This project is aimed at porting Microsoft Reporting Services (Report Viewer) to .NET Core 3.1+. This is still work-in-progress and not ready for production use.

With WinForms inclusion in .NET Core 3.1 and .NET 5 as a replacement for .NET Framework, it became feasible to port existing business desktop applications to .NET Core SDK to benefit from new C# and JIT features. Microsoft team stated on multiple occasions (dotnet/aspnetcore#1528, dotnet/aspnetcore#12666, dotnet/aspnetcore#22304, dotnet/docs#9607) that there are no plans to have official Reporting Services / ReportViewer package for .NET Core, which is a showstopper for applications using this technology for printing and reporting. The goal of this project is to provide transitional solution for such applications, until existing reports are reimplemented using more modern technology.

You should be able to replace references to Report Viewer in your WinForms project with ones provided in this repo and use Microsoft.Reporting.WinForms.ReportViewer as usual. See project ReportViewerCore.WinForms for a simplified example.

For ASP.NET Core applications, add reference to Microsoft.Reporting.NETCore, which is based on WinForms version with stripped UI and remote processing, and load/render report programmatically. See project ReportViewerCore.Console for an example or use following code as a starting point:

Stream reportDefinition; // your RDLC from file or resource
IEnumerable dataSource; // your datasource for the report

LocalReport report = new LocalReport();
report.LoadReportDefinition(reportDefinition);
report.DataSources.Add(new ReportDataSource("source", dataSource));
report.SetParameters(new[] { new ReportParameter("Parameter1", "Parameter value") });
byte[] pdf = report.Render("PDF");

Keep in mind each invocation of LoadReportDefinition loads new dynamic assembly. In long running applications this can degrade performance and/or lead to resource exhaustion. As a workaround, reuse instances of LocalReport. A more permanent fix would require changing Microsoft.ReportingServices.RdlExpressions.VBExpressionCodeProvider.CompileAssemblyFromDom method to cache compiled assemblies.

• RDLC file loading and compiling
• Local data sources
• Parameter passing
• PDF report rendering
• Microsoft Word rendering
• Microsoft Excel report rendering
• WinForms report preview

• Assembly unloading. Each invocation compiles and loads a dynamic assembly that stays in memory for the lifetime of a process. Where possible cache and reuse instance of LocalReport initialized by LoadReportDefinition.
• Spatial SQL types. Those require Microsoft.SqlServer.Types package, which is available only in .NET Framework. Reports using SqlGeography won't load.
• Expression sandboxing and code security. Do not load and run reports from untrusted sources.
• Interactive web report preview. It is closely tied to WebForms and ASP.NET architecture and porting it to ASP.NET Core would involve rewriting significant portions of the codebase.

• SQL Server data sources
• ODBC Data sources. Most likely won't work.
• Remote processing. Might work in WinForms, but it misses the point of the project. Completely stripped down in NETCore version.
• Linux support. Should work, but I wouldn't hold my breath.
• MSChart control
• Map control

Source code for this project comes from decompiling Report Viewer for WinForms, version 15.0.1404.0 using ILSpy. Original Reporting Services use external Visual Basic and System.CodeDom compilation, both of which are not available in .NET Core. Those have been replaced with Roslyn Visual Basic compiler. References to .NET Framework assemblies have been updated to NuGet packages where possible. References to unavailable assemblies, such as Microsoft.SqlServer.Types, have been removed along with functionalities that depend on them. Sources are intentionally left formatted as decompiled by ILSpy.

Project Microsoft.ReportViewer.WinForms is mostly one-to-one recompilation of original ReportViewer for WinForms. Project Microsoft.ReportViewer.NETCore is heavilly stripped down version suitable for web applications, web services and batch processing.

I'm not confident enough with technical and legal aspects of this project to provide ready-to-use, compiled and packaged version. Feel free to compile this project on your own. You'll need Visual Studio 2019 (Community version will do) and .NET Core SDK 3.1. Reference either Microsoft.ReportViewer.NETCore.dll or Microsoft.ReportViewer.WinForms.dll in your solution.

Reporting Services is a free Microsoft product. While decompiling and modifying it for compatibility reasons is legal in my local jurisdiction, redistributing modified version most likely is not. Use at your own risk.