tf.train.import_meta_graph can import CondContext.

src/TensorFlowNET.Core/Framework/meta_graph.py.cs

@@ -4,6 +4,7 @@ using System.Collections.Generic;
 using System.IO;
 using System.Linq;
 using System.Text;
+using Tensorflow.Operations;
 using static Tensorflow.CollectionDef;
 using static Tensorflow.MetaGraphDef.Types;
 
@@ -95,15 +96,29 @@ namespace Tensorflow
                         }
                         else
                         {
-                            throw new NotImplementedException("import_scoped_meta_graph_with_return_elements");
+                            foreach(var value in col.Value.BytesList.Value)
+                            {
+                                switch (col.Key)
+                                {
+                                    case "cond_context":
+                                        var proto = CondContextDef.Parser.ParseFrom(value);
+                                        var condContext = new CondContext().from_proto(proto, import_scope);
+                                        graph.add_to_collection(col.Key, condContext);
+                                        break;
+                                    default:
+                                        throw new NotImplementedException("import_scoped_meta_graph_with_return_elements");
+                                }
+                            }
                         }
                         
                         break;
+                    default:
+                        throw new NotImplementedException("import_scoped_meta_graph_with_return_elements");
                 }
             }
 
-            var variables = graph.get_collection(ops.GraphKeys.GLOBAL_VARIABLES,
-                                     scope: scope_to_prepend_to_names) as List<RefVariable>;
+            var variables = graph.get_collection<RefVariable>(ops.GraphKeys.GLOBAL_VARIABLES,
+                                     scope: scope_to_prepend_to_names);
             var var_list = new Dictionary<string, RefVariable>();
             variables.ForEach(v => var_list[ops.strip_name_scope(v.name, scope_to_prepend_to_names)] = v);
 

src/TensorFlowNET.Core/Graphs/Graph.cs

@@ -412,6 +412,11 @@ namespace Tensorflow
             return _collections.ContainsKey(name) ? _collections[name] : null;
         }
 
+        public List<T> get_collection<T>(string name, string scope = null)
+        {
+            return _collections.ContainsKey(name) ? _collections[name] as List<T> : new List<T>();
+        }
+
         public object get_collection_ref(string name)
         {
             if (!_collections.ContainsKey(name))

src/TensorFlowNET.Core/Operations/ControlFlows/CondContext.cs

@@ -8,7 +8,7 @@ namespace Tensorflow.Operations
     /// <summary>
     /// The context for the conditional construct.
     /// </summary>
-    public class CondContext : ControlFlowContext
+    public class CondContext : ControlFlowContext, IProtoBuf<CondContextDef, CondContext>
     {
 
 
@@ -35,16 +35,20 @@ namespace Tensorflow.Operations
         /// <param name="name">Name of the `CondContext` python object.</param>
         /// <param name="context_def"></param>
         /// <param name="import_scope"></param>
-        public CondContext(Tensor pred,
-            Tensor pivot,
-            int branch,
+        public CondContext(Tensor pred = null,
+            Tensor pivot = null,
+            int? branch = null,
             string name = "cond_text",
-            object context_def = null,
+            CondContextDef context_def = null,
             string import_scope = null)
         {
+            if (pred == null && context_def == null) return;
+
             _name = ops.get_default_graph().unique_name(name);
-            if (context_def != null)
-                throw new NotImplementedException("CondContext context_def is not null");
+            if (context_def != null)
+            {
+                _init_from_proto(context_def, import_scope: import_scope);
+            }
             else
             {
                 // Initializes the default fields.
@@ -61,6 +65,18 @@ namespace Tensorflow.Operations
             }
         }
 
+        private void _init_from_proto(CondContextDef context_def, string import_scope = null)
+        {
+            var g = ops.get_default_graph();
+            _name = ops.prepend_name_scope(context_def.ContextName, import_scope);
+            var p1 = ops.prepend_name_scope(context_def.PredName, import_scope);
+            _pred = g.as_graph_element(p1) as Tensor;
+            var p2 = ops.prepend_name_scope(context_def.PivotName, import_scope);
+            _pivot = g.as_graph_element(p2) as Tensor;
+            _branch = context_def.Branch;
+            __init__(values_def: context_def.ValuesDef, import_scope: import_scope);
+        }
+
         /// <summary>
         /// Add `val` to the current context and its outer context recursively.
         /// </summary>
@@ -230,6 +246,22 @@ namespace Tensorflow.Operations
         public override void  AddInnerOp(Operation resultOp)
         {
             throw new NotImplementedException();
-        }
+        }
+
+        public CondContextDef to_proto(string export_scope)
+        {
+            throw new NotImplementedException();
+        }
+
+        public CondContext from_proto(CondContextDef proto, string import_scope)
+        {
+            var ret = new CondContext(context_def: proto, import_scope: import_scope);
+
+            ret.Enter();
+            foreach (var nested_def in proto.NestedContexts)
+                throw new NotImplementedException("");
+            ret.Exit();
+            return ret;
+        }
     }
 }

src/TensorFlowNET.Core/Operations/ControlFlows/ControlFlowContext.cs

@@ -32,6 +32,8 @@ namespace Tensorflow.Operations
         protected Stack<IControlFlowContext> _context_stack;
         protected IControlFlowContext _outer_context;
 
