Support DisposableNamedOnnxValue inputs in c# Run()

csharp/src/Microsoft.ML.OnnxRuntime/InferenceSession.cs

@@ -140,6 +140,13 @@ public IDisposableReadOnlyCollection<DisposableNamedOnnxValue> Run(IReadOnlyColl
             int inputIndex = 0;
             foreach (var input in inputs)
             {
+                // guard against accidental DisposableNamedOnnxValue inputs flowing through
+                // as the code is not equipped to handle that
+                if (input is DisposableNamedOnnxValue)
+                {
+                    throw new NotSupportedException("Input of type 'DisposableNamedOnnxValue' is not supported");
+                }
+
                 inputNames[inputIndex] = input.Name;
 
                 // create Tensor from the input if feasible, else throw notsupported exception for now

csharp/test/Microsoft.ML.OnnxRuntime.Tests/InferenceTest.cs

@@ -731,6 +731,40 @@ private void TestModelInputBOOL()
             }
         }
 
+        [Fact]
+        private void TestReusingRunOutput()
+        {
+            // model takes 1x5 input of fixed type, echoes back
+            string modelPath = Path.Combine(Directory.GetCurrentDirectory(), "test_types_BOOL.pb");
+            using (var session = new InferenceSession(modelPath))
+            {
+                var container = new List<NamedOnnxValue>();
+                var tensorIn = new DenseTensor<bool>(new bool[] { true, false, true, false, true }, new int[] { 1, 5 });
+                var nov = NamedOnnxValue.CreateFromTensor("input", tensorIn);
+                container.Add(nov);
+                var res = session.Run(container);
+
+                bool succeeded = false;
+
+                try
+                {
+                    // We feed in the output of one Run() as the input to another Run()
+                    // This causes problems as Run() tries to pin underlying managed memory of
+                    // DisposableNamedOnnxValue.
+                    // Run() should fail with a user friendly error message.
+                    session.Run(res);
+                }
+
+                catch(System.NotSupportedException e)
+                {
+                    Assert.True(e.Message.Contains("Input of type 'DisposableNamedOnnxValue' is not supported"));
+                    succeeded = true;
+                }
+
+                Assert.True(succeeded);
+            }
+        }
+
         [Fact]
         private void TestModelInputINT32()
         {