dotnet/efcore · error · OperationException

You must provide a DbContext.t4 file in order to scaffold us

Error message

You must provide a DbContext.t4 file in order to scaffold using custom templates.

What it means

Thrown when scaffolding with custom templates is requested for a language other than C# but no DbContext.t4 is supplied. EF Core only ships a built-in fallback DbContext generator for C# (CSharpDbContextGenerator); for any other language the user must provide the DbContext.t4 template.

Source

Thrown at src/EFCore.Design/Scaffolding/Internal/TextTemplatingModelGenerator.cs:115

                { "ProjectDefaultNamespace", options.RootNamespace }
            }
        };
        var contextTemplate = Path.Combine(options.ProjectDir!, TemplatesDirectory, DbContextTemplate);

        string generatedCode;
        if (File.Exists(contextTemplate))
        {
            host.TemplateFile = contextTemplate;

            generatedCode = Engine.ProcessTemplateAsync(File.ReadAllText(contextTemplate), host).GetAwaiter().GetResult();
            CheckEncoding(host.OutputEncoding);
            HandleErrors(host);
        }
        else
        {
            if (!string.Equals(options.Language, "C#", StringComparison.OrdinalIgnoreCase))
            {
                throw new OperationException(DesignStrings.NoContextTemplate);
            }

            var defaultContextTemplate = new CSharpDbContextGenerator { Host = host, Session = host.Session };
            defaultContextTemplate.Initialize();

            generatedCode = defaultContextTemplate.TransformText();

            foreach (CompilerError error in defaultContextTemplate.Errors)
            {
                _reporter.Write(error);
            }

            if (defaultContextTemplate.Errors.HasErrors)
            {
                throw new OperationException(DesignStrings.ErrorGeneratingOutput(defaultContextTemplate.GetType().Name));
            }
        }

View on GitHub (pinned to 3a2006ef56)

Solutions

1. Provide a DbContext.t4 template authored for the target language (VB.NET / F#).
2. Set options.Language to "C#" if C# output is acceptable, to use the built-in fallback generator.
3. Use a community template pack that ships DbContext.t4 for VB.NET/F# scaffolding.

Example fix

// before
options.Language = "VB";   // no DbContext.t4 present
// after - option A: supply template
//   CodeTemplates/EFCore/DbContext.t4   (VB version)
// after - option B: use C# fallback
options.Language = "C#";

bool isCSharp = string.Equals(options.Language, "C#", StringComparison.OrdinalIgnoreCase);
bool hasCtxTemplate = File.Exists(contextTemplate);
if (!isCSharp && !hasCtxTemplate)
    throw new InvalidOperationException("Provide DbContext.t4 for non-C# languages");

When it happens

Trigger: In GenerateModel, options.Language is not "C#" (case-insensitive) and no DbContext.t4 file exists at the expected template path, so the else branch throws NoContextTemplate.

Common situations: Attempting to scaffold VB.NET or F# contexts without supplying custom templates. Forgetting to ship the DbContext.t4 alongside the rest of a VB/F# template set. Setting options.Language to a non-C# value by accident.

Related errors

• Failed to resolve type for directive processor {name}.
• You've provided an EntityTypeConfiguration.t4 file without a
• The property '{property}' of the argument '{argument}' canno
• Processing '{inputFile}' failed.
• The project language '{language}' isn't supported by the bui

AI-assisted analysis of dotnet/efcore@3a2006ef56 (2026-08-11). Data as JSON: /api/errors/0321ab873038ae4e. Report an issue: GitHub.