AMEEClient.MaterialMapper.MaterialMapper.EnsureMaterialMapLoaded C# (CSharp) Method

        private void EnsureMaterialMapLoaded()
        {
            if (_materialMap == null)
            {
                _materialMap = new Dictionary<string, MaterialDataItem>();

                var doc = new XmlDocument();
                var reader = new XmlTextReader(_mapFilePath);
                doc.Load(reader);
                var materials = doc.SelectNodes("//Material");
                foreach (XmlNode material in materials)
                {
                    var materialName = material.SelectNodes("MaterialName").Item(0).InnerText;
                    var densityKgPerM3 = Convert.ToDouble(material.SelectNodes("AMEE/Density").Item(0).InnerText);
                    var materialDrillDown = new List<List<string>>();
                    var drills = material.SelectNodes("AMEE/Drills/Drill");
                    foreach (XmlNode drill in drills)
                    {
                        materialDrillDown.Add(new List<string> {drill.Attributes["name"].Value, drill.InnerText});
                    }
                    var path = material.SelectNodes("AMEE/Path").Item(0).InnerText;
                    var materialDataItem = new MaterialDataItem(_ameeClient, materialName, densityKgPerM3, path, materialDrillDown);

                    _materialMap.Add(materialName, materialDataItem);
                }

            }
        }