Add .NET Core 2.1 versions

worker/dotnet/Worker/Entities/Vote.cs

@@ -0,0 +1,16 @@
+using System.ComponentModel.DataAnnotations;
+using System.ComponentModel.DataAnnotations.Schema;
+
+namespace Worker.Entities
+{
+    [Table("votes")]
+    public class Vote
+    {
+        [Column("id")]
+        [Key]
+        public string VoterId { get; set; }
+
+        [Column("vote")]
+        public string VoteOption { get; set; }
+    }
+}

worker/dotnet/Worker/Entities/VoteContext.cs

@@ -0,0 +1,19 @@
+using Microsoft.EntityFrameworkCore;
+
+namespace Worker.Entities
+{
+    public class VoteContext : DbContext
+    {
+        private static bool _EnsureCreated;
+        public VoteContext(DbContextOptions options) : base(options)
+        {
+            if (!_EnsureCreated)
+            {
+                Database.EnsureCreated();
+                _EnsureCreated = true;
+            }
+        }
+
+        public DbSet<Vote> Votes { get; set; }
+    }
+}