如何使用 c# 查找递归函数采用的路径

我有一个对象，它有一个属性，允许我创建同一对象（嵌套对象）的另一个实例。我需要搜索一个列表并找出嵌套中对象的第一个出现。

一旦找到一个，我想找出找到它的确切路径。

我有以下课程

public class ReportRelationMapping : IReportRelationMapping
{
    string Name { get; set; }
    IReportRelation LocalRelation { get; set; }
    IReportRelation ForeignRelation { get; set; }
    IReportRelationMapping RelatedThrough { get; set; } // This creates and instance of itself creating a chain
}

假设我有上述类的以下列表

List<IReportRelationMapping> myList = new List<ReportRelationMapping> 
{
    new ReportRelationMapping 
    {
        Name = "A",
        LocalRelation = ..., 
        ForeignRelation = ...
        RelatedThrough = new ReportRelationMapping
        {
            Name = "B",
            LocalRelation = ..., 
            ForeignRelation = ...
            RelatedThrough = new ReportRelationMapping
            {
                Name = "C",
                LocalRelation = ..., 
                ForeignRelation = ...
                RelatedThrough = new ReportRelationMapping
                {
                    Name = "D",
                    LocalRelation = ..., 
                    ForeignRelation = ...
                    RelatedThrough = new ReportRelationMapping
                }
            }
        }
    }
    ,new ReportRelationMapping 
    {
        Name = "E",
        LocalRelation = ..., 
        ForeignRelation = ...
        RelatedThrough = new ReportRelationMapping
        {
            Name = "F",
            LocalRelation = ..., 
            ForeignRelation = ...
        }
    }
    ,new ReportRelationMapping 
    {
        Name = "G",
        LocalRelation = ..., 
        ForeignRelation = ...
    }
}

我需要找出找到第一个"C"所需的确切路径。我需要获取以下列表

List<ReportRelationMapping> pathToTarget = new List<ReportRelationMapping> 
{
    new ReportRelationMapping 
    {
        Name = "A",
        LocalRelation = ..., 
        ForeignRelation = ...
    }
    ,new ReportRelationMapping 
    {
        Name = "B",
        LocalRelation = ..., 
        ForeignRelation = ...
    }
    ,new ReportRelationMapping 
    {
        Name = "C",
        LocalRelation = ..., 
        ForeignRelation = ...
    }
}

我编写了一个递归方法，可以正确找到"C"，但它没有正确捕获它所采用的路径。这是我所做的

private void GetAvailableRelation(List<IReportRelationMapping> relationsMappings, string belongsTo, ref List<IReportRelationMapping> pathToTarget)
{
    var requiredRelation = relationsMappings.Where(x => x.LocalRelation.TableAlias == belongsTo || x.ForeignRelation.TableAlias == belongsTo).FirstOrDefault();
    if (requiredRelation == null)
    {
        //At this point we know there is no match on the top level, lets check the nested level
        var relatedRelations = new List<IReportRelationMapping>();
        foreach (var relationsMapping in relationsMappings)
        {
            if (relationsMapping.RelatedThrough != null)
            {
                relatedRelations.Add(relationsMapping.RelatedThrough);
            }
        }
        if (relatedRelations.Any())
        {
            GetAvailableRelation(relatedRelations, belongsTo, ref pathToTarget);
        }
        else
        {
            // Since we reached the last node and count not find a matching, reset the pathToTarget list
            pathToTarget.Clear();
        }
    }
    if (requiredRelation != null)
    {
        //Check if relation exists before adding it.
        pathToTarget.Add(requiredRelation);
    }
}

The problem seems to be that after I call the method `GetAvailableRelation` recursively, the value of `requiredRelation` will become `null` when the last line come there is nothing to add to my `pathToTarget`. 

问：如何正确生成pathToTarget列表？

    private List<IReportRelationMapping> GetAvailableRelation(List<IReportRelationMapping> relationsMappings, string belongsTo)
    {
        List<IReportRelationMapping> pathToTarget = new List<IReportRelationMapping>();
        var requiredRelation = relationsMappings.Where(x => x.LocalRelation.TableAlias == belongsTo || x.ForeignRelation.TableAlias == belongsTo).FirstOrDefault();
        if (requiredRelation != null)
        {
            //Handle the top level
            pathToTarget.Add(requiredRelation);
        } else {
            //At this point we know there is no match on the top level, lets check the nested level
            var relatedRelations = new List<IReportRelationMapping>();
            foreach (var relationsMapping in relationsMappings)
            {
                if (relationsMapping.RelatedThrough != null)
                {
                    //Add the path in between previous and next
                    pathToTarget.Add(relationsMapping);
                    foreach (var subRelation in relationsMapping.RelatedThrough)
                    {
                        relatedRelations.Add(subRelation);
                    }
                }
            }
            if (relatedRelations.Any())
            {
                //Now we know there is at least one more nested level that we need to check
                var subPathsToTarget = GetAvailableRelation(relatedRelations, belongsTo);
              if (subPathsToTarget.Any())
                {
                    //prepend the current items to the path
                    pathToTarget = pathToTarget.Concat(subPathsToTarget).ToList();
                }
                else
                {
                    //At this point we know we reach the final node and the item was not found.
                    pathToTarget.Clear();
                }
            }
        }
        return pathToTarget;
    }

public class ReportRelationMapping : IReportRelationMapping
{
    public string Name { get; set; }
    public SqlJoinStatement JoinType { get; set; }
    public IReportRelation LocalRelation { get; set; }
    public IReportRelation ForeignRelation { get; set; }
    public List<IReportRelationMapping> RelatedThrough { get; set; }
}