我使用valueinjector nuget注入绑定模型到数据库实体使用如下:

public async Task<IHttpActionResult> Add(CustomBindingModel model)
{
   var entity= await db.MyEntities.FindAsync(model.Id);
   if (entity== null) return NotFound();

   entity.InjectFrom<NoNullsInjection>(model);

   await db.SaveChangesAsync();
   return Ok();
}

注意使用自定义约定，如果属性在服务器上为空，则不更新属性。

ValueInjecter v3 +

public class NoNullsInjection : LoopInjection
{
    protected override void SetValue(object source, object target, PropertyInfo sp, PropertyInfo tp)
    {
        if (sp.GetValue(source) == null) return;
        base.SetValue(source, target, sp, tp);
    }
}

用法:

target.InjectFrom<NoNullsInjection>(source);

值注入器V2

查找这个答案

警告

您将不知道该属性是被故意清除为null还是它只是没有任何值。换句话说，属性值只能被替换为另一个值，而不能被清除。

我用这个:

实体:

public class Thing 
{
    [Key]
    public int Id { get; set; }
    public string Info { get; set; }
    public string OtherStuff { get; set; }
}

数据库上下文：

public class MyDataContext : DbContext
{
    public DbSet<Thing > Things { get; set; }
}

访问器代码:

MyDataContext ctx = new MyDataContext();

// FIRST create a blank object
Thing thing = ctx.Things.Create();

// SECOND set the ID
thing.Id = id;

// THIRD attach the thing (id is not marked as modified)
db.Things.Attach(thing); 

// FOURTH set the fields you want updated.
thing.OtherStuff = "only want this field updated.";

// FIFTH save that thing
db.SaveChanges();

_context.Users.UpdateProperty(p => p.Id, request.UserId, new UpdateWrapper<User>()
                {
                    Expression = p => p.FcmId,Value = request.FcmId
                });
   await _context.SaveChangesAsync(cancellationToken);

Update Property是一个扩展方法

public static void UpdateProperty<T, T2>(this DbSet<T> set, Expression<Func<T, T2>> idExpression,
            T2 idValue,
            params UpdateWrapper<T>[] updateValues)
            where T : class, new()
        {
            var entity = new T();
            var attach = set.Attach(entity);
            attach.Property(idExpression).IsModified = false;
            attach.Property(idExpression).OriginalValue = idValue;
            foreach (var update in updateValues)
            {
                attach.Property(update.Expression).IsModified = true;
                attach.Property(update.Expression).CurrentValue = update.Value;
            }
        }

Update Wrapper是一个类

public class UpdateWrapper<T>
    {
        public Expression<Func<T, object>> Expression  { get; set; }
        public object Value { get; set; }
    }

I know this is an old thread but I was also looking for a similar solution and decided to go with the solution @Doku-so provided. I'm commenting to answer the question asked by @Imran Rizvi , I followed @Doku-so link that shows a similar implementation. @Imran Rizvi's question was that he was getting an error using the provided solution 'Cannot convert Lambda expression to Type 'Expression> [] ' because it is not a delegate type'. I wanted to offer a small modification I made to @Doku-so's solution that fixes this error in case anyone else comes across this post and decides to use @Doku-so's solution.

问题是Update方法中的第二个参数，

public int Update(T entity, Expression<Func<T, object>>[] properties). 

使用提供的语法调用此方法…

Update(Model, d=>d.Name, d=>d.SecondProperty, d=>d.AndSoOn); 

你必须在第二个参数前面加上'params'关键字。

public int Update(T entity, params Expression<Func<T, object>>[] properties)

或者如果你不想改变方法签名，那么要调用Update方法，你需要添加'new'关键字，指定数组的大小，然后最后使用集合对象初始化语法来更新每个属性，如下所示。

Update(Model, new Expression<Func<T, object>>[3] { d=>d.Name }, { d=>d.SecondProperty }, { d=>d.AndSoOn });

在@Doku-so的例子中，他指定了一个表达式数组，所以你必须在数组中传递属性来更新，因为数组你还必须指定数组的大小。为了避免这种情况，您还可以更改表达式参数，使用IEnumerable而不是数组。

