@@ -14,6 +14,8 @@ namespace Tensorflow.Keras.Layers
     /// A layer is a class implementing common neural networks operations, such
     /// as convolution, batch norm, etc. These operations require managing weights,
     /// losses, updates, and inter-layer connectivity.
+    /// 
+    /// tensorflow\python\keras\engine\base_layer.py
     /// </summary>
     public class Layer : AutoTrackable
     {
@@ -55,9 +57,14 @@ public Layer(bool trainable = true,
         {
             this.trainable = trainable;
             this._dtype = dtype;
+            // A stateful layer is a layer whose updates are run during inference too,
+            // for instance stateful RNNs.
             stateful = false;
+            // Indicates whether `build` needs to be called upon layer call, to create
+            // the layer's weights.
             built = false;
             this.supports_masking = false;
+
             _init_set_name(name);
             _trainable_weights = new List<RefVariable>();
             _compute_previous_mask = false;
@@ -154,7 +161,8 @@ protected void _maybe_build(Tensor input)
             if (_dtype == TF_DataType.DtInvalid)
                 _dtype = input.dtype;
 
-            build(input.GetShape());
+            var input_shapes = input.GetShape();
+            build(input_shapes);
             built = true;
         }
 
 
@@ -22,8 +22,13 @@ public Layer(bool trainable = true,
             TF_DataType dtype = TF_DataType.DtInvalid,
             bool? _reuse = null) : base(trainable: trainable, name: name, dtype: dtype)
         {
+            // For backwards compatibility, legacy layers do not use `ResourceVariable`
+            // by default.
             this._use_resource_variables = false;
             this._reuse = _reuse;
+
+            // Avoid an incorrect lint error
+            _trainable_weights = new List<RefVariable>();
             this.built = false;
             _keras_style = false;
         }
@@ -130,13 +135,12 @@ protected virtual RefVariable add_weight(string name,
                             initializer: initializer,
                             trainable: trainable,
                             getter: (name1, shape1, dtype1, initializer1, trainable1) =>
-                            {
-                                return tf.get_variable(name1,
+                                tf.get_variable(name1,
                                     shape: new TensorShape(shape1),
                                     dtype: dtype1,
                                     initializer: initializer1,
-                                    trainable: trainable1);
-                            });
+                                    trainable: trainable1)
+                            );
 
                         //if (init_graph != null)
                             //var trainable_variables = variables.trainable_variables();
 
@@ -15,7 +15,7 @@ public partial class Tensor
         public static Tensor operator -(Tensor x, Tensor y) => BinaryOpWrapper("sub", x, y);
         public static Tensor operator -(Tensor x, int y) => BinaryOpWrapper("sub", x, y);
         public static Tensor operator -(Tensor x, double y) => BinaryOpWrapper("sub", x, y);
-        public static Tensor operator -(float x, Tensor y) => BinaryOpWrapper("Sub", x, y);
+        public static Tensor operator -(float x, Tensor y) => BinaryOpWrapper("sub", x, y);
 
         public static Tensor operator *(float x, Tensor y) => BinaryOpWrapper("mul", x, y);
         public static Tensor operator *(double x, Tensor y) => BinaryOpWrapper("mul", x, y);
 
@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Linq;
 using System.Text;
 
 namespace Tensorflow
@@ -16,7 +17,8 @@ public class PureVariableScope : IPython
         private _VariableScopeStore _var_scope_store;
         private VariableScope variable_scope_object;
         private VariableScope _cached_variable_scope_object;
-
+        VariableScope _last_variable_scope_object;
+        Dictionary<string, int> _old_subscopes;
         public PureVariableScope(string name, 
             string old_name_scope = null, 
             TF_DataType dtype = TF_DataType.DtInvalid)
@@ -51,6 +53,7 @@ public void __enter__()
             if(_scope != null)
             {
                 _var_scope_store.open_variable_scope(_new_name);
+                _old_subscopes = _var_scope_store.variable_scopes_count.ToDictionary(kv => kv.Key, kv => kv.Value);
                 variable_scope_object = _cached_variable_scope_object;
             }
             else
@@ -66,6 +69,7 @@ public void __enter__()
                 _var_scope_store.open_variable_scope(_new_name);
             }
             _var_scope_store.current_scope = variable_scope_object;
+            _last_variable_scope_object = variable_scope_object;
         }
 
         public void Dispose()
@@ -75,7 +79,12 @@ public void Dispose()
 
         public void __exit__()
         {
-            
+            // If jumping out from a non-prolonged scope, restore counts.
+            if (_scope != null)
+                _var_scope_store.variable_scopes_count = _old_subscopes;
+            else
+                _var_scope_store.close_variable_subscopes(_new_name);
+            _var_scope_store.current_scope = _old;
         }
 
         public static implicit operator VariableScope(PureVariableScope scope)
 
