diff --git a/SaneTsv.cs b/SaneTsv.cs
index ff3b83f..71df6ea 100644
--- a/SaneTsv.cs
+++ b/SaneTsv.cs
@@ -84,7 +84,7 @@ public class SaneTsv
     }
     parsed.Records = new List<T>();
 
-    var columnTypes = new List<Type>();
+    var columnTypes = new List<ColumnType>();
     var columnNames = new List<string>();
     var columnPropertyInfos = new List<PropertyInfo>();
     int columnCount = 0;
@@ -190,46 +190,46 @@ public class SaneTsv
             columnName = columnString;
           }
 
-          Type type;
+          ColumnType type;
 
           switch (columnTypeString)
           {
             case "":
               numTypesBlank++;
-              type = typeof(StringType);
+              type = new StringType();
               break;
             case "string":
-              type = typeof(StringType);
+              type = new StringType();
               break;
             case "boolean":
-              type = typeof(BooleanType);
+              type = new BooleanType();
               break;
             case "float32":
-              type = typeof(Float32Type);
+              type = new Float32Type();
               break;
             case "float32-le":
-              type = typeof(Float32LEType);
+              type = new Float32LEType();
               break;
             case "float64":
-              type = typeof(Float64Type);
+              type = new Float64Type();
               break;
             case "float64-le":
-              type = typeof(Float64LEType);
+              type = new Float64LEType();
               break;
             case "uint32":
-              type = typeof(UInt32Type);
+              type = new UInt32Type();
               break;
             case "uint64":
-              type = typeof(UInt64Type);
+              type = new UInt64Type();
               break;
             case "int32":
-              type = typeof(Int32Type);
+              type = new Int32Type();
               break;
             case "int64":
-              type = typeof(Int64Type);
+              type = new Int64Type();
               break;
             case "binary":
-              type = typeof(BinaryType);
+              type = new BinaryType();
               break;
             default:
               throw new Exception($"Invalid type '{columnTypeString}' for column {j}");
@@ -242,7 +242,7 @@ public class SaneTsv
             throw new Exception($"Column {j} has name {columnName}, but expected {columnNames[j]}");
           }
 
-          if (columnTypes[j] != type)
+          if (columnTypes[j].GetType() != type.GetType())
           {
             throw new Exception($"Column {j} has type {type}, but expected {columnTypes[j]}");
           }
@@ -348,7 +348,7 @@ public class SaneTsv
   // startIndex is in we'd have to go back to the start of the record's comment, and to know 
   // exactly where that comment started we'd have to go back to the start of the record before that
   // (not including that other record's comment).
-  protected static T[] Parse<T>(byte[] inputBuffer, FormatType format, PropertyInfo[] columnPropertyInfos, Type[] columnTypes, int startIndex, int endIndex) where T : TsvRecord, new()
+  protected static T[] Parse<T>(byte[] inputBuffer, FormatType format, PropertyInfo[] columnPropertyInfos, ColumnType[] columnTypes, int startIndex, int endIndex) where T : TsvRecord, new()
   {
     var fieldBytes = new List<byte>();
     var fields = new List<byte[]>();
@@ -509,12 +509,12 @@ public class SaneTsv
     return parsed.ToArray();
   }
 
-  protected static T ParseCurrentCommentedRecord<T>(Type[] columnTypes, PropertyInfo[] properties, List<byte[]> fields, string comment, int line) where T : CommentedTsvRecord, new()
+  protected static T ParseCurrentCommentedRecord<T>(ColumnType[] columnTypes, PropertyInfo[] properties, List<byte[]> fields, string comment, int line) where T : CommentedTsvRecord, new()
   {
     return (T)ParseCurrentRecord<T>(columnTypes, properties, fields, comment, line);
   }
 
-  protected static T ParseCurrentRecord<T>(Type[] columnTypes, PropertyInfo[] properties, List<byte[]> fields, string comment, int line) where T : TsvRecord, new()
+  protected static T ParseCurrentRecord<T>(ColumnType[] columnTypes, PropertyInfo[] properties, List<byte[]> fields, string comment, int line) where T : TsvRecord, new()
   {
     T record = new T();
 
