Insert multiple data in child table in ASP.NET Boilerplate

Background

I have two tables Actions and ActionsDetails.

Actions:

CREATE TABLE [dbo].[Actions]
(
    [ActionId] [BIGINT] IDENTITY(1,1) NOT NULL,
    [DeviceId] [NVARCHAR](125) NOT NULL,
    [TenantId] [INT] NOT NULL,

    CONSTRAINT [PK_ActionId]
        PRIMARY KEY CLUSTERED ([ActionId] ASC)
        WITH (STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF) ON [PRIMARY]
) ON [PRIMARY]

ActionsDetails:

CREATE TABLE [dbo].[ActionsDetails]
(
    [ActionsDetailsId] [BIGINT] IDENTITY(1,1) NOT NULL,
    [ActionId] [BIGINT] NOT NULL,
    [ActionName] [NVARCHAR](125) NOT NULL,
    [Description] [NVARCHAR](800) NOT NULL,

    CONSTRAINT [PK_ActionsDetailsId]
        PRIMARY KEY CLUSTERED ([ActionsDetailsId] ASC)
        WITH (STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF) ON [PRIMARY]
) ON [PRIMARY]
GO

ALTER TABLE [dbo].[ActionsDetails] WITH CHECK
    ADD CONSTRAINT [FK_ActionsDetails_ActionsId]
        FOREIGN KEY([ActionId]) REFERENCES [dbo].[Actions] ([ActionId])
GO

ALTER TABLE [dbo].[ActionsDetails] CHECK CONSTRAINT [FK_ActionsDetails_ActionsId]
GO

What I am trying to do is to insert a row of data in Actions and then capture ActionId for the inserted record, and then insert multiple values for that ActionId in ActionsDetails table. Very simple case of inserting into parent-child table using EF Core, just that child table can have multiple records for a parent row.

This is the piece of code which does that in ActionsAppService class:

public async Task CreateActions(CreateActionDto input)
{
    Actions actions = new Actions();
    ActionsDetails actionsdetails = new ActionsDetails();

    MapToEntity(input, actions);

    // Insert into Actions and return last generated ActionId

    long actionid = await _actionmanager.CreateActionsAsync(actions);

    // looping here since child table can have multiple record to be
    // inserted

    foreach (var actionname in input.ActionDetails)
    {
        // TODO: This can go to a mapping method as well
        actionsdetails.ActionName = actionname.ActionName;
        actionsdetails.Description = actionname.Description;
        actionsdetails.ActionId = actionid;

        // Inserting details into ActionsDetails table for the
        // corresponding ActionId

        await _actionmanager.CreateActionsDetailsAsync(actionsdetails);
    }
}

Data mapping between input DTO and entity:

private void MapToEntity(CreateActionDto actionsdto, Actions actions)
{
    actions.DeviceId = actionsdto.DeviceId;
    actions.TenantId = (int)(AbpSession.TenantId);
}

In ActionManager class:

public async Task<long> CreateActionsAsync(Actions input)
{
    return await _actionsRepository.InsertAndGetIdAsync(input);
}

public async Task CreateActionsDetailsAsync(ActionsDetails input)
{
    await _actionsdetailsRepository.InsertAsync(input);
}

Question

The issue that I am seeing is that ActionDetails list only contains last value of collection which is inserted. For example, if I pass this value:

{
  "deviceId": "zainnewdevice",
  "actionDetails": [
    {
      "actionId": 0,
      "actionName": "switchtube1",
      "description": "this would swtich on Tube1"
    },
    {
      "actionId": 0,
      "actionName": "switchtube2",
      "description": "This would switch on Tube2"
    }
  ]
}

The last value of collection, i.e. "switchtube2" and "This would switch on Tube2", is inserted in ActionDetails table.

Perhaps my way of getting things done is all wrong, or might be just my lack of understanding of Entity Framework and how it works, but I got a sense that the actionsdetails object needs to be added in context before calling the CreateActionsDetailsAsync in ActionManager. I couldn't figure out how to do it since all context is set in DbContext class.

Also, I was thinking maybe adding actionsdetails to a List and then passing that List object to CreateActionsDetailsAsync in ActionManager class would help. Perhaps I can loop through the list object there and call await _actionsdetailsRepository.InsertAsync(input) in a loop, but that strategy also failed.

DTO:

public class CreateActionDto
{
    [Required]
    public string DeviceId { get; set; }

    public ICollection<ActionsDetailsDto> ActionDetails { get; set; }
}

Entities:

public class Actions : Entity<long>, IMustHaveTenant
{
    [Column("ActionId")]
    [Key]
    public override long Id { get; set; }

    [Required]
    public string DeviceId { get; set; }

    [Required]
    public int TenantId { get; set; }

    public virtual ICollection<ActionsDetails> ActionsDetails { get; set; }

    public Actions()
    {
        ActionsDetails = new List<ActionsDetails>();
    }
}

public class ActionsDetails : Entity<long>
{
    [ForeignKey("ActionId")]
    public virtual Actions Actions { get; set; }

    [Column("ActionsDetailsId")]
    [Key]
    public override long Id { get; set; }

    [Required]
    public long ActionId { get; set; }

    [Required]
    public string ActionName { get; set; }

    [Required]
    public string Description { get; set; }
}

All rows in collection should appear in ActionsDetails table.