如何将事务与DbUpdateConcurrentException集成

我正在创建一个应用程序,它有多个客户端,可以更新相同的数据,所以我计划使用这种方法更新水果。将它们保存到数据库中,然后使用SignalR更新所有其他客户端。我正在努力设计代码以避免并发问题,所以我从 here 我想知道如何将事务与这段代码结合起来(我已经尝试过,但不确定它是否正确或必要)?或者因为它是为了处理并发性而设计的,我甚至需要事务吗?

为了创建并发问题,我将断点设置为 dbContext.SaveChanges(); 并更新数据库中的数据。

app.MapPut("UpdateFruits", async (string message, IHubContext<ChatHub> context, DatabaseContext dbContext) =>
{
    //message(Param) = { "ID":"2","DisplayName":"Fruit","Leaf":null,"State":"Chopped"}
    using var transaction = dbContext.Database.BeginTransaction();
    try
    {
        // Fetch a person from database and change phone number
        var fruit = dbContext.Set<Fruit>().Single(p => p.ID == 1);
        fruit.State = State.Chopped;
        fruit.DisplayName = "test";

        var saved = false;
        while (!saved)
        {
            try
            {
                // Attempt to save changes to the database
                dbContext.SaveChanges();
            
                saved = true;             
            }
            catch (DbUpdateConcurrencyException ex)
            {
                foreach (var entry in ex.Entries)
                {
                    if (entry.Entity is Fruit)
                    {
                        var proposedValues = entry.CurrentValues;
                        var databaseValues = entry.GetDatabaseValues();

                        foreach (var property in proposedValues.Properties)
                        {
                            var proposedValue = proposedValues[property];
                            var databaseValue = databaseValues[property];

                            // TODO: decide which value should be written to database
                            // proposedValues[property] = <value to be saved>;
                        }

                        // Refresh original values to bypass next concurrency check
                        entry.OriginalValues.SetValues(databaseValues);
                    }
                    else
                    {
                        throw new NotSupportedException(
                            "Don't know how to handle concurrency conflicts for "
                            + entry.Metadata.Name);                      
                    }
                }
            }
        }
        transaction.Commit();
        var jsonString = JsonConvert.SerializeObject(fruit);
        await context.Clients.All.SendAsync("ReceiveMessage", "FromServer", jsonString);
    }
    catch (Exception)
    {
        transaction.Rollback();
    }
    return Results.NoContent();
});

型号:

public class Fruit
{
    public int ID { get; set; }
    public string DisplayName { get; set; } = String.Empty;
    public List<Leaf>? Leaf{ get; set; }
}

public class Leaf
{
    public int ID { get; set; }
    public string DisplayName { get; set; } = String.Empty;
    public List<Vein>? Vein{ get; set; }
}

public class Vein
{
    public int ID { get; set; }
    public string DisplayName { get; set; } = String.Empty;
}

DBContext:

using EAS.API.PropertyManagement.Entities;
using GFX.Suite.API.GFX.Entities;
using Microsoft.EntityFrameworkCore;
using System.Collections;

namespace EAS.API.PropertyManagement.Core;

public class DatabaseContext : DbContext
{
    public DatabaseContext(DbContextOptions options) : base(options)
    {

    }
    Random rnd = new Random();
    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Fruit>(builder =>
        {

            builder.ToTable("Fruit");

            //builder.HasMany(c => c.Leaf)
            //.WithOne()
            //.HasForeignKey(f => f.LeafID);

            //var rendertypes = Enumerable
            // .Range(1, 5)
            // .Select(x => new Fruit
            // {
            //     ID = x,
            //     DisplayName = $"Fruits {x}",

            // })
            // .ToList();

            //builder.HasData(rendertypes);
        });

        modelBuilder.Entity<Leaf>(builder =>
        {

            builder.ToTable("Leaf");


            //var properties = Enumerable
            // .Range(1, 5)
            // .Select(x => new Leaf
            // {
            //     ID = x,
            //     DisplayName = $"Leaf {x}",
            // })
            // .ToList();

            //builder.HasData(properties);
        });

        modelBuilder.Entity<Vein>(builder =>
        {

            builder.ToTable("Vein");


            //var properties = Enumerable
            // .Range(1, 5)
            // .Select(x => new Vein
            // {
            //     ID = x,
            //     DisplayName = $"Vein {x}",
            // })
            // .ToList();

            //builder.HasData(properties);
        });
    }
}