Ensure the named model is loaded

src/Microsoft.Extensions.ML/PredictionEnginePool.cs

@@ -50,6 +50,11 @@ public PredictionEnginePool(IServiceProvider serviceProvider,
         /// </param>
         public ITransformer GetModel(string modelName)
         {
+            if (!_namedPools.ContainsKey(modelName))
+            {
+                AddPool(modelName);
+            }
+
             return _namedPools[modelName].Loader.GetModel();
         }
 
@@ -95,14 +100,20 @@ public PredictionEngine<TData, TPrediction> GetPredictionEngine(string modelName
                     throw new ArgumentException("You need to configure a default, not named, model before you use this method.");
                 }
 
-               return _defaultEnginePool.PredictionEnginePool.Get();
+                return _defaultEnginePool.PredictionEnginePool.Get();
             }
 
+            var pool = AddPool(modelName);
+            return pool.PredictionEnginePool.Get();
+        }
+
+        private PoolLoader<TData, TPrediction> AddPool(string modelName)
+        {
             //Here we are in the world of named models where the model hasn't been built yet.
             var options = _predictionEngineOptions.Create(modelName);
             var pool = new PoolLoader<TData, TPrediction>(_serviceProvider, options);
             pool = _namedPools.GetOrAdd(modelName, pool);
-            return pool.PredictionEnginePool.Get();
+            return pool;
         }
 
         /// <summary>

test/Microsoft.Extensions.ML.Tests/PredictionEnginePoolTests.cs

@@ -0,0 +1,61 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.IO;
+using System.Threading;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Logging;
+using Microsoft.Extensions.Options;
+using Microsoft.Extensions.Primitives;
+using Microsoft.ML.Data;
+using Microsoft.ML.TestFramework;
+using Microsoft.ML.TestFrameworkCommon;
+using Xunit;
+using Xunit.Abstractions;
+
+namespace Microsoft.Extensions.ML
+{
+    public class PredictionEnginePoolTests : BaseTestClass
+    {
+        public PredictionEnginePoolTests(ITestOutputHelper output) : base(output)
+        {
+        }
+
+        [Fact]
+        public void can_load_namedmodel()
+        {
+            var services = new ServiceCollection()
+                .AddOptions()
+                .AddLogging();
+
+            services.AddPredictionEnginePool<SentimentData, SentimentPrediction>()
+               .FromFile(modelName: "model1", filePath: Path.Combine("TestModels", "SentimentModel.zip"), watchForChanges: false);
+
+            var sp = services.BuildServiceProvider();
+
+            var pool = sp.GetRequiredService<PredictionEnginePool<SentimentData, SentimentPrediction>>();
+            var model = pool.GetModel("model1");
+
+            Assert.NotNull(model);
+        }
+
+        public class SentimentData
+        {
+            [ColumnName("Label"), LoadColumn(0)]
+            public bool Sentiment;
+
+            [LoadColumn(1)]
+            public string SentimentText;
+        }
+
+        public class SentimentPrediction
+        {
+            [ColumnName("PredictedLabel")]
+            public bool Sentiment;
+
+            public float Score;
+        }
+    }
+}