Monnify .NET SDK

An idiomatic .NET SDK for the Monnify payment gateway API, targeting netstandard2.0 and net8.0.

Status: early release (pre-1.0). Published on NuGet.org starting with 0.1.0 — the public API may still change before a stable 1.0. See docs/COMPATIBILITY.md for every endpoint this SDK calls and how it was verified.

Features

• Collections — hosted checkout, reserved (virtual) accounts, invoices, bank-transfer payment links, transaction search
• Disbursements — single and bulk transfers, OTP authorization, wallet balance, transaction search
• Bills payment — airtime, data, cable TV, electricity, and other billers
• Verification — account name enquiry, BVN/NIN checks
• Banks — bank list, USSD-enabled banks
• Webhooks — signature verification, typed event parsing for all 12 documented event types
• One AddMonnify(...) call registers every typed client via Microsoft.Extensions.DependencyInjection
• Nullable reference types and CancellationToken on every async method

Install

dotnet add package Monnify

Configure

using Monnify;

builder.Services.AddMonnify(options =>
{
    options.ApiKey = "<your API key>";
    options.SecretKey = "<your secret key>";
    options.Environment = MonnifyEnvironment.Sandbox; // or MonnifyEnvironment.Live
});

This registers IMonnifyCollectionsClient, IMonnifyDisbursementsClient, IMonnifyBillsClient, IMonnifyVerificationClient, IMonnifyBanksClient, and the MonnifyClient facade that aggregates all of them — inject whichever you need.

Usage

The examples below assume collections, disbursements, bills, verification, and banks are constructor-injected via the interfaces registered above (e.g. a constructor parameter of type IMonnifyCollectionsClient collections).

Collect a payment

var checkout = await collections.InitializeTransactionAsync(new InitializeTransactionRequest
{
    Amount = 1000,
    CustomerName = "Jane Doe",
    CustomerEmail = "jane.doe@example.com",
    PaymentReference = Guid.NewGuid().ToString("N"),
    PaymentDescription = "Order #1234",
    ContractCode = "<your contract code>",
});

// Redirect the customer to checkout.CheckoutUrl

Send money

var transfer = await disbursements.InitiateSingleTransferAsync(new SingleTransferRequest
{
    Amount = 5000,
    Reference = Guid.NewGuid().ToString("N"),
    Narration = "Refund for order #1234",
    DestinationBankCode = "058",
    DestinationAccountNumber = "0123456789",
    DestinationAccountName = "Jane Doe",
    SourceAccountNumber = "<your Monnify wallet account number>",
});

A failed or ambiguous transfer should never be blindly retried with the same reference — see the remarks on IMonnifyDisbursementsClient for the safe retry pattern (query status first; only retry with a new reference).

Pay a bill

Some products (electricity prepaid plans, for example) require validating the customer first, which returns a ValidationReference to pass into the vend request — check VendInstruction.RequireValidationRef to know if a given product needs this step:

var validation = await bills.ValidateCustomerAsync(new ValidateBillCustomerRequest
{
    ProductCode = "product-ikedc-pre",
    CustomerId = "55555666666",
});

var requiresValidation = validation.VendInstruction?.RequireValidationRef == true;

var vend = await bills.VendAsync(new VendBillRequest
{
    ProductCode = "product-ikedc-pre",
    CustomerId = "55555666666",
    Amount = 500,
    Reference = Guid.NewGuid().ToString("N"),
    ValidationReference = requiresValidation ? validation.VendInstruction!.ValidationReference : null,
});

Products that don't need validation (airtime top-ups, for example) can skip straight to VendAsync and leave ValidationReference unset.

Verify an account

var account = await verification.ValidateAccountNumberAsync("0123456789", "044");
// account.AccountName

List banks

var allBanks = await banks.GetBanksAsync();

Receive webhooks

app.MapPost("/webhooks/monnify", async (HttpRequest request, ILogger<Program> logger) =>
{
    var validation = await request.ValidateMonnifyWebhookAsync(secretKey);
    if (!validation.IsValid)
    {
        return Results.Unauthorized();
    }

    var envelope = validation.GetEnvelope();
    if (envelope.EventType == MonnifyWebhookEventTypes.SuccessfulTransaction)
    {
        var data = MonnifyWebhookParser.ParseEventData<CollectionTransactionEventData>(envelope);
        // ... record the payment
    }

    return Results.Ok(); // acknowledge immediately; do slow work out of band
});

Note: our sandbox sends no monnify-signature header at all, so IsValid is always false there by design — see the remarks on MonnifyWebhookValidator.

Error handling

Every client throws MonnifyApiException (carrying ResponseCode, ResponseMessage, HttpStatusCode, and RawResponseBody) when Monnify reports a failure, rather than returning a null or empty result — payments are a domain where a silently swallowed failure is dangerous.

try
{
    await collections.InitializeTransactionAsync(request);
}
catch (MonnifyApiException ex)
{
    logger.LogError("Monnify rejected the request: {Code} - {Message}", ex.ResponseCode, ex.ResponseMessage);
}

Full runnable samples

• samples/Monnify.Samples.ConsoleApp — DI via the generic host outside ASP.NET Core, listing banks and initializing a checkout.
• samples/Monnify.Samples.WebApi — a minimal API webhook receiver with signature verification and event dispatch.

Both read credentials from environment variables; see the comment at the top of each Program.cs for which ones to set.

Documentation

• docs/COMPATIBILITY.md — every SDK method against the Monnify endpoint it calls, and how it was verified
• CHANGELOG.md

Contributing

See CONTRIBUTING.md (also covers versioning and the release process). Security issues: see SECURITY.md.

License

MIT