实体框架-访问本身具有外键/导航键的模型类

Question

I have the following Model, which can be a child of the same type, and/or have many children of the same type.

public class SystemGroupModel
    {
        public int Id { get; set; }

        public int? ParentSystemGroupModelId { get; set; }

        [ForeignKey("ParentSystemGroupModelId")]
        public virtual SystemGroupModel ParentSystemGroupModel { get; set; }

        [InverseProperty("ParentSystemGroupModel")]
        public virtual ICollection<SystemGroupModel> SubSystemGroupModels { get; set; }

    }

How can I get a specific SystemGroupModel by Id that is at an unknown depth, and include all of it's children, grandchildren, great-grandchildren, etc.?

Answer 1

This appears to be working, which means it will build a list of any given parent, as well as children at an unlimited depth of grandchildren, great-grandchildren, and so on.

Is this the right approach?

First I created this new class

public class SystemGroupWorkingClass
{
    public SystemGroupModel SystemGroupModel { get; set; }

    public bool WasChecked { get; set; }
}

Then I added this code
EDIT: Updated to include the loop that builds List<SystemGroupWorkingClass>

List<SystemGroupWorkingClass> tempListSystemGroups = new List<SystemGroupWorkingClass>();

//Get the SystemGroups that were selected in the View via checkbox
foreach (var systemGroupVM in viewModel.SystemGroups)
{
      if (systemGroupVM.Selected == true)
      {
           SystemGroupModel systemGroupModel = await db.SystemGroupModels.FindAsync(systemGroupVM.Id);

           SystemGroupWorkingClass systemGroupWorkingClass = new SystemGroupWorkingClass();
           systemGroupWorkingClass.SystemGroupModel = systemGroupModel;
           systemGroupWorkingClass.WasChecked = false;
           systemGroupWorkingClass.Selected = true;

           //Make sure tempListSystemGroups does not already have this systemGroupWorkingClass object
           var alreadyAddedCheck = tempListSystemGroups
                            .FirstOrDefault(s => s.SystemGroupModel.Id == systemGroupVM.Id);

           if (alreadyAddedCheck == null)
           {
               tempListSystemGroups.Add(systemGroupWorkingClass);
           }
       }
}


    for (int i = 0; i < tempListSystemGroups.Count; i++)
    {
        if (tempListSystemGroups[i].WasChecked == false)
        {
            SystemGroupModel systemGroupModel2 = await db.SystemGroupModels.FindAsync(tempListSystemGroups[i].SystemGroupModel.Id);

            //Get the children, if there are any, for the current parent
            var subSystemGroupModels = systemGroupModel2.SubSystemGroupModels
                    .ToList();

            //Loop through the children and add to tempListSystemGroups
            //The children are added to tempListSystemGroups as it is being iterated over
            foreach (var subSystemGroupModel in subSystemGroupModels)
            {
                SystemGroupModel newSystemGroupModel = await db.SystemGroupModels.FindAsync(subSystemGroupModel.Id);

                SystemGroupWorkingClass subSystemGroupWorkingClass = new SystemGroupWorkingClass();
                subSystemGroupWorkingClass.SystemGroupModel = newSystemGroupModel;
                subSystemGroupWorkingClass.WasChecked = false;

                tempListSystemGroups.Add(subSystemGroupWorkingClass);
            }
        }

        //Mark the parent as having been checked for children
        tempListSystemGroups[i].WasChecked = true;
    }