Collect Rendering and Export Warnings
Collect a real missing-font export warning and distinguish a completed conversion with warnings from a failed corrupt-file conversion.
Run the example
Download the complete project, extract it, and run it with the .NET 8 SDK.
The project pins Aspose.Slides.NET6.CrossPlatform 26.10.0. The complete project uses portable image fixtures and the CrossPlatform package.
For the complete data assertions, set ASPOSE_LICENSE_PATH to your own valid license;
the visible helper loads it when supplied. Evaluation mode may truncate text or add watermarks.
dotnet restore Example.csproj
dotnet run --project Example.csproj --configuration Release --no-restore
The download contains Program.cs, Example.cs, the project,
dependency lock, and any JSON/CSV input. The helper source contains fixture generation,
license loading, serialization and assertions; it is part of the runnable project.
All presentation inputs are generated from original synthetic data. Results go to output/.
Example
using System;
using System.Collections.Generic;
using System.Collections.Concurrent;
using System.Diagnostics;
using System.Threading;
using System.Threading.Tasks;
using System.Drawing;
using System.Globalization;
using System.IO;
using System.IO.Compression;
using System.Linq;
using System.Text;
using System.Text.Json;
using Aspose.Slides;
using Aspose.Slides.Charts;
using Aspose.Slides.DOM.Ole;
using Aspose.Slides.Export;
using Aspose.Slides.LowCode;
using Aspose.Slides.Warnings;
internal static class Program
{
private static ExampleContext Context = null!;
private static Task<int> Main(string[] args) => ExampleBootstrap.RunAsync(args, async ctx =>
{
Context = ctx;
Example.Context = ctx;
ctx.BeginAction("optimization-batch/warnings/block-001");
RunExample();
string path=File.Exists("output/result.json")?"output/result.json":"result.json";
using var result=JsonDocument.Parse(File.ReadAllText(path));
var checks=new System.Collections.Generic.Dictionary<string,bool>();
if(ctx.IsLicensed)
{
using var expected=JsonDocument.Parse("{\"checks.font_warning_observed\":true,\"checks.warning_export_completed\":true,\"checks.corrupt_input_failed\":true,\"checks.error_not_reported_as_success\":true}");
foreach(var field in expected.RootElement.EnumerateObject())
{
var actual=result.RootElement;foreach(string part in field.Name.Split('.'))actual=actual.GetProperty(part);
ctx.Require(actual.ToString()==field.Value.ToString(),"Licensed assertion differs: "+field.Name);
checks["licensed-"+field.Name.Replace('.','-')]=true;
}
}
else
{
var values=result.RootElement.TryGetProperty("checks",out var nested)?nested:result.RootElement;
foreach(var field in values.EnumerateObject())if(field.Value.ValueKind==JsonValueKind.False)throw new InvalidOperationException("Evaluation assertion failed: "+field.Name);
checks["evaluation-semantic-effect"]=true;checks["evaluation-valid-output"]=true;
}
foreach(string pdf in Directory.GetFiles(".","*.pdf",SearchOption.AllDirectories))ctx.Require(File.ReadAllBytes(pdf).AsSpan(0,5).SequenceEqual(System.Text.Encoding.ASCII.GetBytes("%PDF-")),"Invalid PDF output.");
foreach(string png in Directory.GetFiles(".","*.png",SearchOption.AllDirectories)){var image=PortableImage.Decode(File.ReadAllBytes(png));ctx.Require(image.Width>0&&image.Height>0,"Empty PNG output.");}
ctx.Pass("optimization-batch/warnings/block-001",checks);
await Task.CompletedTask;
});
private sealed class Warnings : IWarningCallback
{
public List<object> Items {get;}=new();
public ReturnAction Warning(IWarningInfo warning){Items.Add(new{type=warning.WarningType.ToString(),description=warning.Description});return ReturnAction.Continue;}
}
private static void RunExample()
{
Example.Setup();using(var p=new Presentation())
{var shape=Example.Text(p.Slides[0].Shapes,"Text","Font substitution warning fixture");shape.TextFrame.Paragraphs[0].Portions[0].PortionFormat.LatinFont=new FontData("Example_Missing_Font_734991");p.Save("output/input.pptx",SaveFormat.Pptx);}
var warnings=new Warnings();using(var p=new Presentation("output/input.pptx")){p.Save("output/with-warning.pdf",SaveFormat.Pdf,new PdfOptions{WarningCallback=warnings});}
File.WriteAllBytes("output/corrupt.pptx",new byte[]{0x50,0x4b,3,4,0,0,0});string? error=null;
try{using var failed=new Presentation("output/corrupt.pptx",new LoadOptions{LoadFormat=LoadFormat.Pptx});failed.Save("output/should-not-exist.pdf",SaveFormat.Pdf);}catch(Exception ex){error=ex.GetType().Name+": "+ex.Message;}
Example.Require(warnings.Items.Count>0,"Missing-font warning was not observed.");Example.Require(error!=null&&!File.Exists("output/should-not-exist.pdf"),"Failed conversion reported success.");
Example.Json("output/report.json",new{successful_export_with_warnings=new{success=true,warnings=warnings.Items},failed_export=new{success=false,error}});
Example.Result(new{font_warning_observed=true,warning_export_completed=true,corrupt_input_failed=true,error_not_reported_as_success=true});
}
}
Expected result and checks
The program writes its semantic checks to output/result.json and throws if a required
result differs. Expected check values are:
{
"font_warning_observed": true,
"warning_export_completed": true,
"corrupt_input_failed": true,
"error_not_reported_as_success": true
}
The callback records WarningType and Description and returns Continue. Production applications should choose whether a warning is acceptable for their output requirements. A recoverable warning is not an error, and a failed file must not be recorded as successful. Configure fonts or substitution rules before retrying when typography matters.
Learn more
Open and run the complete project
Download the complete project, extract it and open Example.sln, or run:
dotnet restore Example.sln
dotnet run --project Example.csproj --configuration Release -- --mode evaluation
Use the current supported .NET 10 SDK/runtime. The project keeps a stable net8.0
target and accepts compatible stable SDKs; no exact SDK patch is required.
Evaluation runs without a license and explicitly ignores license environment settings.
It uses bounded fixtures and checks valid output while allowing the evaluation watermark
and documented read-back text truncation. For unrestricted checks, use --mode licensed
with your authorized ASPOSE_LICENSE_PATH. No license is included.
Inputs are copied from Fixtures into a separate output workspace. The program prints
the absolute output path; execution.json records the actual runtime and verified action.
The portable PNG helper creates original synthetic pixels without a Windows bitmap engine.
See setup and prerequisites for native libraries,
fonts, IDE settings and the .NET 8/9 runtime support boundary of 2026-11-10.