first commit

services/csharp/example/Features/Todos/ChangeTodoStatus.cs

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+using MediatR;
+using Microsoft.EntityFrameworkCore;
+using SequenceAuth.Example.Domain;
+using SequenceAuth.Example.Infrastructure;
+
+namespace SequenceAuth.Example.Features.Todos;
+
+public enum ChangeTodoStatusOutcome { Success, NotFound, Unauthorized }
+
+public record ChangeTodoStatusResult(ChangeTodoStatusOutcome Outcome, TodoItem? Item);
+
+public record ChangeTodoStatusCommand(Guid TodoId, Guid UserId, TodoStatus NewStatus) : IRequest<ChangeTodoStatusResult>;
+
+public class ChangeTodoStatusCommandHandler(AppDbContext dbContext) : IRequestHandler<ChangeTodoStatusCommand, ChangeTodoStatusResult>
+{
+    public async Task<ChangeTodoStatusResult> Handle(ChangeTodoStatusCommand request, CancellationToken cancellationToken)
+    {
+        var todo = await dbContext.Todos.FirstOrDefaultAsync(t => t.Id == request.TodoId, cancellationToken);
+        
+        return todo switch
+        {
+            null => new ChangeTodoStatusResult(ChangeTodoStatusOutcome.NotFound, null),
+            { UserId: var userId } when userId != request.UserId => new ChangeTodoStatusResult(ChangeTodoStatusOutcome.Unauthorized, null),
+            _ => await UpdateStatusAsync(todo, request.NewStatus, cancellationToken)
+        };
+    }
+
+    private async Task<ChangeTodoStatusResult> UpdateStatusAsync(TodoItem todo, TodoStatus newStatus, CancellationToken cancellationToken)
+    {
+        var updatedTodo = todo with { Status = newStatus };
+        
+        dbContext.Entry(todo).CurrentValues.SetValues(updatedTodo);
+        await dbContext.SaveChangesAsync(cancellationToken);
+        
+        return new ChangeTodoStatusResult(ChangeTodoStatusOutcome.Success, updatedTodo);
+    }
+}