LINQ Left Join with use of Where Or syntax - linq

Question

How can I migrate this stored procedure into LINQ
DECLARE #customerIDs TABLE (customerID INT)
DECLARE #c INT
if (#customerName != '')
BEGIN
INSERT INTO #customerIDs
select id from customer
where name like '%' + #customerName + '%'
SELECT #c = COUNT(*) FROM #customerIDs
END
else
SET #c = 0
-- Insert statements for procedure here
SELECT DISTINCT l.*, dbo.GetListOfBranches(l.id) as 'list_of_branches', dbo.GetTopLevelCustomer(cid.customerID) FROM [login] l
LEFT JOIN login_to_customer ltc ON ltc.login_id = l.id
LEFT JOIN #customerIDs cid ON cid.customerID = ltc.customer_id
WHERE
(#c = 0 OR ltc.customer_id = cid.customerID) AND
(l.surname LIKE '%' + ISNULL(#surname, l.surname) + '%') AND
(l.forename LIKE '%' + ISNULL(#forename, l.forename) + '%') AND
(user_type = ISNULL(#userType, user_type)) AND
(l.active = ISNULL(#active, l.active))
ORDER BY surname ASC
I have got this so far:
List<Int32> customerIds = new List<int>();
if (!String.IsNullOrEmpty(customerName))
{
CustomerDataContext custDataContext = new CustomerDataContext();
customerIds = (from a in custDataContext.Customers
where a.name.Contains(customerName)
select a.id).ToList<Int32>();
}
LoginDataContext dataContext = new LoginDataContext();
var query = (from t in dataContext.logins
join t2 in dataContext.login_to_customers on t.id equals t2.login_id into a
from subquery in a.DefaultIfEmpty()
select new { t, listOfBranches = dataContext.GetListOfBranches(t.id), topLevelCustomer = dataContext.GetTopLevelCustomer(t.id) });
I need would then do a
if (customerIds.Count() > 0)
{
query = query.Where(a => customerIds.Contains(a.t.customer_id))
}
but as I need to perform the distinct I cant have the customer_id column in the query. Is there a way to include the
LEFT JOIN #customerIDs cid ON cid.customerID = ltc.customer_id
WHERE
(#c = 0 OR ltc.customer_id = cid.customerID)
Within the LINQ?
Thanks,
Richard