C# Flaten a nested list to list of different object for display in a datagrid

Question

I'm having an issue presenting my nested collection in a WPF Datagrid. bellow is the code that is giving me the desired result, but I wonder if it is possible to make it simpler?

public async Task LoadRecepi(short id)
    {
        Recepi = await _recepiDataService.Get(id);

        var flat = new List<FlatRecepi1>();
        foreach (var step in Recepi.Step)
        {
            flat.Add(new FlatRecepi1 { 
                RecepiId = step.RecepiId,
                StepId = step.SPTagId,
                Activity = step.Activity,
                PVTagName = step.PVTag.Name
            });  
            foreach (var node in step.Nodes)
            {
                flat.Add(new FlatRecepi1
                {
                    StepId = node.SPTagId,
                    SPTagName = node.SPTag.Name,
                    PVTagName = node.PVTag.Name
                });
            }
        }           

    }

thankyou so much for your help.

public class FlatRecepi1
{        
    public short RecepiId { get; set; }
    public short StepId { get; set; }
    public Activity Activity { get; set; }
    public short NodeId { get; set; }
    public string StepName { get; set; }
    public string PVTagName { get; set; }
    public string SPTagName { get; set; }
    public Operator Operator { get; set; }

}

Answer 1

You can use a combination of Enumerable.SelectMany and Enumerable.Prepend.

The following code will project out each step's nodes into a collection of FlatRecepi1 and then prepend the FlatRecepi1 corresponding to the step at the start of the collection. Finally, the SelectMany flattens this "collection of collections" into a single list. This should give you the same ordering as the current code.

var flat = Recepi.Step.SelectMany(step => 
   step.Nodes.Select(node => new FlatRecepi1 { 
       StepId = node.SPTagId, 
       SPTagName = node.SPTag.Name,
       PVTagName = node.PVTag.Name 
   }).Prepend(new FlatRecepi1 { 
       RecepiId = step.RecepiId,
       StepId = step.SPTagId,
       Activity = step.Activity,
       PVTagName = step.PVTag.Name,
   })
).ToList();

If Prepend is not available to you because you are using an older framework, we can achieve the same with Enumerable.Concat:

var flat = Recepi.Step.SelectMany(step => 
   new [] { 
      new FlatRecepi1 { 
        RecepiId = step.RecepiId,
        StepId = step.SPTagId,
        Activity = step.Activity,
        PVTagName = step.PVTag.Name,
      }
   }.Concat(
      step.Nodes.Select(node => new FlatRecepi1 { 
        StepId = node.SPTagId, 
        SPTagName = node.SPTag.Name,
        PVTagName = node.PVTag.Name 
      }) 
   )
).ToList();