Adding array of int to database in Entity Framework Core

Question

I want to make an API that can receive any number of child IDs. and loop it in database adding 1 row for each child IDs. I tried making the CategoryChildId a list or array but it says Entity framework does not accept primitive types.

How can i achieve this?

for example when i receive a json like this:

"CategoryParentID": "4",
"CategoryChildID": [
    {
      5,6,7
    }
  ],

It will store it in database like this.

I only have the code for adding single child at a time.

The service for the controller:

 public async Task<ServiceResultWithoutBaseEntity<CategoryRollup>> Add(CategoryRollupViewModel newItem)
{
    var result = new ServiceResultWithoutBaseEntity<CategoryRollup>();
    result.Errors.AddRange(Validate(newItem));

    if (result.HasErrors)
        return result;

    var item = newItem.MapToEntity(new CategoryRollup());

    _context.CategoryRollups.Add(item);
    await _context.SaveChangesAsync();

    result.EntityResult = item;

    return result;
}

model:

    public class CategoryRollup
{
    [Key]
    public int ID { get; set; }

    public int CategoryChildID { get; set; }

    public int CategoryParentID { get; set; }
}

view model:

public class CategoryRollupViewModel
{
    [Key]
    public int ID { get; set; }

    public int CategoryChildID { get; set; }

    public int CategoryParentID { get; set; }

}

helper:

  public static class CategoryRollupHelper
{
    public static CategoryRollupViewModel MapFromEntity(this CategoryRollup source)
    {
        if (source == null)
            return null;

        var result = new CategoryRollupViewModel
        {
            CategoryChildID = source.CategoryChildID,
            CategoryParentID = source.CategoryParentID,
        };

        return result;
    }

    public static CategoryRollup MapToEntity(this CategoryRollupViewModel source, CategoryRollup entity)
    {
        if (source == null || entity == null)
            return null;

        entity.CategoryChildID = source.CategoryChildID;
        entity.CategoryParentID = source.CategoryParentID;

        return entity;
    }
}

Make your API accept an object which has one of its attributes as a list of integer, then pass you Json to it. I believe you know how to loop the list and under into the db. — Bosco
– Bosco, Commented Jun 9, 2019 at 12:42
@Bosco i tried that but it is saying Entity framework does not accept primitive types. — user10860402
– user10860402, Commented Jun 9, 2019 at 12:46
Look at this stackoverflow.com/questions/3227525/… and any other Entity framework question related to "multiple inserts" — mode_x
– mode_x, Commented Jun 9, 2019 at 12:57

Florin-Constantin Ciubotariu · Accepted Answer · 2019-06-09 13:37:38Z

0

The JSON example is not valid. The CategoryChildID must hold an array of integers (drop the {}).

Lets suppose the JSON has the following structure:

"CategoryParentID": "4",
"CategoryChildID": [5,6,7]

That means your view model should contain two properties (create new class)

public class CategoryRollupViewModelV2
{

    public List<int> CategoryChildID { get; set; }

    public int CategoryParentID { get; set; }

}

Change your controller code to:

public async Task<ServiceResultWithoutBaseEntity<CategoryRollup>> Add(CategoryRollupViewModelV2 newItem)
{
    ...
    foreach(var categoryChildId in newItem.CategoryChildID)
    {
       var categoryRollupEntity = new CategoryRollup
       {
           CategoryParentID = newItem.CategoryParentID,
           CategoryChildID = categoryChildId
       }
       _context.CategoryRollups.Add(categoryRollupEntity);
    }
    await _context.SaveChangesAsync();
    ...
}

edited Jun 9, 2019 at 13:37

answered Jun 9, 2019 at 13:03

Florin-Constantin Ciubotariu

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8 Comments

user10860402 Over a year ago

EF core does not support List<int> i think. i get this error "because it is of type 'List<int>' which is not a supported primitive type or a valid entity type."

Florin-Constantin Ciubotariu Over a year ago

I didn't change the entity but the view model. Have you tested the code?

user10860402 Over a year ago

It is having an error in the helper code on the line " CategoryChildID = source.CategoryChildID," it says cannot implicitly convert type int to list. What shoud i changed it to? thanks. helper code is included in the question

Florin-Constantin Ciubotariu Over a year ago

Comment the helper method because it is not necessary anymore and we will not use it.

user10860402 Over a year ago

How about this line sir " var item = newItem.MapToEntity(new CategoryRollup());" item is included in your code. MapEntity is in helper

|

Alen.Toma · Accepted Answer · 2019-06-09 13:04:22Z

0

You will need to understand how EF ORM works.

Will redesign your module a little.

Lets say you have

public class CategoryRollup
{
    [Key]
    public int ID { get; set; }

    // Now i assume that CategoryChildID refer to a list of CategoryRollup as children
    // then just make it so. you may have to config this in moduleBuilder 
    public List<CategoryRollup> CategoryChildren { get; set; }

    /// and this is the parent
    public CategoryRollup CategoryParent { get; set; }
}

Now your model could look like this, its upp to you though

public class CategoryRollupViewModel
{

    public CategoryRollupViewModel(CategoryRollup item){
      ID = item.ID;
      CategoryChildID = item.CategoryChildren.Select(x=> x.ID).ToList();
      CategoryParentID = item.CategoryParent?.ID; 
    }
    [Key]
    public int ID { get; set; }

    public List<int> CategoryChildID { get; set; }

    public int CategoryParentID { get; set; }

}

Did i understand you right ?

answered Jun 9, 2019 at 13:04

Alen.Toma

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1 Comment

user10860402 Over a year ago

CategoryRollup is the model and table sir that includes The Child and Parent ID. I will test this sir thank you.

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