XtraReport.ExportToHtmlAsync(Stream, HtmlExportOptions, CancellationToken) Method

Asynchronously exports a report to the specified stream in HTML format.

Namespace: DevExpress.XtraReports.UI

Assembly: DevExpress.XtraReports.v24.1.dll

NuGet Package: DevExpress.Reporting.Core

Declaration

C#

public Task ExportToHtmlAsync(
    Stream stream,
    HtmlExportOptions options = null,
    CancellationToken token = default(CancellationToken)
)

VB.NET

Public Function ExportToHtmlAsync(
    stream As Stream,
    options As HtmlExportOptions = Nothing,
    token As CancellationToken = Nothing
) As Task

Parameters

Name	Type	Description
stream	Stream	A Stream for output data.

Optional Parameters

Name	Type	Default	Description
options	HtmlExportOptions	null	The HTML export options. You can omit this parameter to use the current report export options.
token	CancellationToken	null	A cancellation token that the task observes.

Returns

Type	Description
Task	A task that exports the report.

Remarks

This method is equivalent to the ExportToHtml(Stream, HtmlExportOptions) method but does not lock other actions performed concurrently. For instance, the user interface remains operational while the application exports a report.

Call ExportToHtmlAsync from an async method. Prefix the call with the await operator, as shown in the code sample below.

The optional CancellationToken parameter provides a way to send the cancellation signal to the task. The task monitors the token and stops when it receives the signal. Create a CancellationTokenSource class instance and pass its Token property to the ExportToHtmlAsync method call. Call the CancellationTokenSource.Cancel method to stop the task.

Example

The code sample below exports a report to HTML asynchronously. A CancellationTokenSource class instance is used to allow users to interrupt the report export if it takes too long.

C#

using DevExpress.XtraReports.UI;
using System;
using System.Threading;
// ...
using System.IO;
// ...
// Use cancellationTokenSource to allow users to stop the document creation process.
CancellationTokenSource cancellationTokenSource = new CancellationTokenSource();
// ...
// The cancelButton_Click event handler uses cancellationTokenSource to stop the document creation process.
private void cancelButton_Click(object sender, EventArgs e)
{
    cancellationTokenSource.Cancel();
}
// ...
async public void ExportReportToHtmlStreamAsync()
{
    // Create a simple report.
    XtraReport report = new XtraReport()
    {
        Name = "SimpleReport",
        Bands = {
            new DetailBand() {
                Controls = {
                    new XRLabel() {
                        Text = "Simple Report"
                    }
                }
            }
        }
    };
    // Create the export file in the user's Downloads folder.
    FileStream stream = File.Open(
        Environment.GetFolderPath(Environment.SpecialFolder.UserProfile) + @"\Downloads\" + report.Name + ".html",
        FileMode.Create);
    // Export the report to the created file.
    await report.ExportToHtmlAsync(
        stream,
        null,
        cancellationTokenSource.Token);
}

VB.NET

Imports DevExpress.XtraReports.UI
Imports System.Threading
' ...
Imports System.IO
' ...
' Use cancellationTokenSource to allow users to stop the document creation process.
Private cancellationTokenSource As New CancellationTokenSource()
' ...
' The cancelButton_Click event handler uses cancellationTokenSource to stop the document creation process.
Private Sub cancelButton_Click(ByVal sender As Object, ByVal e As EventArgs)
    cancellationTokenSource.Cancel()
End Sub
' ...
Public Async Sub ExportReportToHtmlStreamAsync()
    ' Create a simple report.
    Dim report = New XtraReport() With {.Name = "SimpleReport"}
    Dim band = New DetailBand()
    Dim control = New XRLabel() With {.Text = "Simple Report"}
    band.Controls.Add(control)
    report.Bands.Add(band)
    ' Create the export file in the user's Downloads folder.
    Dim stream As FileStream = File.Open(Environment.GetFolderPath(Environment.SpecialFolder.UserProfile) _
                                         & "\Downloads\" & report.Name & ".html", FileMode.Create)
    ' Export the report to the created file.
    Await report.ExportToHtmlAsync(stream, Nothing, cancellationTokenSource.Token)
End Sub