+        protected Dictionary<string, ITensorOrOperation> _external_values;
+
         public ControlFlowContext()
         {
             _context_stack = new Stack<IControlFlowContext>();
@@ -40,15 +42,43 @@ namespace Tensorflow.Operations
         public string name { get => _name; }
         protected string _name;
 
-        public void __init__()
+        public void __init__(ValuesDef values_def = null, string import_scope = null)
         {
-
+            _outer_context = ops.get_default_graph()._get_control_flow_context();
+            if (values_def != null)
+                _init_values_from_proto(values_def, import_scope: import_scope);
         }
 
         public void __enter__()
         {
         }
 
+        /// <summary>
+        /// Initializes values and external_values from `ValuesDef` protocol buffer.
+        /// </summary>
+        /// <param name="values_def"></param>
+        /// <param name="import_scope"></param>
+        protected void _init_values_from_proto(ValuesDef values_def, string import_scope = null)
+        {
+            _external_values = new Dictionary<string, ITensorOrOperation>();
+            foreach (var value in values_def.Values)
+                _values.Add(value);
+            var g = ops.get_default_graph();
+            foreach(var value in values_def.ExternalValues)
+            {
+                var k = ops.prepend_name_scope(value.Key, import_scope);
+                var v = value.Value;
+                _external_values[k] = g.as_graph_element(ops.prepend_name_scope(v, import_scope));
+            }
+
+            var op_names = _values.Where(x => !_external_values.ContainsKey(x))
+                .Select(x => x.Split(':')[0])
+                .ToArray();
+
+            foreach (var op in op_names)
+                (g.as_graph_element(op) as Operation)._set_control_flow_context(this);
+        }
+
         public void __exit__()
         {
         }

src/TensorFlowNET.Core/Operations/Operation.cs

@@ -287,7 +287,7 @@ namespace Tensorflow
             // Reset cached inputs.
             _inputs = null;// new InputList(new Tensor[] { tensor }); // is this right? original code: self._inputs_val=None
             // TODO: implement below code dependencies
-            // c_api.TF_UpdateEdge(graph, output, input, status);
+            c_api.TF_UpdateEdge(graph, output, input, status);
         }
 
         private void _assert_same_graph(Tensor tensor)

src/TensorFlowNET.Core/Operations/control_flow_ops.py.cs

@@ -330,7 +330,7 @@ namespace Tensorflow
                     tensor.op.graph.prevent_fetching(tensor.op);
 
                 // Build the graph for the true branch in a new context.
-                var context_t = new CondContext(pred, pivot_1, branch: 1);
+                var context_t = new CondContext(pred: pred, pivot: pivot_1, branch: 1);
                 ITensorOrOperation orig_res_t;
                 Tensor res_t;
                 try
@@ -343,7 +343,7 @@ namespace Tensorflow
                     context_t.Exit();
                 }
                 // Build the graph for the false branch in a new context.
-                var context_f = new CondContext(pred, pivot_2, branch: 0);
+                var context_f = new CondContext(pred: pred, pivot: pivot_2, branch: 0);
                 ITensorOrOperation orig_res_f;
                 Tensor res_f;
                 try
@@ -411,13 +411,13 @@ namespace Tensorflow
                     tensor.op.graph.prevent_fetching(tensor.op);
 
                 // Build the graph for the true branch in a new context.
-                var context_t = new CondContext(pred, pivot_1, branch: 1);
+                var context_t = new CondContext(pred: pred, pivot: pivot_1, branch: 1);
                 context_t.Enter();
                 var (orig_res_t, res_t) = context_t.BuildCondBranch(true_fn);
                 context_t.Exit();
 
                 // Build the graph for the false branch in a new context.
-                var context_f = new CondContext(pred, pivot_2, branch: 0);
+                var context_f = new CondContext(pred: pred, pivot: pivot_2, branch: 0);
                 context_f.Enter();
                 var (orig_res_f, res_f) = context_f.BuildCondBranch(false_fn);
                 context_f.Exit();

src/TensorFlowNET.Core/Protobuf/IProtoBuf.cs

@@ -8,7 +8,7 @@ namespace Tensorflow
     /// In order for a object to be serialized to and from MetaGraphDef, 
     /// the class must implement to_proto() and from_proto() methods
     /// </summary>
-    public interface IProtoBuf
+    public interface IProtoBuf<TProtoDef, TDef>
     {
         string name { get; }
 
