Add C# SDK (Pulumi.Esc.Sdk)

[dbeattie71]

Adds a C# SDK for the Pulumi ESC API, following the same generated + hand-written wrapper pattern as the Go, Python, and TypeScript SDKs.

What's included

Generated code (OpenAPI Generator 7.6.0, csharp / generichost library):

• Full async API client targeting net6.0
• All models with nullable reference types enabled
• DI-based IEscApi with IServiceCollection extensions

Hand-written wrappers:

• EscClient.cs — High-level convenience wrapper with ~30 methods, factory methods (Create, CreateDefault), IDisposable support
• EscAuth.cs — Reads credentials from PULUMI_ACCESS_TOKEN env var or ~/.pulumi/credentials.json (Pulumi CLI + ESC CLI paths)
• ValueMapper.cs — Recursive Value tree → plain .NET object unwrapping
• EnvironmentDefinitionSerializer.cs — YamlDotNet-based YAML ↔ EnvironmentDefinition serialization

Template overrides:

• partial_header.mustache — Pulumi copyright header on all generated files
• netcore_project.mustache — Custom .csproj with Pulumi branding, YamlDotNet dependency

Tests:

• 30 unit tests (EscAuth, ValueMapper, EnvironmentDefinitionSerializer)
• Integration test (full CRUD lifecycle, requires PULUMI_ACCESS_TOKEN + PULUMI_ORG)

Makefile targets:

• generate_csharp_client_sdk, build_csharp, test_csharp, test_csharp_integration

Method parity with Go SDK

Full parity with api_esc_extensions.go:

Category	Methods
Environments	CreateEnvironment, CloneEnvironment, DeleteEnvironment, ListEnvironments
Get/Update	GetEnvironment, GetEnvironmentAtVersion, GetEnvironmentYaml, GetEnvironmentAtVersionYaml, UpdateEnvironment, UpdateEnvironmentYaml
Open/Read	OpenEnvironment, OpenEnvironmentAtVersion, ReadOpenEnvironment, ReadOpenEnvironmentProperty, OpenAndReadEnvironment, OpenAndReadEnvironmentAtVersion
Decrypt	DecryptEnvironment, DecryptEnvironmentYaml
Validate	CheckEnvironment, CheckEnvironmentYaml
Revision tags	ListEnvironmentRevisionTags, ListEnvironmentRevisionTagsPaginated, GetEnvironmentRevisionTag, CreateEnvironmentRevisionTag, UpdateEnvironmentRevisionTag, DeleteEnvironmentRevisionTag
Environment tags	ListEnvironmentTags, ListEnvironmentTagsPaginated, GetEnvironmentTag, CreateEnvironmentTag, UpdateEnvironmentTag, DeleteEnvironmentTag
Revisions	ListEnvironmentRevisions, ListEnvironmentRevisionsPaginated

Bugs found and fixed in generated code

Bug	Root Cause	Fix
ReadOpenEnvironmentProperty returns 401	.NET Uri normalizes // → / in swagger path /open//{sessionID}	Wrapper calls ReadOpenEnvironment + navigates Value tree
UpdateEnvironmentYaml sends garbled YAML	JsonSerializer.Serialize(string) wraps YAML in JSON quotes	Wrapper sends raw YAML via direct HttpClient call
CreateEnvironment creates under wrong project	Generated constructor is (name, project) but intuitively called as (project, name)	Wrapper passes args in correct order
CheckEnvironmentYaml fails on Value deserialization	Swagger marks value as required on Value but API returns {\"unknown\":true} without it	Removed required check in Value.cs, protected via .openapi-generator-ignore

Usage

using Pulumi.Esc.Sdk;

using var client = EscClient.CreateDefault();

// Create an environment
await client.CreateEnvironmentAsync(\"myOrg\", \"myProject\", \"dev\");

// Update with YAML
await client.UpdateEnvironmentYamlAsync(\"myOrg\", \"myProject\", \"dev\",
    \"values:\\n  greeting: hello world\\n\");

// Open, resolve secrets, and read values
var (env, values) = await client.OpenAndReadEnvironmentAsync(\"myOrg\", \"myProject\", \"dev\");
Console.WriteLine(values[\"greeting\"]); // \"hello world\"

Checklist

• Builds clean on net6.0 (make build_csharp)
• 30 unit tests passing (make test_csharp)
• Full method parity with Go SDK
• .openapi-generator-ignore protects hand-written files
• README, CONTRIBUTING, CHANGELOG_PENDING updated
• Integration tests pass (make test_csharp_integration — requires API credentials)
• NuGet package publish workflow (future PR)

[tehsis]

Thank you very much for your contribution @dbeattie71 we trully appreciate it!

I'd be more than happy to merge your code once some issues are addressed.

1. Copyright notice is missing from a few files.

sdk/csharp/Pulumi.Esc.Sdk/Client/ApiResponseEventArgs.cs
sdk/csharp/Pulumi.Esc.Sdk/Client/ApiFactory.cs
sdk/csharp/Pulumi.Esc.Sdk/Api/IApi.cs
sdk/csharp/Pulumi.Esc.Sdk/Client/TokenBase.cs
sdk/csharp/Pulumi.Esc.Sdk/Client/JsonSerializerOptionsProvider.cs
sdk/csharp/Pulumi.Esc.Sdk/Client/CookieContainer.cs
sdk/csharp/Pulumi.Esc.Sdk/Client/ExceptionEventArgs.cs
sdk/csharp/Pulumi.Esc.Sdk/Client/TokenContainer.cs

They need to show the following notice: Copyright 2026, Pulumi Corporation. All rights reserved.

You can use pulumictl tool to validate them.

2. A few commited files don't match what the generator produces.
   We need to add Pulumi.Esc.Sdk/README.md. to .openapi-generator-ignore
   sdk/csharp/Pulumi.Esc.Sdk/Api/EscApi.cs seems to contain a blank line after the header comment

The latter should be fixed by running make generate_csharp_client_sdk and commit the result.

Let me know if you are able to address these issues.

Thanks!

[dbeattie71]

@tehsis Those issues should be fixed and validated with pulimictl

[tehsis]

Thanks @dbeattie71! I have rebased your work and addressed some issues (unrelated to this PR) at #118