@@ -532,7 +532,7 @@ public class SaneTsv
     for (int j = 0; j < fields.Count; j++)
     {
       // All other types require the content to be UTF-8. Binary fields can ignore that.
-      if (columnTypes[j] == typeof(BinaryType))
+      if (columnTypes[j].GetType() == typeof(BinaryType))
       {
         // TODO: Use faster method for property setting
         // e.g. https://blog.marcgravell.com/2012/01/playing-with-your-member.html
@@ -541,7 +541,7 @@ public class SaneTsv
         properties[j].SetValue(record, fields[j]);
         continue;
       }
-      else if (columnTypes[j] == typeof(Float32LEType))
+      else if (columnTypes[j].GetType() == typeof(Float32LEType))
       {
         byte[] floatBytes;
         if (!LittleEndian)
@@ -560,7 +560,7 @@ public class SaneTsv
 
         continue;
       }
-      else if (columnTypes[j] == typeof(Float64LEType))
+      else if (columnTypes[j].GetType() == typeof(Float64LEType))
       {
         byte[] floatBytes;
         if (!LittleEndian)
@@ -592,11 +592,11 @@ public class SaneTsv
 
       // TODO: Add checking for numeric types format
 
-      if (columnTypes[j] == typeof(StringType))
+      if (columnTypes[j].GetType() == typeof(StringType))
       {
         properties[j].SetValue(record, fieldString);
       }
-      else if (columnTypes[j] == typeof(BooleanType))
+      else if (columnTypes[j].GetType() == typeof(BooleanType))
       {
         bool parsedBool;
         if (fieldString == "TRUE")
@@ -614,7 +614,7 @@ public class SaneTsv
 
         properties[j].SetValue(record, parsedBool);
       }
-      else if (columnTypes[j] == typeof(Float32Type))
+      else if (columnTypes[j].GetType() == typeof(Float32Type))
       {
         float parsedFloat;
         if (!float.TryParse(fieldString, out parsedFloat))
@@ -635,7 +635,7 @@ public class SaneTsv
 
         properties[j].SetValue(record, parsedFloat);
       }
-      else if (columnTypes[j] == typeof(Float64Type))
+      else if (columnTypes[j].GetType() == typeof(Float64Type))
       {
         double parsedDouble;
         if (!double.TryParse(fieldString, out parsedDouble))
@@ -656,7 +656,7 @@ public class SaneTsv
 
         properties[j].SetValue(record, parsedDouble);
       }
-      else if (columnTypes[j] == typeof(UInt32Type))
+      else if (columnTypes[j].GetType() == typeof(UInt32Type))
       {
         if (!UInt32.TryParse(fieldString, out UInt32 parsedUInt32))
         {
@@ -665,7 +665,7 @@ public class SaneTsv
 
         properties[j].SetValue(record, parsedUInt32);
       }
-      else if (columnTypes[j] == typeof(UInt64Type))
+      else if (columnTypes[j].GetType() == typeof(UInt64Type))
       {
         if (!UInt64.TryParse(fieldString, out UInt64 parsedUInt64))
         {
@@ -674,7 +674,7 @@ public class SaneTsv
 
         properties[j].SetValue(record, parsedUInt64);
       }
-      else if (columnTypes[j] == typeof(Int32Type))
+      else if (columnTypes[j].GetType() == typeof(Int32Type))
       {
         if (!Int32.TryParse(fieldString, out Int32 parsedInt32))
         {
@@ -683,7 +683,7 @@ public class SaneTsv
 
         properties[j].SetValue(record, parsedInt32);
       }
-      else if (columnTypes[j] == typeof(Int64Type))
+      else if (columnTypes[j].GetType() == typeof(Int64Type))
       {
         if (!Int64.TryParse(fieldString, out Int64 parsedInt64))
         {
@@ -1066,99 +1066,151 @@ public class SaneTsv
     return records.ToArray();
   }
 
