dotnet/efcore · error · OperationException

No files were generated in directory '{outputDirectoryName}'

Error message

No files were generated in directory '{outputDirectoryName}'. The following file(s) already exist(s) and must be made writeable to continue: {readOnlyFiles}.

What it means

Thrown in CompiledModelScaffolder.WriteFiles (line 90, resource ReadOnlyFiles) when writing the compiled-model output files: some target files already exist and are marked read-only (FileAttributes.ReadOnly), so they cannot be overwritten. Rather than partially writing files, EF collects all read-only paths and throws an OperationException listing them. No files in the conflicting set are written.

Source

Thrown at src/EFCore.Design/Scaffolding/Internal/CompiledModelScaffolder.cs:90

        var savedFiles = new List<string>();
        foreach (var file in scaffoldedModel)
        {
            var fullPath = Path.Combine(outputDir, file.Path);

            if (File.Exists(fullPath)
                && File.GetAttributes(fullPath).HasFlag(FileAttributes.ReadOnly))
            {
                readOnlyFiles.Add(file.Path);
            }
            else
            {
                File.WriteAllText(fullPath, file.Code, new UTF8Encoding(encoderShouldEmitUTF8Identifier: false));
                savedFiles.Add(fullPath);
            }
        }

        return readOnlyFiles.Count != 0
            ? throw new OperationException(
                DesignStrings.ReadOnlyFiles(
                    outputDir,
                    string.Join(CultureInfo.CurrentCulture.TextInfo.ListSeparator, readOnlyFiles)))
            : (IReadOnlyList<string>)savedFiles;
    }
}

View on GitHub (pinned to dbf9771522)

Solutions

Clear the read-only attribute on the listed files (e.g. chmod +w / attrib -r) so they can be overwritten.
Delete the existing output files in the target directory before regenerating.
Use the scaffolder's force/overwrite option if invoking programmatically, or write to a fresh output directory.
If a VCS marks files read-only, ensure generated output is excluded from VCS or that the VCS is configured not to set read-only.

Example fix

# before: read-only files block generation
chmod u+w obj/CompiledModels/*.cs   # Linux/mac
attrib -r obj\CompiledModels\*.cs   # Windows

# then re-run
dotnet ef dbcontext optimize

Defensive patterns

Strategy: validation

Validate before calling

// Clear read-only attributes on existing output files before writing
foreach (var f in Directory.GetFiles(outputDir, "*.cs", SearchOption.AllDirectories))
    if ((File.GetAttributes(f) & FileAttributes.ReadOnly) != 0)
        File.SetAttributes(f, File.GetAttributes(f) & ~FileAttributes.ReadOnly);

Try / catch

try { CompiledModelScaffolder.WriteFiles(model, outputDir); }
catch (OperationException ex) when (ex.Message.Contains("must be made writeable"))
{ /* clear read-only flags on listed files or use a fresh directory, then retry */ }

Prevention

Generate into a clean directory or clear read-only flags first.
Exclude generated output from VCS systems that set read-only attributes.
Use the overwrite/force path when available.

When it happens

Trigger: Running compiled-model scaffolding into a directory where one or more output files already exist with the read-only attribute set. For each file, if File.Exists and attributes include ReadOnly, it is added to readOnlyFiles; if any exist at the end, the ReadOnlyFiles OperationException is thrown.

Common situations: Files checked into source control with read-only attributes (some VCS mark files read-only), or generated previously and then locked. Running on a filesystem/CI that marks output read-only. Re-running 'dotnet ef dbcontext optimize' without clearing previous read-only outputs.

Related errors

AI-assisted analysis of dotnet/efcore@dbf9771522 (2026-08-06). Data as JSON: /api/errors/bfd7661dae5b5e88. Report an issue: GitHub.