microsoft/semantic-kernel · error · InvalidOperationException

Could not determine the assembly path.

Error message

Could not determine the assembly path.

What it means

Thrown in the relative-path branch when Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location) returns null. This indicates the assembly has no file location (e.g. loaded from a single-file publish bundle, in-memory, or a dynamic assembly), so the renderer cannot derive a base output folder.

Source

Thrown at dotnet/samples/GettingStartedWithProcesses/Utilities/MermaidRenderer.cs:50

        {
            // Use the provided absolute path
            outputFilePath = filenameOrPath;

            // Ensure the directory exists
            string directoryPath = Path.GetDirectoryName(outputFilePath)
                ?? throw new InvalidOperationException("Could not determine the directory path.");
            if (!Directory.Exists(directoryPath))
            {
                throw new DirectoryNotFoundException($"The directory '{directoryPath}' does not exist.");
            }
        }
        else
        {
            // Use the assembly's directory for relative paths
            string? assemblyPath = Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location);
            if (assemblyPath == null)
            {
                throw new InvalidOperationException("Could not determine the assembly path.");
            }

            string outputPath = Path.Combine(assemblyPath, "output");
            Directory.CreateDirectory(outputPath); // Ensure output directory exists
            outputFilePath = Path.Combine(outputPath, filenameOrPath);
        }

        // Download Chromium if it hasn't been installed yet
        BrowserFetcher browserFetcher = new();
        browserFetcher.Browser = SupportedBrowser.Chrome;
        await browserFetcher.DownloadAsync();

        // Define the HTML template with Mermaid.js CDN
        string htmlContent = $@"
        <html>
            <head>
                <style>
                    body {{

View on GitHub (pinned to c028a0c7dc)

Solutions

  1. Pass an absolute path so the relative branch is skipped entirely.
  2. Use AppContext.BaseDirectory instead of Assembly.Location in caller setup, and pass an absolute path built from it.

Example fix

// before
await MermaidRenderer.GenerateMermaidImageAsync(code, "diagram.png"); // fails under single-file publish
// after
string abs = Path.Combine(AppContext.BaseDirectory, "output", "diagram.png");
await MermaidRenderer.GenerateMermaidImageAsync(code, abs);
Defensive patterns

Strategy: validation

Validate before calling

string baseDir = !string.IsNullOrEmpty(Assembly.GetExecutingAssembly().Location)
    ? Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location)!
    : AppContext.BaseDirectory;
string abs = Path.Combine(baseDir, "output", filename);
await MermaidRenderer.GenerateMermaidImageAsync(code, abs);

Type guard

bool HasAssemblyLocation() => !string.IsNullOrEmpty(Assembly.GetExecutingAssembly().Location);

Try / catch

try { await MermaidRenderer.GenerateMermaidImageAsync(code, filename); }
catch (InvalidOperationException ex) when (ex.Message.Contains("assembly path")) { /* pass an absolute path built from AppContext.BaseDirectory */ }

Prevention

When it happens

Trigger: Calling GenerateMermaidImageAsync with a relative filename when the executing assembly's Location is empty (single-file app, in-memory load, AppContext.BaseDirectory-only host).

Common situations: Publishing as a single-file executable; running tests where the assembly is loaded in-memory; container/scenarios where Location is not set.

Related errors

AI-assisted analysis of microsoft/semantic-kernel@c028a0c7dc (2026-08-13). Data as JSON: /api/errors/1184b18c8444e0ee. Report an issue: GitHub.