C# Creating a unique list of rows from a LIST Array

I have an Array called nodeValues which contains a nested set of attributes for each product.  I need some help to identify only the unique set of attributes from this array.  This array contains a nested table for every product like this:

This table look like this:
    [0] nodeurl = Product 123
           Value
                       [0] Attributetitle = Price
                       [1] Attributetitle = Description
                      [2] Attributetitle = Weight
    [1] nodeurl = Product 888
           Value
                       [0] Attributetitle = Price
                       [1] Attributetitle = Description
                      [2] Attributetitle = Weight
   [2] nodeurl = Product 999
        ..............

All I want to is create a unique set of attributes from the nodeurl array.   For example;

                       [0] Attributetitle = Price
                       [1] Attributetitle = Description
                       [2] Attributetitle = Weight

Here is how I started to code for this:

 foreach (var items in nodeValues)
                  {
                      var Filtervalue = items.value.Select(item => item).Distinct().ToArray();
                      foreach (var attributes in Filtervalue)
                      {
                          FilteredAttributes.Add(....)   ---> How can I not add a duplicate attribute row?   Is there a way to prevent from adding the same attribute to this list array or perhaps a better way I get just get the unique attributes from this array without a forloop?
                      }
                  }

Below is the nodevalue class:

public partial class nodeValue : object, System.ComponentModel.INotifyPropertyChanged {
       
        private string nodeURLField;
       
        private value[] valueField;

Below are the list arrays.

List<FilteredValuesOfAttribure> FilteredValueOfProduct = new List<FilteredValuesOfAttribure>();
List<FilteredValuesOfAttribure> FilteredAttributes = new List<FilteredValuesOfAttribure>();

Below is the class:

public class FilteredValuesOfAttribure
    {
        public string attributeURL { get; set; }
        public string attributeTtitle { get; set; }
        public string value1 { get; set; }
        public string id { get; set; }
        public string name { get; set; }
    }