fix namespace issue in CSharpGenerator and some refactoring (dotnet#339)

fix namespace issue and refactoring

Author: Ivanidzo4ka

src/Microsoft.ML.Data/DataLoadSave/PartitionedPathParser.cs

@@ -76,7 +76,7 @@ public class Arguments : IPartitionedPathParserFactory
         {
             [Argument(ArgumentType.Multiple, HelpText = "Column definitions used to override the Partitioned Path Parser. Expected with the format name:type:numeric-source, e.g. col=MyFeature:R4:1",
                 ShortName = "col", SortOrder = 1)]
-            public Microsoft.ML.Runtime.Data.PartitionedFileLoader.Column[] Columns;
+            public PartitionedFileLoader.Column[] Columns;
 
             [Argument(ArgumentType.AtMostOnce, HelpText = "Data type of each column.")]
             public DataKind Type = DataKind.Text;

src/Microsoft.ML.PipelineInference/TransformInference.cs

@@ -6,7 +6,6 @@
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
-using Microsoft.ML;
 using Microsoft.ML.Runtime.CommandLine;
 using Microsoft.ML.Runtime.Data;
 using Microsoft.ML.Runtime.EntryPoints;
@@ -712,7 +711,7 @@ public override IEnumerable<SuggestedTransform> Apply(IntermediateColumn[] colum
                         {
                             Name = columnNameQuoted.ToString(),
                             Source = columnNameQuoted.ToString(),
-                            ResultType = ML.Transforms.DataKind.R4
+                            ResultType = ML.Data.DataKind.R4
                         });
                     }
 
@@ -721,7 +720,7 @@ public override IEnumerable<SuggestedTransform> Apply(IntermediateColumn[] colum
                         ch.Info("Suggested conversion to numeric for boolean features.");
                         var args = new SubComponent<IDataTransform, SignatureDataTransform>("Convert",
                             new[] { $"{columnArgument}type=R4" });
-                        var epInput = new ML.Transforms.ColumnTypeConverter { Column = epColumns.ToArray(), ResultType = ML.Transforms.DataKind.R4 };
+                        var epInput = new ML.Transforms.ColumnTypeConverter { Column = epColumns.ToArray(), ResultType = ML.Data.DataKind.R4 };
                         ColumnRoutingStructure.AnnotatedName[] columnsSource =
                             epColumns.Select(c => new ColumnRoutingStructure.AnnotatedName { IsNumeric = false, Name = c.Name }).ToArray();
                         ColumnRoutingStructure.AnnotatedName[] columnsDest =

src/Microsoft.ML/CSharpApi.cs

@@ -7,6 +7,7 @@
 using System.Linq;
 using System.Reflection;
 using Microsoft.ML.Runtime.CommandLine;
+using Microsoft.ML.Runtime.Internal.Tools;
 using Microsoft.ML.Runtime.Internal.Utilities;
 using Newtonsoft.Json.Linq;
 
@@ -67,13 +68,7 @@ public static JObject BuildAllManifests(IExceptionContext ectx, ModuleCatalog ca
                 {
                     var jField = new JObject();
                     jField[FieldNames.Name] = fieldInfo.Name;
-                    var type = fieldInfo.PropertyType;
-                    // Dive inside Optional.
-                    if (type.IsGenericType && type.GetGenericTypeDefinition() == typeof(Optional<>))
-                        type = type.GetGenericArguments()[0];
-                    // Dive inside Nullable.
-                    if (type.IsGenericType && type.GetGenericTypeDefinition() == typeof(Nullable<>))
-                        type = type.GetGenericArguments()[0];
+                    var type = CSharpGeneratorUtils.ExtractOptionalOrNullableType(fieldInfo.PropertyType);
                     // Dive inside Var.
                     if (type.IsGenericType && type.GetGenericTypeDefinition() == typeof(Var<>))
                         type = type.GetGenericArguments()[0];
@@ -308,14 +303,7 @@ private static JToken BuildTypeToken(IExceptionContext ectx, FieldInfo fieldInfo
                 jo[FieldNames.ItemType] = typeString;
                 return jo;
             }
-
-            // Dive inside Optional.
-            if (type.IsGenericType && type.GetGenericTypeDefinition() == typeof(Optional<>))
-                type = type.GetGenericArguments()[0];
-
-            // Dive inside Nullable.
-            if (type.IsGenericType && type.GetGenericTypeDefinition() == typeof(Nullable<>))
-                type = type.GetGenericArguments()[0];
+            type = CSharpGeneratorUtils.ExtractOptionalOrNullableType(type);
 
             // Dive inside Var.
             if (type.IsGenericType && type.GetGenericTypeDefinition() == typeof(Var<>))