Removed field/column name checking of input type in TextLoader. (#327)

Author: zeahmed

src/Microsoft.ML/Data/TextLoader.cs

@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+using Microsoft.CSharp;
 using Microsoft.ML.Runtime;
 using Microsoft.ML.Runtime.Api;
 using Microsoft.ML.Runtime.Data;
@@ -84,8 +85,6 @@ public TextLoader CreateFrom<TInput>(bool useHeader = false,
                         $"Valid characters are 0-9, *, - and ~");
 
                 var name = mappingAttr.Name ?? field.Name;
-                if (name.Any(c => !Char.IsLetterOrDigit(c)))
-                    throw Contracts.Except($"{name} is not alphanumeric.");
 
                 Runtime.Data.TextLoader.Range[] sources;
                 if (!Runtime.Data.TextLoader.Column.TryParseSourceEx(mappingAttr.Ordinal, out sources))

test/Microsoft.ML.Tests/TextLoaderTests.cs

@@ -32,8 +32,11 @@ public void ConstructorDoesntThrow()
             Assert.NotNull(new Data.TextLoader("fakeFile.txt").CreateFrom<Input>(useHeader: false, supportSparse: false, trimWhitespace: false));
             Assert.NotNull(new Data.TextLoader("fakeFile.txt").CreateFrom<Input>(useHeader: false, supportSparse: false));
             Assert.NotNull(new Data.TextLoader("fakeFile.txt").CreateFrom<Input>(useHeader: false, allowQuotedStrings: false));
+
+            Assert.NotNull(new Data.TextLoader("fakeFile.txt").CreateFrom<InputWithUnderscore>());
         }
 
+
         [Fact]
         public void CanSuccessfullyApplyATransform()
         {
@@ -264,6 +267,15 @@ public class Input
             public float Number1;
         }
 
+        public class InputWithUnderscore
+        {
+            [Column("0")]
+            public string String_1;
+
+            [Column("1")]
+            public float Number_1;
+        }
+
         public class ModelWithoutColumnAttribute
         {
             public string String1;