Workbook.ExportToHtmlAsync(Stream, Worksheet, CancellationToken, IProgress<Int32>) Method

Asynchronously exports the specified worksheet to a stream in HTML format. Allows you to implement progress notifications and cancel the operation.

You need a license for the DevExpress Office File API Subscription or DevExpress Universal Subscription to use this method in production code.

Namespace: DevExpress.Spreadsheet

Assembly: DevExpress.Docs.v25.1.dll

NuGet Package: DevExpress.Document.Processor

Declaration

C#

public Task ExportToHtmlAsync(
    Stream stream,
    Worksheet sheet,
    CancellationToken cancellationToken,
    IProgress<int> progress
)

VB.NET

Public Function ExportToHtmlAsync(
    stream As Stream,
    sheet As Worksheet,
    cancellationToken As CancellationToken,
    progress As IProgress(Of Integer)
) As Task

Parameters

Name	Type	Description
stream	Stream	Specifies the output stream.
sheet	Worksheet	A worksheet to save as HTML.
cancellationToken	CancellationToken	A cancellation token that indicates whether to cancel the operation.
progress	IProgress<Int32>	An object used to report the task progress in percentage. Use a Progress<T> class instance to report progress.

Returns

Type	Description
Task	An object that defines the asynchronous export operation.

Remarks

Important

Take into account the following when you call this method:

• The events fired by this method call may occur in a different thread than the target operation.

• The operation is not thread safe (the document should not be accessed simultaneously by different threads). Wait until the operation is completed before you continue to work with the document (for example, use the await operator).

Example: Report Progress of Workbook Operations

The following example asynchronously loads a workbook and exports the first worksheet to HTML. The console window displays the progress of each operation. If the load or export operation takes longer than 30 seconds, it is canceled.

C#

using System;
using System.IO;
using System.Threading;
using System.Threading.Tasks;
using DevExpress.Spreadsheet;
// ...

static async Task Main(string[] args) {
    var cancellationSource = new CancellationTokenSource(TimeSpan.FromSeconds(30));
    var cancellationToken = cancellationSource.Token;
    try {
        using (Workbook workbook = new Workbook()) {
            Console.WriteLine("Loading a document...");
            await workbook.LoadDocumentAsync("Document.xlsx",
                cancellationToken,
                new Progress<int>((progress) => Console.WriteLine($"{progress}%")));
            Worksheet worksheet = workbook.Worksheets[0];
            Console.WriteLine("Exporting to HTML...");
            using (FileStream htmlStream = new FileStream("HtmlDocument.html", FileMode.Create))
            {
                await workbook.ExportToHtmlAsync(htmlStream, worksheet,
                cancellationToken,
                new Progress<int>((progress) => Console.WriteLine($"{progress}%")));
            }
            Console.WriteLine("Done!");
        }
    }
    catch (OperationCanceledException) {
        Console.WriteLine("Cancelled by timeout.");
    }
    finally {
        cancellationSource.Dispose();
    }
}

VB.NET

Imports System
Imports System.IO
Imports System.Threading
Imports System.Threading.Tasks
Imports DevExpress.Spreadsheet

Module Example
    Sub Main()
        MainAsync().Wait()
    End Sub
    Async Function MainAsync() As Task
        Dim cancellationSource As New CancellationTokenSource(TimeSpan.FromSeconds(30))
        Dim cancellationToken As CancellationToken = cancellationSource.Token
        Try
            Using workbook As New Workbook()
                Console.WriteLine("Loading a document...")
                Await workbook.LoadDocumentAsync("Document.xlsx", cancellationToken,
                    New Progress(Of Integer)(Sub(progress) Console.WriteLine($"{progress}%")))
                Dim worksheet As Worksheet = workbook.Worksheets(0)
                Console.WriteLine("Exporting to HTML...")
                Using htmlStream As New FileStream("HtmlDocument.html", FileMode.Create)
                    Await workbook.ExportToHtmlAsync(htmlStream, worksheet, 
                        cancellationToken, 
                        New Progress(Of Integer)(Sub(progress) Console.WriteLine($"{progress}%")))
                End Using
                Console.WriteLine("Done!")
            End Using
        Catch e1 As OperationCanceledException
            Console.WriteLine("Cancelled by timeout.")
            Console.ReadLine()
        Finally
            cancellationSource.Dispose()
        End Try
    End Function
End Module

Calculate Formulas Before Export

The default calculation mode for a Workbook is Manual. This mode implies that the Spreadsheet does not recalculate formulas before it generates an HTML file. Call the Workbook.Calculate or Workbook.CalculateFull method to calculate all formulas in the workbook before you export it to HTML.