@@ -7,7 +7,7 @@ namespace Tensorflow
     public class _VariableScopeStore
     {
         public VariableScope current_scope { get; set; }
-        private Dictionary<string, int> variable_scopes_count;
+        public Dictionary<string, int> variable_scopes_count;
 
         public _VariableScopeStore()
         {
@@ -23,6 +23,13 @@ public void open_variable_scope(string scope_name)
                 variable_scopes_count[scope_name] = 1;
         }
 
+        public void close_variable_subscopes(string scope_name)
+        {
+            foreach (var k in variable_scopes_count.Keys)
+                if (scope_name == null || k.StartsWith(scope_name + "/"))
+                    variable_scopes_count[k] = 0;
+        }
+
         public int variable_scope_count(string scope_name)
         {
             if (variable_scopes_count.ContainsKey(scope_name))
 
@@ -106,13 +106,13 @@ private VariableScope _enter_scope_uncached()
 
             if (_name != null || _scope != null)
             {
-                var name_scope = _name == null ? _scope.name.Split('/').Last() : _name;
+                var name_scope = _scope.name.Split('/').Last();
                 if (current_name_scope == null)
                     current_name_scope = ops.name_scope(name_scope);
                 current_name_scope.__enter__();
                 var current_name_scope_name = current_name_scope;
                 _current_name_scope = current_name_scope;
-                string old_name_scope = current_name_scope_name;
+                string old_name_scope = _scope.original_name_scope;
 
                 if(_scope == null)
                     pure_variable_scope = new PureVariableScope(_name, old_name_scope: old_name_scope);
@@ -139,14 +139,22 @@ private VariableScope _enter_scope_uncached()
             }
         }
 
+        /// <summary>
+        /// Get a name with the given prefix unique in the current variable scope.
+        /// </summary>
+        /// <param name="prefix"></param>
+        /// <returns></returns>
         public static string _get_unique_variable_scope(string prefix)
         {
             var var_scope_store = get_variable_scope_store();
             var current_scope = get_variable_scope();
             string name = !string.IsNullOrEmpty(current_scope.name) ? current_scope.name + "/" + prefix : prefix;
             if (var_scope_store.variable_scope_count(name) == 0)
                 return prefix;
-            throw new NotImplementedException("_get_unique_variable_scope");
+            var idx = 1;
+            while (var_scope_store.variable_scope_count($"{name}_{idx}") > 0)
+                idx += 1;
+            return $"{prefix}_{idx}";
         }
 
         public static RefVariable default_variable_creator(object initial_value,
@@ -250,6 +258,7 @@ public static implicit operator VariableScope(variable_scope scope)
 
         public void __exit__()
         {
+            _cached_pure_variable_scope.__exit__();
             if (_current_name_scope != null)
                 _current_name_scope.__exit__();
         }
Original file line number	Diff line number	Diff line change
@@ -7,7 +7,7 @@ namespace Tensorflow
7	7	public class _VariableScopeStore
8	8	{
9	9	public VariableScope current_scope { get; set; }
10		- private Dictionary<string, int> variable_scopes_count;
	10	+ public Dictionary<string, int> variable_scopes_count;
11	11
12	12	public _VariableScopeStore()
13	13	{
@@ -23,6 +23,13 @@ public void open_variable_scope(string scope_name)
23	23	variable_scopes_count[scope_name] = 1;
24	24	}
25	25
	26	+ public void close_variable_subscopes(string scope_name)
	27	+ {
	28	+ foreach (var k in variable_scopes_count.Keys)
	29	+ if (scope_name == null \|\| k.StartsWith(scope_name + "/"))
	30	+ variable_scopes_count[k] = 0;
	31	+ }
	32	+
26	33	public int variable_scope_count(string scope_name)
27	34	{
28	35	if (variable_scopes_count.ContainsKey(scope_name))