-  public static Type GetColumnFromType(Type type)
+  public static ColumnType GetColumnFromString(string type)
   {
-    if (type == typeof(string))
+    if (type == "string")
     {
-      return typeof(StringType);
+      return new StringType();
     }
-    else if (type == typeof(bool))
+    else if (type == "boolean")
     {
-      return typeof(BooleanType);
+      return new BooleanType();
     }
-    else if (type == typeof(float))
+    else if (type == "float32")
     {
-      return typeof(Float32Type);
+      return new Float32Type();
     }
-    else if (type == typeof(double))
+    else if (type == "float32-le")
     {
-      return typeof(Float64Type);
+      return new Float32LEType();
     }
-    else if (type == typeof(UInt32))
+    else if (type == "float64")
     {
-      return typeof(UInt32Type);
+      return new Float64Type();
     }
-    else if (type == typeof(UInt64))
+    else if (type == "float64-le")
     {
-      return typeof(UInt64Type);
+      return new Float64LEType();
     }
-    else if (type == typeof(Int32))
+    else if (type == "uint32")
     {
-      return typeof(Int32Type);
+      return new UInt32Type();
     }
-    else if (type == typeof(Int64))
+    else if (type == "uint64")
     {
-      return typeof(Int64Type);
+      return new UInt64Type();
     }
-    else if (type == typeof(byte[]))
+    else if (type == "int32")
     {
-      return typeof(BinaryType);
+      return new Int32Type();
+    }
+    else if (type == "int64")
+    {
+      return new Int64Type();
+    }
+    else if (type == "binary")
+    {
+      return new BinaryType();
     }
     else
     {
-      throw new Exception($"Invalid type: {type}");
+      throw new Exception($"Invalid type: {type.GetType()}");
     }
   }
 
-  public static string GetNameFromColumn(Type type)
+  public static ColumnType GetColumnFromType(Type type)
   {
-    if (type == typeof(StringType))
+    if (type == typeof(string))
+    {
+      return new StringType();
+    }
+    else if (type == typeof(bool))
+    {
+      return new BooleanType();
+    }
+    else if (type == typeof(float))
+    {
+      return new Float32Type();
+    }
+    else if (type == typeof(double))
+    {
+      return new Float64Type();
+    }
+    else if (type == typeof(UInt32))
+    {
+      return new UInt32Type();
+    }
+    else if (type == typeof(UInt64))
+    {
+      return new UInt64Type();
+    }
+    else if (type == typeof(Int32))
+    {
+      return new Int32Type();
+    }
+    else if (type == typeof(Int64))
+    {
+      return new Int64Type();
+    }
+    else if (type == typeof(byte[]))
+    {
+      return new BinaryType();
+    }
+    else
+    {
+      throw new Exception($"Invalid type: {type.GetType()}");
+    }
+  }
+
+  public static string GetNameFromColumn(ColumnType type)
+  {
+    if (type.GetType() == typeof(StringType))
     {
       return "string";
     }
-    else if (type == typeof(BooleanType))
+    else if (type.GetType() == typeof(BooleanType))
     {
       return "boolean";
     }
-    else if (type == typeof(Float32Type))
+    else if (type.GetType() == typeof(Float32Type))
     {
       return "float32";
     }
-    else if (type == typeof(Float32LEType))
+    else if (type.GetType() == typeof(Float32LEType))
     {
       return "float32-le";
     }
-    else if (type == typeof(Float64Type))
+    else if (type.GetType() == typeof(Float64Type))
     {
       return "float64";
     }
-    else if (type == typeof(Float64LEType))
+    else if (type.GetType() == typeof(Float64LEType))
     {
       return "float64-le";
     }
-    else if (type == typeof(UInt32Type))
+    else if (type.GetType() == typeof(UInt32Type))
     {
       return "uint32";
     }
-    else if (type == typeof(UInt64Type))
+    else if (type.GetType() == typeof(UInt64Type))
     {
       return "uint64";
     }
-    else if (type == typeof(Int32Type))
+    else if (type.GetType() == typeof(Int32Type))
     {
       return "int32";
     }
-    else if (type == typeof(Int64Type))
+    else if (type.GetType() == typeof(Int64Type))
     {
       return "int64";
     }
-    else if (type == typeof(BinaryType))
+    else if (type.GetType() == typeof(BinaryType))
     {
       return "binary";
     }
     else
     {
-      throw new Exception($"Invalid type: {type}");
+      throw new Exception($"Invalid type: {type.GetType()}");
     }
   }
 
