microsoft/semantic-kernel · error · FileNotFoundException

File '{fileName}' not found.

Error message

File '{fileName}' not found.

What it means

Thrown by a helper that walks the directory tree upward from the current working directory searching for a named file. It checks each ancestor directory from CWD to the filesystem root; if the file is not found in any of them, it throws FileNotFoundException. The error is used to locate resource/config files shipped relative to the repo root.

Source

Thrown at dotnet/samples/Demos/OpenAIRealtime/Program.cs:393

            }
        }
    }

    /// <summary>Helper method to get a file path.</summary>
    private static string FindFile(string fileName)
    {
        for (string currentDirectory = Directory.GetCurrentDirectory();
             currentDirectory != null && currentDirectory != Path.GetPathRoot(currentDirectory);
             currentDirectory = Directory.GetParent(currentDirectory)?.FullName!)
        {
            string filePath = Path.Combine(currentDirectory, fileName);
            if (File.Exists(filePath))
            {
                return filePath;
            }
        }

        throw new FileNotFoundException($"File '{fileName}' not found.");
    }

    /// <summary>
    /// Helper method to get an instance of <see cref="RealtimeClient"/> based on provided
    /// OpenAI or Azure OpenAI configuration.
    /// </summary>
    private static RealtimeClient GetRealtimeConversationClient()
    {
        var config = new ConfigurationBuilder()
            .AddUserSecrets<Program>()
            .AddEnvironmentVariables()
            .Build();

        var openAIOptions = config.GetSection(OpenAIOptions.SectionName).Get<OpenAIOptions>()!;
        var azureOpenAIOptions = config.GetSection(AzureOpenAIOptions.SectionName).Get<AzureOpenAIOptions>()!;

        if (openAIOptions is not null && openAIOptions.IsValid)
        {

View on GitHub (pinned to c028a0c7dc)

Solutions

1. Verify the file actually exists somewhere under your repo or project tree, then run the app from a subdirectory of that tree.
2. Place the file in the application's base/output directory so the downward-from-root walk finds it, or copy it to the working directory.
3. Pass the full absolute path to the file directly instead of relying on the upward directory walk.
4. Embed the file as a project resource or content file with CopyToOutputDirectory so it ships with the build output.

Example fix

// before
throw new FileNotFoundException($"File '{fileName}' not found.");

// after — fall back to the application base directory
var basePath = AppContext.BaseDirectory;
var resolved = Path.Combine(basePath, fileName);
if (!File.Exists(resolved))
    throw new FileNotFoundException($"File '{fileName}' not found in {basePath} or any parent directory.");
return resolved;

// Check common locations before the upward walk
var candidates = new[] { AppContext.BaseDirectory, Directory.GetCurrentDirectory(), AppDomain.CurrentDomain.BaseDirectory };
var found = candidates.Select(d => Path.Combine(d, fileName)).FirstOrDefault(File.Exists);
if (found is null)
    found = SearchUpward(fileName); // your existing walk

try { return SearchUpwardForFile(fileName); } catch (FileNotFoundException) { /* log and use a default or embedded resource */ return EmbeddedResourcePath; }

When it happens

Trigger: Calling the file-search helper (e.g., GetFilePath) with a fileName that doesn't exist in the current directory or any ancestor directory — typical when the app is deployed or run from a directory that isn't nested under the repo, or when the target file was never copied to the output.

Common situations: Running the OpenAIRealtime sample from a published/packaged location where the config or assets file isn't present; running from /tmp or a container where the parent chain doesn't contain the file; the file name was renamed or the path convention changed between sample versions.

Related errors

• Plugins directory not found. The app needs the plugins from
• File {path} not found in repository.
• File {file_name} not found in repository.
• Configuration not found, please setup the notebooks first us
• Invalid choice

AI-assisted analysis of microsoft/semantic-kernel@c028a0c7dc (2026-08-13). Data as JSON: /api/errors/49f8cacd53a17724. Report an issue: GitHub.