How to use LINQ Distinct() with multiple fields

Question

I have the following EF class derived from a database (simplified)

class Product
{ 
     public string ProductId;
     public string Product         


        

Answer 1

the solution to your problem looks like this:

public class Category {
  public long CategoryId { get; set; }
  public string CategoryName { get; set; }
} 

...

public class CategoryEqualityComparer : IEqualityComparer
{
   public bool Equals(Category x, Category y)
     => x.CategoryId.Equals(y.CategoryId)
          && x.CategoryName .Equals(y.CategoryName, 
 StringComparison.OrdinalIgnoreCase);

   public int GetHashCode(Mapping obj)
     => obj == null 
         ? 0
         : obj.CategoryId.GetHashCode()
           ^ obj.CategoryName.GetHashCode();
}

...

 var distinctCategories = product
     .Select(_ => 
        new Category {
           CategoryId = _.CategoryId, 
           CategoryName = _.CategoryName
        })
     .Distinct(new CategoryEqualityComparer())
     .ToList();