@@ -1174,14 +1226,24 @@ public class SaneTsv
 
   public static byte[] SerializeCommentedTsv<T>(IList<T> data, string fileComment) where T : CommentedTsvRecord
   {
-    return SerializeTsv<T>(data, FormatType.COMMENTED_TSV);
+    return SerializeTsv<T>(data, FormatType.COMMENTED_TSV, fileComment);
   }
 
-  protected static byte[] SerializeTsv<T>(IList<T> data, FormatType tsvFormat)
+  protected static byte[] SerializeTsv<T>(IList<T> data, FormatType tsvFormat, string fileComment = null)
   {
     var bytes = new List<byte>();
 
-    var columnTypes = new List<Type>();
+    if (fileComment != null)
+    {
+      if (tsvFormat != FormatType.COMMENTED_TSV)
+      {
+        throw new Exception($"File comments are not valid for {tsvFormat}");
+      }
+
+      bytes.AddRange(Encoding.UTF8.GetBytes("#" + fileComment.Replace("\n", "\n#") + "\n"));
+    }
+
+    var columnTypes = new List<ColumnType>();
     var columnNames = new List<string>();
     var columnPropertyInfos = new List<PropertyInfo>();
     int columnCount = 0;
@@ -1197,8 +1259,8 @@ public class SaneTsv
 
       string headerName = attribute.ColumnName ?? property.Name;
       columnNames.Add(headerName);
-      Type headerType = attribute.ColumnType ?? GetColumnFromType(property.PropertyType);
-      if (tsvFormat == FormatType.SIMPLE_TSV && headerType != typeof(StringType))
+      ColumnType headerType = attribute.ColumnType ?? GetColumnFromType(property.PropertyType);
+      if (tsvFormat == FormatType.SIMPLE_TSV && headerType.GetType() != typeof(StringType))
       {
         throw new Exception($"Serializing Simple TSV requires all columns be of type string, but column '{headerName}' has type '{headerType}'");
       }
@@ -1278,7 +1340,7 @@ public class SaneTsv
     return bytes.ToArray();
   }
 
-  protected static void SerializeTsv<T>(IList<T> data, List<byte> bytes, PropertyInfo[] columnPropertyInfos, Type[] columnTypes, FormatType tsvFormat, int startIndex, int endIndex)
+  protected static void SerializeTsv<T>(IList<T> data, List<byte> bytes, PropertyInfo[] columnPropertyInfos, ColumnType[] columnTypes, FormatType tsvFormat, int startIndex, int endIndex)
   {
     // Serialize data
     for (int i = 0; i < data.Count; i++)
@@ -1293,16 +1355,16 @@ public class SaneTsv
           // Some fields definitely don't need escaping, so we add them directly to bytes
           bool skipEscaping = false;
 
