Make EditableText.Lines return a read-only list

Author: Kapil Borle

Engine/EditableText.cs

@@ -24,7 +24,7 @@ public class EditableText
         /// <summary>
         /// The lines in the Text.
         /// </summary>
-        public string[] Lines { get { return lines.ToArray(); } }
+        public IList<string> Lines => lines.ReadOnly();
 
         /// <summary>
         /// The new line character in the Text.
@@ -118,8 +118,8 @@ public bool IsValidRange(Range range)
                 throw new ArgumentNullException(nameof(range));
             }
 
-            return range.Start.Line <= Lines.Length
-                && range.End.Line <= Lines.Length
+            return range.Start.Line <= Lines.Count
+                && range.End.Line <= Lines.Count
                 && range.Start.Column <= Lines[range.Start.Line - 1].Length
                 && range.End.Column <= Lines[range.End.Line - 1].Length + 1;
         }