How to use wkhtmltopdf Rotativa ViewAsPdf in Blazor Server

Question

I would like to use Rotativa.AspNetCore.ViewAsPdf("~/Views/MyView/PDF.cshtml", model) in Blazor Server the same way I do in regular ASP.NET CORE MVC apps.

1. I installed the "Rotativa.AspNetCore" nuget in my Blazor server project in .NET 8

2. Added RotativaConfiguration.Setup(app.Environment.WebRootPath); app.UseRotativa(); in Program.cs

3. Created a "Views" folder with a PDF.cshtml view

4. Created a Controller I am calling via httpClient from my razor component to generate the PDF

[HttpPost("exportPDF")]
public ActionResult ExportPDF(PDFModel model)
{

    return new Rotativa.AspNetCore.ViewAsPdf("~/Views/MyView/PDF.cshtml", model)
    {
        FileName = "MyFile" + DateTime.Now.ToString("yyyyMMddHHmmss") + ".pdf",
        PageSize = Rotativa.AspNetCore.Options.Size.A4,
        PageOrientation = Rotativa.AspNetCore.Options.Orientation.Portrait,
        PageMargins = { Left = 15, Right = 15, Top = 15 },
        CustomSwitches = "--footer-center \"MyDocument + "\" --footer-right \"Page: [page]/[toPage]\" --footer-font-size \"6\""
    };
}

And I am getting an "Object reference not set to an instance of an object." exception from the "Rotativa.AspNetCore" source.

Has anyone got this working in Blazor?

Answer 1

I got it working by myself. It is totally possible to use rotativa.exe and Rotativa.AspNetCore nuget to generate PDFs in Blazor using the "ViewAsPdf" method. My initial setup was good and I added following two controller methods:

public async Task<FileResult> ReturnPDF(int modelId)
{
    PDFModel model = new PDFModel(); //or load from db

    byte[] pdfBytes = await GetPDFBytes(model);

    return File(pdfBytes, "application/pdf");
}

which calls following that creates the pdf using rotativa:

public async Task<byte[]> GetPDFBytes(PDFModel model)
{

   var pdf =  new Rotativa.AspNetCore.ViewAsPdf("~/Views/PDF.cshtml", model)
   {
       FileName = "Export_" + DateTime.Now.ToString("yyyyMMddHHmmss") + ".pdf",
       PageSize = Rotativa.AspNetCore.Options.Size.A4,
       PageOrientation = Rotativa.AspNetCore.Options.Orientation.Portrait,
       PageMargins = { Left = 15, Right = 15, Top = 15 },
       CustomSwitches = "--footer-center \"ID_" + model.Id + "\" --footer-right \"Page: [page]/[toPage]\" --footer-font-size \"6\""
};

   byte[] pdfBytes = await pdf.BuildFile(this.ControllerContext);
   return pdfBytes;

}

and calling it from .razor component via:

<a href="@(_navManager.BaseUri + "mypage/ReturnPDF")" class="btn btn-danger" target="_blank">PDF_TEST_FileResult</a>

I have also tried creating an API controller and send it a post request with whole PDF model, but the PDF never displayed in the browser, but got returned to the calling object in razor code.