.NET SDK

The .NET client (netstandard2.0 and net8.0) — typed requests and responses generated from the OpenAPI document, on HttpClient, plus a webhook signature verifier.

Getting it


Package	`Fin403.Transmute`
Namespaces	`Fin403.Transmute` (helpers), `Fin403.Transmute.Api`, `.Client`, `.Model`
Targets	`netstandard2.0` and `net8.0`
Dependencies	`Newtonsoft.Json`, `Polly`; HTTP is `System.Net.Http.HttpClient`

dotnet add package Fin403.Transmute --version X.Y.Z

The package version tracks the API release: X.Y.Z is generated from API release vX.Y.Z.

Not on NuGet yet. Until the first release is published, the package is provided during onboarding — contact support.

Convert a message

using Fin403.Transmute;
using Fin403.Transmute.Api;
using Fin403.Transmute.Model;

var http = TransmuteClient.CreateHttpClient();          // reuse one per process
var config = TransmuteClient.CreateConfiguration(
    "https://api.transmute.403fin.io",
    Environment.GetEnvironmentVariable("TRANSMUTE_KEY"));
var engine = new EngineApi(http, config);

var mt940 = string.Join("\r
",
    "{1:F01AAAADEFFXXXX0000000000}{2:I940BBBBDEFFXXXXN}{4:",
    ":20:STMT0001",
    ":25:DE89370400440532013000",
    ":28C:00042/001",
    ":60F:C260601EUR1000,00",
    ":61:2606020602C250,00NTRFNONREF//BANKREF1",
    ":86:INVOICE 4711",
    ":62F:C260602EUR1250,00",
    "-}");

var resp = await engine.ConvertMessageAsync(new ConvertRequest(
    to: "camt.053",
    message: mt940));                                   // from omitted → auto-detect

Console.WriteLine(resp.Meta.DetectedType);            // "mt940"
var camt053 = resp.Result.GetString();
foreach (var w in resp.Warnings)
    Console.WriteLine($"{w.Code} ({w.Severity}): {w.Detail}");

resp.Result holds one string (GetString()) or, when MT paging splits the output, a list (GetList(); Meta.Pages is then set). CreateConfiguration also accepts an OAuth access token in place of an API key. Errors throw ApiException: ErrorCode is the HTTP status and ErrorContent the RFC 9457 problem document, whose type slug is in the error catalog.

API version, Standards Release and envelope

Option	.NET	What it does
`X-Api-Version`	`TransmuteClient.CreateHttpClient(apiVersion: "2026-06-01")` for every request; the `xApiVersion:` argument on one call wins	Pins date-versioned behaviour — today, the default Standards Release. Unset: your API key's pin, else the current version. See Migrating from SR2025 to SR2026.
`srVersion`	`new ConvertOptions(srVersion: SRVersion.SR2026)` (also normalize, validate, batch)	Explicit Standards Release; always wins over the API version's default.
`envelope` (convert)	`new ConvertOptions(envelope: ConvertOptions.EnvelopeEnum.Apphdr)`; `Fin` for MT targets	`apphdr` adds a `head.001.001.02` Business Application Header before the MX `Document`; `fin` wraps MT output in FIN blocks 1 and 2.
`envelope` (normalize)	`new NormalizeOptions(envelope: NormalizeOptions.EnvelopeEnum.Include)`	Adds `result.envelope` (the source's FIN headers or Business Application Header).

Options you do not set are not sent (the boolean strict is always sent, as false unless you set it — the API's own default), so an unpinned client follows the API version policy.

Verify a webhook delivery

try
{
    WebhookSignature.Verify(
        endpointSecret,                                 // "whsec_..." — the full string
        Request.Headers["X-Transmute-Signature"],       // "t=...,v1=..."
        rawBody,                                        // raw bytes, read before parsing
        WebhookSignature.DefaultTolerance);             // 5 minutes
}
catch (WebhookSignatureException)
{
    return BadRequest();
}

Constant-time comparison and the replay-window check are built in — see Webhooks for the delivery contract.

Notes

Generated with openapi-generator (csharp, httpclient library) from the same OpenAPI document that serves api.transmute.403fin.io/docs, with the dashboard-internal portal routes removed; a CI gate keeps them in lockstep.
Amount fields are strings in all response types — parse with decimal, never double.

"SWIFT" is a trademark of S.W.I.F.T. SCRL. transmute converts SWIFT MT messages; it is not affiliated with, endorsed by, or certified by SWIFT.

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