The ?? null coalescing operator using with LINQ
Filed under: T-Sql to Linq Upgrade — admin @ 5:02 pm
T-Sql coalesce usage:
select c.ContactName, EmpID= coalesce(o.EmployeeID,-1)
from Customers c
left outer join Orders o on o.CustomerID = c.CustomerID
Same Query with Linq ?? operator:
DataClassesDataContext db = new DataClassesDataContext();
var Cust = from c in db.Customers
join o in db.Orders on c.CustomerID equals o.CustomerID into g
from o in g.DefaultIfEmpty()
select new {c.ContactName, EmpID = o.EmployeeID ?? -1 };
how should i use ?? operator in the following coding.
int iNewOitem = dc.tOrderDetails.Max(u => u.OrderItemId)+ 1;
Objective : if the database value is null ” dc.tOrderDetails.Max(u => u.OrderItemId) ” should return the value “0″ else it may return the exact maximum value .
how is it possible ? hope u can understand ?
regards,
Durai karthik
Comment by Duraikarthik — April 16, 2008@ 4:35 pm
If you only want to check value of u.OrderItemId, you should use like;
int iNewOitem = dc.tOrderDetails.Max(u => u.OrderItemId ?? 0)+ 1;
Comment by admin — April 16, 2008@ 5:47 pm
It gives the following error after i used this coding
int iNewOitem = dc.tOrderDetails.Max(u => u.OrderItemId ?? 0) + 1;
Operator ‘??’ cannot be applied to operands of type ‘int’ and ‘int’
Kindly give me a solution.
Comment by Durai karthik — April 16, 2008@ 6:41 pm
try this one,
int iNewOitem = dc.tOrderDetails.Max(u => (int?)u.OrderItemId ?? 0) + 1;
Comment by admin — April 17, 2008@ 12:40 pm