Streaming PDF ASP NET Core

Streaming PDF and Other Formats in ASP.NET Core

When generating reports in a web application you typically want to stream the output directly to the HTTP response rather than writing a temporary file to disk. Use MemoryStreamGen for this.

NuGet packages

dotnet add package Majorsilence.Reporting.RdlEngine.SkiaSharp
dotnet add package Majorsilence.Reporting.RdlCri.SkiaSharp

Startup initialisation

Call RdlEngineConfig.RdlEngineConfigInit() once when the application starts, not inside each request handler.

// Program.cs
using Majorsilence.Reporting.Rdl;

var builder = WebApplication.CreateBuilder(args);
builder.Services.AddControllersWithViews();

var app = builder.Build();

// One time per app instance
RdlEngineConfig.RdlEngineConfigInit();

app.MapControllerRoute(name: "default", pattern: "{controller=Home}/{action=Index}/{id?}");
app.Run();

Stream a PDF response

using Majorsilence.Reporting.Rdl;
using Microsoft.AspNetCore.Mvc;

[HttpGet("report.pdf")]
public async Task<IActionResult> GetReportPdf()
{
    var rdlPath = Path.Combine(_env.ContentRootPath, "Reports", "MyReport.rdl");
    var rdlp = new RDLParser(await System.IO.File.ReadAllTextAsync(rdlPath))
    {
        Folder = Path.GetDirectoryName(rdlPath)
    };

    using var report = await rdlp.Parse();

    if (report.ErrorMaxSeverity > 4)
        return StatusCode(500, string.Join("; ", report.ErrorItems.Cast<string>()));

    await report.RunGetData(null);

    using var ms = new MemoryStreamGen();
    await report.RunRender(ms, OutputPresentationType.PDF);

    // Copy to byte array before MemoryStreamGen is disposed
    var pdf = ((System.IO.MemoryStream)ms.GetStream()).ToArray();
    return File(pdf, "application/pdf", "report.pdf");
}

Stream other formats

Change the OutputPresentationType value and MIME type to produce different formats. See Output Formats for the full list.

// Excel
using var ms = new MemoryStreamGen();
await report.RunRender(ms, OutputPresentationType.Excel2007);
var bytes = ((System.IO.MemoryStream)ms.GetStream()).ToArray();
return File(bytes, "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet", "report.xlsx");

// CSV
using var ms = new MemoryStreamGen();
await report.RunRender(ms, OutputPresentationType.CSV);
var bytes = ((System.IO.MemoryStream)ms.GetStream()).ToArray();
return File(bytes, "text/csv", "report.csv");

// HTML (embed in a page or return as a fragment)
using var ms = new MemoryStreamGen();
await report.RunRender(ms, OutputPresentationType.HTML);
var html = ms.GetText();
return Content(html, "text/html");

Pass parameters

// Set parameters on the viewer before RunGetData
var rdlp = new RDLParser(await System.IO.File.ReadAllTextAsync(rdlPath));
using var report = await rdlp.Parse();

// Parameters are passed as a dictionary to RunGetData
var parameters = new System.Collections.Generic.Dictionary<string, string>
{
    { "StartDate", "2024-01-01" },
    { "EndDate",   "2024-12-31" }
};

await report.RunGetData(parameters);

using var ms = new MemoryStreamGen();
await report.RunRender(ms, OutputPresentationType.PDF);
var pdf = ((System.IO.MemoryStream)ms.GetStream()).ToArray();
return File(pdf, "application/pdf", "report.pdf");

Pass a DataTable instead of a database query

using var report = await rdlp.Parse();

var rpt = report;
await rpt.DataSets["DataSetNameInYourReport"].SetData(yourDataTable);

using var ms = new MemoryStreamGen();
await report.RunGetData(null);
await report.RunRender(ms, OutputPresentationType.PDF);
var pdf = ((System.IO.MemoryStream)ms.GetStream()).ToArray();
return File(pdf, "application/pdf", "report.pdf");

Content-Type reference

Format	Content-Type
PDF	application/pdf
Excel (.xlsx)	application/vnd.openxmlformats-officedocument.spreadsheetml.sheet
CSV	text/csv
HTML	text/html
XML	application/xml
RTF	application/rtf
MHTML	message/rfc822
TIFF	image/tiff

Using the RdlAsp.Mvc package

For a higher-level route-based approach that lists and serves reports from a folder, see ASP.NET Core MVC.