upd

ZeroLevel.SQL/Contracts/IDbProvider.cs

@@ -21,8 +21,5 @@ namespace ZeroLevel.SqlServer
         void LazySelect(string query, DbParameter[] par, Func<DbDataReader, bool> readHandler);
         void LazySelect(string query, DbParameter[] par, Func<DbDataReader, bool> readHandler, int timeout);
         void LazySelectWithParameters(string query, IEnumerable<KeyValuePair<string, object>> par, Func<DbDataReader, bool> readHandler, int timeout);
-
-        T Read<T>(DbDataReader reader, int index);
-        T Read<T>(DbDataReader reader, string name);
     }
 }

ZeroLevel.SQL/DBReader.cs

@@ -0,0 +1,29 @@
+using System;
+using System.Data.Common;
+
+namespace ZeroLevel.SqlServer
+{
+    public static class DBReader
+    {
+        public static T Read<T>(this DbDataReader reader, int index)
+        {
+            if (reader[index] == DBNull.Value) return default(T);
+            Type t;
+            if ((t = Nullable.GetUnderlyingType(typeof(T))) != null)
+            {
+                return (T)Convert.ChangeType(reader[index], t);
+            }
+            return (T)Convert.ChangeType(reader[index], typeof(T));
+        }
+        public static T Read<T>(this DbDataReader reader, string name)
+        {
+            if (reader[name] == DBNull.Value) return default(T);
+            Type t;
+            if ((t = Nullable.GetUnderlyingType(typeof(T))) != null)
+            {
+                return (T)Convert.ChangeType(reader[name], t);
+            }
+            return (T)Convert.ChangeType(reader[name], typeof(T));
+        }
+    }
+}

ZeroLevel.SQL/SqlDbProvider.cs

@@ -471,16 +471,5 @@ namespace ZeroLevel.SqlServer
             }
         }
         #endregion
-
-        public T Read<T>(DbDataReader reader, int index)
-        {
-            if (reader[index] == DBNull.Value) return default(T);
-            return (T)Convert.ChangeType(reader[index], typeof(T));
-        }
-        public T Read<T>(DbDataReader reader, string name)
-        {
-            if (reader[name] == DBNull.Value) return default(T);
-            return (T)Convert.ChangeType(reader[name], typeof(T));
-        }
     }
 }

ZeroLevel.SQL/ZeroLevel.SQL.csproj

@@ -2,6 +2,7 @@
 
   <PropertyGroup>
     <TargetFramework>netstandard2.0</TargetFramework>
+    <Platforms>AnyCPU;x64</Platforms>
   </PropertyGroup>
 
   <ItemGroup>

ZeroLevel/Services/Trees/Generic.cs

@@ -52,5 +52,25 @@ namespace ZeroLevel.Services.Trees
                 }
             }
         }
+
+        /// <summary>
+        /// traversing a tree in width from left to right
+        /// </summary>
+        public IEnumerable<GNode<T>> Plain()
+        {
+            var queue = new Queue<GNode<T>>();
+            foreach (var r in _rootNodes) {
+                queue.Enqueue(r.Value);
+            }
+            while (queue.Count > 0)
+            {
+                var current = queue.Dequeue();
+                yield return current;
+                foreach (var r in current.Nodes)
+                {
+                    queue.Enqueue(r.Value);
+                }
+            }
+        }
     }
 }