build_results can't handle when is_op is false condition.

src/TensorFlowNET.Core/Sessions/BaseSession.cs

@@ -72,7 +72,7 @@ namespace Tensorflow
             // or if the call is a partial run that specifies feeds.
             var results = _do_run(final_targets.Select(x => (Operation)(object)x).ToList(), final_fetches, feed_dict_tensor);
 
-            return fetch_handler.build_results(null, results);
+            return fetch_handler.build_results(this, results);
         }
 
         /// <summary>

src/TensorFlowNET.Core/Sessions/_ElementFetchMapper.cs

@@ -11,9 +11,9 @@ namespace Tensorflow
     public class _ElementFetchMapper<T> : _FetchMapper<T>
     {
         private List<object> _unique_fetches = new List<object>();
-        private Func<List<object>, NDArray> _contraction_fn;
+        private Func<List<object>, object> _contraction_fn;
 
-        public _ElementFetchMapper(List<T> fetches, Func<List<object>, NDArray> contraction_fn)
+        public _ElementFetchMapper(List<T> fetches, Func<List<object>, object> contraction_fn)
         {
             foreach(var fetch in fetches)
             {
@@ -32,10 +32,22 @@ namespace Tensorflow
         /// <returns></returns>
         public NDArray build_results(List<object> values)
         {
-            if (values.Count == 0)
-                return null;
-            else
-                return _contraction_fn(values);
+            NDArray result = null;
+
+            if (values.Count > 0)
+            {
+                var ret = _contraction_fn(values);
+                switch (ret)
+                {
+                    case NDArray value:
+                        result = value;
+                        break;
+                    default:
+                        break;
+                }
+            }
+
+            return result;
         }
 
         public List<object> unique_fetches()

src/TensorFlowNET.Core/Sessions/_FetchHandler.cs

@@ -16,7 +16,7 @@ namespace Tensorflow
         private List<Tensor> _final_fetches = new List<Tensor>();
         private List<T> _targets = new List<T>();
 
-        public _FetchHandler(Graph graph, T fetches, Dictionary<Tensor, NDArray> feeds = null, object feed_handles = null)
+        public _FetchHandler(Graph graph, T fetches, Dictionary<Tensor, NDArray> feeds = null, Action feed_handles = null)
         {
             _fetch_mapper = new _FetchMapper<T>().for_fetch(fetches);
             foreach(var fetch in _fetch_mapper.unique_fetches())
@@ -40,18 +40,32 @@ namespace Tensorflow
             _final_fetches = _fetches;
         }
 
-        public NDArray build_results(Session session, NDArray[] tensor_values)
+        public NDArray build_results(BaseSession session, NDArray[] tensor_values)
         {
             var full_values = new List<object>();
+            if (_final_fetches.Count != tensor_values.Length)
+                throw new InvalidOperationException("_final_fetches mismatch tensor_values");
 
+            int i = 0;
+            int j = 0;
             foreach(var is_op in _ops)
             {
                 if (is_op)
                 {
                     full_values.Add(null);
                 }
+                else
+                {
+                    var value = tensor_values[j];
+                    j += 1;
+                    full_values.Add(value);
+                }
+                i += 1;
             }
 
+            if (j != tensor_values.Length)
+                throw new InvalidOperationException("j mismatch tensor_values");
+
             return _fetch_mapper.build_results(full_values);
         }
 

src/TensorFlowNET.Core/Sessions/_FetchMapper.cs

@@ -10,7 +10,10 @@ namespace Tensorflow
         {
             var fetches = new List<T> { fetch };
 
-            return new _ElementFetchMapper<T>(fetches, null);
+            return new _ElementFetchMapper<T>(fetches, (List<object> fetched_vals) =>
+            {
+                return fetched_vals[0];
+            });
         }
     }
 }

src/TensorFlowNET.Core/Tensors/Tensor.Implicit.cs

@@ -25,10 +25,5 @@ namespace Tensorflow
         {
             return new Tensor(handle);
         }
-
-        public static implicit operator Tensor(RefVariable var)
-        {
-            return var._initial_value;
-        }
     }
 }

src/TensorFlowNET.Core/Variables/RefVariable.Implicit.cs

@@ -0,0 +1,24 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace Tensorflow
+{
+    public partial class RefVariable
+    {
+        public static implicit operator _VariableScopeStore(RefVariable variable)
+        {
+            return null;
+        }
+
+        public static implicit operator RefVariable(_VariableScopeStore store)
+        {
+            return null;
+        }
+
+        public static implicit operator Tensor(RefVariable var)
+        {
+            return var._AsTensor();
+        }
+    }
+}

src/TensorFlowNET.Core/Variables/RefVariable.Operators.cs

@@ -0,0 +1,16 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace Tensorflow
+{
+    public partial class RefVariable
+    {
+        public static Tensor operator +(RefVariable t1, int t2)
+        {
+            var tensor1 = t1._AsTensor();
+            var tensor2 = ops.convert_to_tensor(t2, tensor1.dtype, "y");
+            return gen_math_ops.add(tensor1, tensor2);
+        }
+    }
+}

src/TensorFlowNET.Core/Variables/RefVariable.cs

@@ -4,7 +4,7 @@ using System.Text;
 
 namespace Tensorflow
 {
-    public class RefVariable : VariableV1
+    public partial class RefVariable : VariableV1
     {
         public bool _in_graph_mode = true;
         public Tensor _initial_value;
@@ -106,14 +106,9 @@ namespace Tensorflow
             return _variable;
         }
 
-        public static implicit operator _VariableScopeStore(RefVariable variable)
+        public Tensor _AsTensor()
         {
-            return null;
-        }
-
-        public static implicit operator RefVariable(_VariableScopeStore store)
-        {
-            return null;
+            return _snapshot;
         }
     }
 }

src/TensorFlowNET.Core/ops.py.cs

@@ -59,7 +59,14 @@ namespace Tensorflow
             return get_default_graph();
         }
 
-        public static Tensor convert_to_tensor(object value, string name = "")
+        /// <summary>
+        /// Converts the given `value` to a `Tensor`.
+        /// </summary>
+        /// <param name="value"></param>
+        /// <param name="dtype"></param>
+        /// <param name="name"></param>
+        /// <returns></returns>
+        public static Tensor convert_to_tensor(object value, TF_DataType dtype = TF_DataType.DtInvalid, string name = "")
         {
             switch (value)
             {
@@ -67,7 +74,7 @@ namespace Tensorflow
                     return val;
                 default:
                     var nd = tensor_util.convert_to_numpy_ndarray(value);
-                    return tf.constant(nd, name);
+                    return constant_op.Constant(nd, name);
             }
         }
 

test/TensorFlowNET.UnitTest/VariableTest.cs

@@ -38,8 +38,8 @@ namespace TensorFlowNET.UnitTest
                 session.run(model);
                 for(int i = 0; i < 5; i++)
                 {
-                    // x = x + 1;
-                    var result = session.run(x);
+                    var x1 = x + 1;
+                    var result = session.run(x1);
                     print(result);
                 }
             }