Query: invalid SQL generated for groupby aggregate query projecting key sum of group key with itself

[maumar]

query:

var query = (from o in ctx.Orders
                             join c in ctx.Customers
                                 on o.CustomerID equals c.CustomerID into grouping
                             from c in grouping.DefaultIfEmpty()
                             select o)
                        .GroupBy(o => o.OrderID)
                        .Select(
                            g => new
                            {
                                Value = g.Key + g.Key,
                                Average = g.Average(o => o.OrderID)
                            });

                var result = query.ToList();

sql:

SELECT [o].[OrderID] AS [Key] + [o].[OrderID] AS [Key] AS [Value], AVG(CAST([o].[OrderID] AS float)) AS [Average]
FROM [Orders] AS [o]
LEFT JOIN [Customers] AS [c] ON [o].[CustomerID] = [c].[CustomerID]
GROUP BY [o].[OrderID]

Exception:

Incorrect syntax near '+'.

[smitpatel]

Duplicate of #12826