UpdateSequenceIdManager.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.EntityFrameworkCore;
using Nito.AsyncEx;

namespace YourProject
{
	public interface IUpdateSequenceIdManager	// you need to write your own implementation of this
	{
		Task<long> NextAsync();
		Task<long> CurrentAsync();
	}
	
	// This uses a MSSQL database backend with a very simple table to manage sequence number generation.
	// But, you need to write your own implementation of this. This one is not great.
	// CREATE TABLE [dbo].[tbl_UpdateSequenceIds](
	// 		[Name] [varchar](50) NULL,
	// 		[Id] [bigint] NULL
	// ) ON [PRIMARY]
	// GO
	// INSERT INTO [dbo].[tbl_UpdateSequenceIds] ([Name], [Id]) VALUES ('Current', 0)
	// GO
	public class UpdateSequenceIdManager : IUpdateSequenceIdManager
	{

		private readonly AzDPullRequestsDbContext _dbContext;
		private readonly AsyncReaderWriterLock _seqLock = new AsyncReaderWriterLock();

		public UpdateSequenceIdManager(YourProjectsDbContext dbContext)
		{
			_dbContext = dbContext;
		}

		public async Task<long> NextAsync()
		{
			using (await _seqLock.WriterLockAsync())
			{
				var sequenceRecord = await _dbContext.UpdateSequenceIds.FirstAsync(i => i.Name == "Current");

				var next = ++sequenceRecord.Id;

				await _dbContext.SaveChangesAsync();

				return next;
			}
		}

		public async Task<long> CurrentAsync()
		{
			using (await _seqLock.ReaderLockAsync())
			{
				var sequenceRecord = await _dbContext.UpdateSequenceIds.FirstAsync(i => i.Name == "Current");
				return sequenceRecord.Id;
			}
		}
	}
}