I'm upgrading an older .NET framework ASP.NET MVC app to .NET 5. Can't seem to get EO.pdf's RenderAsPDF() function to work as it did with .NET framework. I've created a new ASP.NET MVC Core app using VS2019 and have done the following:

1. Added EO.Pdf.Mvc, System.Drawing.Common, System.Text.Encoding.CodePages nuget packages.
2. Called AddLicense()
3. Called RegisterFiltersAspNetCore as follows

services.AddControllersWithViews(options =>
{
//Register EO.Pdf MVCToPDF filters
EO.Pdf.Mvc.MVCToPDF.RegisterFilterAspNetCore(options);
});

4. Setup controller with RenderAsPDF() as follows

[EO.Pdf.Mvc.RenderAsPDF(AutoConvert = false)]
public IActionResult Index(string format)
{
if (!string.IsNullOrEmpty(format) && format.ToLower() == "pdf")
{
EO.Pdf.Mvc.MVCToPDF.ResultFileName = "eo-pdf.pdf";
EO.Pdf.Mvc.MVCToPDF.RenderAsPDF();
}

return View();
}

I get this exception.

fail: Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware[1]
An unhandled exception has occurred while executing the request.
System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation.
---> System.ArgumentNullException: Value cannot be null. (Parameter 'stream')
at Microsoft.AspNetCore.Http.StreamResponseBodyFeature..ctor(Stream stream, IHttpResponseBodyFeature priorFeature)
at Microsoft.AspNetCore.Http.DefaultHttpResponse.set_Body(Stream value)
--- End of inner exception stack trace ---
at System.RuntimeMethodHandle.InvokeMethod(Object target, Object[] arguments, Signature sig, Boolean constructor, Boolean wrapExceptions)
at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
at System.Reflection.RuntimePropertyInfo.SetValue(Object obj, Object value, BindingFlags invokeAttr, Binder binder, Object[] index, CultureInfo culture)
at System.Reflection.RuntimePropertyInfo.SetValue(Object obj, Object value, Object[] index)
at EO.Pdf.Mvc.MVCToPDF.vrlw.sjgr.fbjr()
at EO.Pdf.Mvc.MVCToPDF.dbei()
at EO.Pdf.Mvc.Emit.Filter.IResultFilter.OnResultExecuted(ResultExecutedContext )
at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.ResultNext[TFilter,TFilterAsync](State& next, Scope& scope, Object& state, Boolean& isCompleted)


Anything else I need do?

I'm using version 21.0.32. Is there working sample available that I could download? I don't see an ASP.NET Core sample included in the download.

Hi,

There isn't much to the working sample at all --- it's just an empty ASP.NET MVC project generated straight from the .NET Core MVC template. The issue appear to have something to do with something else in your application. The basic logic for MvcToPDF is like this:

1. At the beginning of the request, we would replace the default output stream (of type Microsoft.AspNetCore.Server.IIS.Core.HttpResponseStream);
2. ASP.NET Core would take our output stream. Both ASP.NET Core and EO.Pdf would save the original stream object;
3. At the end of the request, EO.Pdf would try to restore the original stream based to the saved value on step 2;
4. ASP.NET would compare this value with the value that it previously saved. If it does not match, then it will cause the error you received;

Thus it appears that in your application somebody else also replaced the output stream between step 2 and step 3. So if you can isolate it into a test project and send it to us, we can look into it and see if we can change our code to accommodate this situation. See here for information on sending test project to us:

https://www.essentialobjects.com/forum/test_project.aspx

Thanks!

Thank you very much for your test project. We were able to find out the root of the problem. This will be fixed in our next build.

You are welcome. We will reply here again when the new build is out.

That fixed it. Thanks for the quick turnaround.