How to merge a list of objects using LINQ

I have a class defined below

public class ResultClass()
{
    public HashSet<string> VerifiedResults { get;  private set; }
    public HashSet<string> UnverifiedResults { get;  private set; }
    bool IsBlocked {get; private set; }
}

If I have a list containing items for ResultClass, for eg., List<ResultClass>() , how can I combine the results into a single ResultClass object using LINQ.

Is a way to do what my code below does, but with LINQ, instead?

var finalResult = new ResultClass();
foreach(var item in listOfResultClass)
{
    finalResult.VerifiedResults.Union(item.VerifiedResults);
    finalResult.UnverifiedResults.Union(item.UnverifiedResults);
    finalResult.IsBlocked = item.IsBlocked;
}

This can be achieved using the LINQ Aggregate function, as can be seen in following example:

public class ResultClass
{
   public HashSet<string> VerifiedResults { get; set; } = new();
   public HashSet<string> UnverifiedResults { get; set; } = new();
   public bool IsBlocked { get; set; } = false;
}


internal class Program
{
   private static void Main()
   {
      var results = GetResults();

      var finalResult = results.Aggregate(new ResultClass(), (r, next) =>
      {
         r.IsBlocked = r.IsBlocked || next.IsBlocked;
         r.VerifiedResults.UnionWith(next.VerifiedResults);
         r.UnverifiedResults.UnionWith(next.UnverifiedResults);
         return r;        
       });
}

private static List<ResultClass> GetResults()
{
    return new List<ResultClass>()
    {
      new ResultClass()
      {
         VerifiedResults = new HashSet<string>{"first", "second" },
         UnverifiedResults = new HashSet<string>{"third" },
         IsBlocked = false
      },
      new ResultClass()
      {
         VerifiedResults = new HashSet<string>{"first", "fourth" },
         UnverifiedResults = new HashSet<string>{"fifth" },
         IsBlocked = true
      },
      new ResultClass()
      {
         VerifiedResults = new HashSet<string> (),
         UnverifiedResults = new HashSet<string>{"sixt", "seventh" },
         IsBlocked = false
      }
    };
  }

}

A few remarks:

• I adapted your ResultClass to remove compiler errors and to make it possible to initialize a list of them easily.

• for the 'IsBlocked property, I used the logical OR of all the individual IsBlocked properties.

• You should use UnionWith rather than Union in this case.

• It might be a good idea to think about possible conflicts where the same string occurs in different ResultClass instances, both in 'verified' and 'unverified' properties. It may be necessary to adapt the accumulator lambda expression to get the results you want.

As @iSR5 mentioned, you can use SelectMany. I am not sure how do you plan to assign the IsBlocked, but this seems to behave like your code:

var result = new ResultClass()
{
    VerifiedResults = new HashSet<string>(results.SelectMany(x => x.VerifiedResults)),
    UnverifiedResults = new HashSet<string>(results.SelectMany(x => x.UnverifiedResults)),
    IsBlocked = results.LastOrDefault().IsBlocked,
};

Also, please read @Johan Donne comments.