the transaction is not really needed there ... it helps with nothing.

Dapper.Contrib/SqlMapperExtensions.cs

@@ -146,8 +146,7 @@ private static string GetTableName(Type type)
         /// <returns>Identity of inserted entity</returns>
         public static long Insert<T>(this IDbConnection connection, T entityToInsert, IDbTransaction transaction = null, int? commandTimeout = null) where T : class
         {
-            using (var tx = connection.BeginTransaction())
-            {
+            
             var type = typeof(T);
 
             var name = GetTableName(type);
@@ -180,10 +179,9 @@ private static string GetTableName(Type type)
             sb.Append(") ");
             connection.Execute(sb.ToString(), entityToInsert, transaction: transaction, commandTimeout: commandTimeout);
             //NOTE: would prefer to use IDENT_CURRENT('tablename') or IDENT_SCOPE but these are not available on SQLCE
-                var r = connection.Query("select @@IDENTITY id");
-                tx.Commit();
+            var r = connection.Query("select @@IDENTITY id", transaction: transaction, commandTimeout: commandTimeout);
             return (int)r.First().id;
-            }
+            
         }
 
         /// <summary>