
            const newValue = args.newValue;
            if (newValue.length > 0) {
                alert ("First page is loaded.");
            }
        }
        });
        }
        };
        const viewer = new DxReportViewer(viewerRef, { reportUrl, requestOptions, callbacks });
    viewer.render();
    },
    beforeUnmount() {
        ko.cleanNode(this.$refs.viewer);
    }
    };
    </script>