-          if (columnTypes[j] == typeof(StringType))
+          if (columnTypes[j].GetType() == typeof(StringType))
           {
             fieldEncoded = Encoding.UTF8.GetBytes((string)datum);
           }
-          else if (columnTypes[j] == typeof(BooleanType))
+          else if (columnTypes[j].GetType() == typeof(BooleanType))
           {
             bytes.AddRange((bool)datum ? TrueEncoded : FalseEncoded);
             skipEscaping = true;
           }
-          else if (columnTypes[j] == typeof(Float32Type))
+          else if (columnTypes[j].GetType() == typeof(Float32Type))
           {
             if (datum is float f)
             {
@@ -1326,7 +1388,7 @@ public class SaneTsv
             }
             skipEscaping = true;
           }
-          else if (columnTypes[j] == typeof(Float32LEType))
+          else if (columnTypes[j].GetType() == typeof(Float32LEType))
           {
             if (LittleEndian)
             {
@@ -1342,7 +1404,7 @@ public class SaneTsv
               }
             }
           }
-          else if (columnTypes[j] == typeof(Float64Type))
+          else if (columnTypes[j].GetType() == typeof(Float64Type))
           {
             if (datum is double d)
             {
@@ -1366,7 +1428,7 @@ public class SaneTsv
             }
             skipEscaping = true;
           }
-          else if (columnTypes[j] == typeof(Float64LEType))
+          else if (columnTypes[j].GetType() == typeof(Float64LEType))
           {
             if (LittleEndian)
             {
@@ -1382,27 +1444,27 @@ public class SaneTsv
               }
             }
           }
-          else if (columnTypes[j] == typeof(UInt32Type))
+          else if (columnTypes[j].GetType() == typeof(UInt32Type))
           {
             bytes.AddRange(Encoding.UTF8.GetBytes(((UInt32)datum).ToString()));
             skipEscaping = true;
           }
-          else if (columnTypes[j] == typeof(UInt64Type))
+          else if (columnTypes[j].GetType() == typeof(UInt64Type))
           {
             bytes.AddRange(Encoding.UTF8.GetBytes(((UInt64)datum).ToString()));
             skipEscaping = true;
           }
-          else if (columnTypes[j] == typeof(Int32Type))
+          else if (columnTypes[j].GetType() == typeof(Int32Type))
           {
             bytes.AddRange(Encoding.UTF8.GetBytes(((Int32)datum).ToString()));
             skipEscaping = true;
           }
-          else if (columnTypes[j] == typeof(Int64Type))
+          else if (columnTypes[j].GetType() == typeof(Int64Type))
           {
             bytes.AddRange(Encoding.UTF8.GetBytes(((Int64)datum).ToString()));
             skipEscaping = true;
           }
-          else if (columnTypes[j] == typeof(BinaryType))
+          else if (columnTypes[j].GetType() == typeof(BinaryType))
           {
             fieldEncoded = (byte[])datum;
           }
@@ -1512,15 +1574,15 @@ public class SaneTsv
   public class TsvColumnAttribute : Attribute
   {
     public string ColumnName { get; }
-    public virtual Type ColumnType { get; }
+    public virtual ColumnType ColumnType { get; }
 
     public TsvColumnAttribute()
     {
-      ColumnType = typeof(StringType);
+      ColumnType = new StringType();
     }
     public TsvColumnAttribute(string columnName)
     {
-      ColumnType = typeof(StringType);
+      ColumnType = new StringType();
       ColumnName = columnName;
     }
   }
@@ -1528,27 +1590,19 @@ public class SaneTsv
   // TODO: Add column ordering
   public class TypedTsvColumnAttribute : TsvColumnAttribute
   {
-    public override Type ColumnType { get; }
+    public override ColumnType ColumnType { get; }
 
     public TypedTsvColumnAttribute() { }
 
     public TypedTsvColumnAttribute(string columnName) : base(columnName) { }
 
-    public TypedTsvColumnAttribute(string columnName, Type columnType) : base(columnName)
+    public TypedTsvColumnAttribute(string columnName, string columnType) : base(columnName)
     {
-      if (columnType.BaseType != typeof(ColumnType))
-      {
-        throw new Exception("Column type must inherit from SaneTsv.ColumnType");
-      }
-      ColumnType = columnType;
+      ColumnType = GetColumnFromString(columnType);
     }
 
-    public TypedTsvColumnAttribute(Type columnType)
+    public TypedTsvColumnAttribute(ColumnType columnType)
     {
-      if (columnType.BaseType != typeof(ColumnType))
-      {
-        throw new Exception("Column type must inherit from SaneTsv.ColumnType");
-      }
       ColumnType = columnType;
     }
   }