Split collection linq entity framework

Question

I have a PropertyValues entity which reperesent product properties:

public enum Property { Color = 1, Brand, Size }

public class PropertyValue
{
    public int PropertyValueId { get; set; }
    public Property PropertyId { get; set; }
    public string Value { get; set; }

    public ICollection<Product> Products { get; set; }

    public PropertyValue()
    {
        Products = new HashSet<Product>();
    }
}

Cause we have end sequnce of product properties i created an enum Property which keep properties. I'm trying to achieve following result - to split collection depending on properties. Where the values are an another Dictionary

        Dictionary<Property, Dictionary<int, string>> dict = new Dictionary<Property, Dictionary<int, string>>()
        {
            new KeyValuePair<Property, Dictionary<int, string>>()
            {
                {
                    Property.Color,
                    new KeyValuePair<int, string>()
                    {
                        { 5, "white" }, // ProperyValueId, Value
                        { 6, "green"}
                    }
                }
            }
        }

I have been looked aside GroupBy and SelectMany, but didn't find a way. For now i have following:

            var query = await db.PropertyValues
            .OrderBy(prop => prop.PropertyId)
            .Where(prop => prop.PropertyId == Property.Brand)
            .ToDictionaryAsync(prop => prop.PropertyValueId, prop => prop.Value);

        Dictionary<Property, Dictionary<int, string>> properties = new Dictionary<Property, Dictionary<int, string>>();
        properties.Add(Property.Brand, query);

Should return a json. But firstly need to get sequence. Json should look like:

[{
{"colors": [{"5", "Black"}, {"7", "White"}]}, 
{"brands": [{"78", "Q&Q"}, {"24", "Adidas"}]},
}]

Answer 1

The first GroupBy splits the list of PropertyValues by PropertyId , then this grouping is converted to a dictionary that has PropertyId as Key.

The values of each record of our dictionary is composed by creating a new dictionary where the key is PropertyValueId and the value is Value

PropertyValues.GroupBy( k => k.PropertyId )
    .ToDictionary( k => k.First().Value, 
          k => k.ToDictionary( p => p.PropertyValueId, p => p.Value ) );

Now data is structured as you want.