dotnet-sdk/examples/Workflow/WorkflowConsoleApp/Activities/UpdateInventoryActivity.cs

using System.Threading.Tasks;
using Dapr.Client;
using Dapr.Workflow;
using WorkflowConsoleApp.Models;
using Microsoft.Extensions.Logging;

namespace WorkflowConsoleApp.Activities
{
    class UpdateInventoryActivity : WorkflowActivity<PaymentRequest, object>
    {
        static readonly string storeName = "statestore";
        readonly ILogger logger;
        readonly DaprClient client;

        public UpdateInventoryActivity(ILoggerFactory loggerFactory, DaprClient client)
        {
            this.logger = loggerFactory.CreateLogger<UpdateInventoryActivity>();
            this.client = client;
        }

        public override async Task<object> RunAsync(WorkflowActivityContext context, PaymentRequest req)
        {
            this.logger.LogInformation(
                "Checking inventory for order '{requestId}' for {amount} {name}",
                req.RequestId,
                req.Amount,
                req.ItemName);

            // Simulate slow processing
            await Task.Delay(TimeSpan.FromSeconds(5));

            // Determine if there are enough Items for purchase
            InventoryItem item = await client.GetStateAsync<InventoryItem>(
                storeName,
                req.ItemName.ToLowerInvariant());
            int newQuantity = item.Quantity - req.Amount;
            if (newQuantity < 0)
            {
                this.logger.LogInformation(
                    "Payment for request ID '{requestId}' could not be processed. Insufficient inventory.",
                    req.RequestId);
                throw new InvalidOperationException();
            }

            // Update the statestore with the new amount of the item
            await client.SaveStateAsync(
                storeName,
                req.ItemName.ToLowerInvariant(),
                new InventoryItem(Name: req.ItemName, PerItemCost: item.PerItemCost, Quantity: newQuantity));

            this.logger.LogInformation(
                "There are now {quantity} {name} left in stock",
                newQuantity,
                item.Name);

            return null;
        }
    }
}