@@ -17,15 +17,15 @@ namespace Tensorflow
         /// </summary>
         /// <param name="export_scope"></param>
         /// <returns></returns>
-        VariableDef to_proto(string export_scope);
+        TProtoDef to_proto(string export_scope);
 
         /// <summary>
         /// Returns a `Variable` object created from `variable_def`.
         /// </summary>
         /// <typeparam name="T"></typeparam>
-        /// <param name="variable_def"></param>
+        /// <param name="proto"></param>
         /// <param name="import_scope"></param>
         /// <returns></returns>
-        T from_proto<T>(VariableDef variable_def, string import_scope);
+        TDef from_proto(TProtoDef proto, string import_scope);
     }
 }

src/TensorFlowNET.Core/Protobuf/README.md

@@ -1,10 +1,12 @@
 ### Download compiler from https://github.com/protocolbuffers/protobuf/releases
+Work in command line
+
 ```shell
+cd tensorflow
+
 set SRC_DIR=D:/Projects/tensorflow
 set DST_DIR=D:/Projects/TensorFlow.NET/src/TensorFlowNET.Core/Protobuf
 
-cd tensorflow
-
 protoc -I=%SRC_DIR% --csharp_out=%DST_DIR% tensorflow/core/framework/resource_handle.proto
 protoc -I=%SRC_DIR% --csharp_out=%DST_DIR% tensorflow/core/framework/tensor_shape.proto
 protoc -I=%SRC_DIR% --csharp_out=%DST_DIR% tensorflow/core/framework/types.proto
@@ -32,6 +34,7 @@ protoc -I=%SRC_DIR% --csharp_out=%DST_DIR% tensorflow/core/protobuf/cluster.prot
 protoc -I=%SRC_DIR% --csharp_out=%DST_DIR% tensorflow/core/protobuf/config.proto
 protoc -I=%SRC_DIR% --csharp_out=%DST_DIR% tensorflow/core/protobuf/debug.proto
 protoc -I=%SRC_DIR% --csharp_out=%DST_DIR% tensorflow/core/protobuf/rewriter_config.proto
+protoc -I=%SRC_DIR% --csharp_out=%DST_DIR% tensorflow/core/protobuf/control_flow.proto
 protoc -I=%SRC_DIR% --csharp_out=%DST_DIR% tensorflow/python/training/checkpoint_state.proto
 ```
 

src/TensorFlowNET.Core/Variables/RefVariable.cs

@@ -7,7 +7,7 @@ using System.Text;
 
 namespace Tensorflow
 {
-    public partial class RefVariable : VariableV1, IProtoBuf
+    public partial class RefVariable : VariableV1, IProtoBuf<VariableDef, RefVariable>
     {
         public bool _in_graph_mode = true;
         public Tensor _initial_value;
@@ -288,7 +288,7 @@ namespace Tensorflow
             throw new NotImplementedException("to_proto RefVariable");
         }
 
-        public T from_proto<T>(VariableDef variable_def, string import_scope)
+        public RefVariable from_proto(VariableDef proto, string import_scope)
         {
             throw new NotImplementedException();
         }

src/TensorFlowNET.Core/ops.py.cs

@@ -376,7 +376,7 @@ namespace Tensorflow
                 if (import_scope.EndsWith("/"))
                     import_scope = import_scope.Substring(0, import_scope.Length - 1);
 
-                throw new NotImplementedException("prepend_name_scope");
+                return $"{import_scope}/{name}";
             }
             else
                 return name;

test/TensorFlowNET.UnitTest/control_flow_ops_test/CondTestCases.cs

@@ -10,17 +10,28 @@ namespace TensorFlowNET.UnitTest.control_flow_ops_test
     [TestClass]
     public class CondTestCases : PythonTest
     {
-
         [TestMethod]
         public void testCondTrue()
         {
-            with(tf.Session(), sess =>
+            var graph = tf.Graph().as_default();
+
+            with(tf.Session(graph), sess =>
             {
                 var x = tf.constant(2);
                 var y = tf.constant(5);
-                var z = control_flow_ops.cond(tf.less(x, y),
-                    () => tf.multiply(x, 17),
-                    () => tf.add(y, 23));
+                var pred = tf.less(x, y);
+
+                Func<ITensorOrOperation> if_true = delegate
+                {
+                    return tf.multiply(x, 17);
+                };
+
+                Func<ITensorOrOperation> if_false = delegate
+                {
+                    return tf.add(y, 23);
+                };
+
+                var z = control_flow_ops.cond(pred, if_true, if_false);
                 int result = z.eval(sess);
                 assertEquals(result, 34);
             });