下面是@Doku-so解决方案的实现。

public int Update<TEntity>(LcmsEntities dataContext, DbEntityEntry<TEntity> entityEntry, params Expression<Func<TEntity, object>>[] properties)
     where TEntity: class
    {
        entityEntry.State = System.Data.Entity.EntityState.Unchanged;

        properties.ToList()
            .ForEach((property) =>
            {
                var propertyName = string.Empty;
                var bodyExpression = property.Body;
                if (bodyExpression.NodeType == ExpressionType.Convert
                    && bodyExpression is UnaryExpression)
                {
                    Expression operand = ((UnaryExpression)property.Body).Operand;
                    propertyName = ((MemberExpression)operand).Member.Name;
                }
                else
                {
                    propertyName = System.Web.Mvc.ExpressionHelper.GetExpressionText(property);
                }

                entityEntry.Property(propertyName).IsModified = true;
            });

        dataContext.Configuration.ValidateOnSaveEnabled = false;

        return dataContext.SaveChanges();
    }

用法:

this.Update<Contact>(context, context.Entry(modifiedContact), c => c.Active, c => c.ContactTypeId);

@Doku-so提供了一种使用泛型的很酷的方法，我用这个概念来解决我的问题，但你不能使用@Doku-so的解决方案，在这篇文章和链接的帖子中，都没有人回答使用错误的问题。

新的EF Core 7原生功能- ExecuteUpdate:

终于!经过漫长的等待，EF Core 7.0现在有一个本地支持的方式来运行UPDATE(也删除)语句，同时还允许您使用任意的LINQ查询(。其中(u =>…))，而无需首先从数据库中检索相关实体:新的内置方法称为ExecuteUpdate -参见“EF Core 7.0有什么新功能?”

ExecuteUpdate正是针对这些场景的，它可以对任何IQueryable实例进行操作，并允许您在任意数量的行上更新特定的列，同时始终在幕后发出单个update语句，使其尽可能高效。

用法:

让我们以OP为例——即更新特定用户的密码列:

dbContext.Users
    .Where(u => u.Id == someId)
    .ExecuteUpdate(b =>
        b.SetProperty(u => u.Password, "NewPassword")
    );

如您所见，调用ExecuteUpdate需要调用SetProperty方法，以指定要更新的属性，以及要给它赋什么新值。

EF Core会将此转换为以下UPDATE语句:

UPDATE [u]
    SET [u].[Password] = "NewPassword"
FROM [Users] AS [u]
WHERE [u].[Id] = someId

另外，ExecuteDelete用于删除行:

ExecuteUpdate还有一个名为ExecuteDelete的对应程序，顾名思义，它可用于一次删除单个或多个行，而无需首先获取它们。

用法:

// Delete users that haven't been active in 2022:
dbContext.Users
    .Where(u => u.LastActiveAt.Year < 2022)
    .ExecuteDelete();

类似于ExecuteUpdate, ExecuteDelete将在幕后生成DELETE SQL语句——在本例中，是以下语句:

DELETE FROM [u]
FROM [Users] AS [u]
WHERE DATEPART(year, [u].[LastActiveAt]) < 2022

另注:

Keep in mind that both ExecuteUpdate and ExecuteDelete are "terminating", meaning that the update/delete operation will take place as soon as you call the method. You're not supposed to call dbContext.SaveChanges() afterwards. If you're curious about the SetProperty method, and you're confused as to why ExectueUpdate doesn't instead receive a member initialization expression (e.g. .ExecuteUpdate(new User { Email = "..." }), then refer to this comment (and the surrounding ones) on the GitHub issue for this feature. Furthermore, if you're curious about the rationale behind the naming, and why the prefix Execute was picked (there were also other candidates), refer to this comment, and the preceding (rather long) conversation. Both methods also have async equivalents, named ExecuteUpdateAsync, and ExecuteDeleteAsync respectively.

在实体框架核心中，Attach返回条目，所以你所需要的是:

var user = new User { Id = userId, Password = password };
db.Users.Attach(user).Property(x => x.Password).IsModified = true;
db.SaveChanges();