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using DevExpress.XtraReports.UI; |
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using DevExpress.XtraPrinting; |
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using DevExpress.XtraEditors; |
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public partial class MyReportViewerForm : XtraForm |
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{ |
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private XtraReport? _currentReport; |
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private CancellationTokenSource? _cts; |
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// Triggered by the Report's "Submit" button in the Parameters pane |
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private async void OnReport_ParametersRequestSubmit(object? sender, DevExpress.XtraReports.Parameters.ParametersRequestEventArgs e) |
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{ |
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// 1. Thread Safety: Cancel any ongoing report generation |
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_cts?.Cancel(); |
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_cts = new CancellationTokenSource(); |
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try |
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{ |
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// 2. Async Data Fetch (Generic Example) |
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var reportData = await FetchReportDataAsync(e.Parameters, _cts.Token) |
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.ConfigureAwait(ConfigureAwaitOptions.ContinueOnCapturedContext); |
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// 3. Re-initialize and Bind |
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await RefreshReportDisplayAsync(reportData, _cts.Token); |
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} |
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catch (OperationCanceledException) { /* Ignored */ } |
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catch (Exception ex) |
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{ |
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XtraMessageBox.Show($"Error loading report: {ex.Message}", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error); |
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} |
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} |
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private async Task RefreshReportDisplayAsync(object? dataSource, CancellationToken ct) |
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{ |
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// Prevent memory leaks: Unsubscribe and Dispose old report instance |
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if (_currentReport != null) |
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{ |
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_currentReport.ParametersRequestSubmit -= OnReport_ParametersRequestSubmit; |
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_currentReport.Dispose(); |
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} |
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// Initialize your specific XtraReport class |
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_currentReport = new MyXtraReport(); |
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_currentReport.ParametersRequestSubmit += OnReport_ParametersRequestSubmit; |
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// Assign fetched data |
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_currentReport.DataSource = dataSource; |
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// 4. Generate the document in the background |
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await _currentReport.CreateDocumentAsync(ct).ConfigureAwait(ConfigureAwaitOptions.ContinueOnCapturedContext); |
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// 5. Swap the PrintingSystem to refresh the DocumentViewer |
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UpdateDocumentViewer(); |
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} |
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private void UpdateDocumentViewer() |
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{ |
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if (_currentReport == null) return; |
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// We use ReportPrintTool to safely extract the PrintingSystem |
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using ReportPrintTool tool = new(_currentReport); |
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documentViewer1.PrintingSystem?.Dispose(); |
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documentViewer1.PrintingSystem = tool.PrintingSystem; |
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} |
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private async Task<object?> FetchReportDataAsync(parameterCollection params, CancellationToken token) |
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{ |
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// Your DB logic here |
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return await Task.FromResult<object?>(null); |
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} |
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} |
