How to use a conditional or in linq and C#-CodePudding

In the following GetByExpression, sometimes the r.branchid is null. How do I add a conditional in there so it utilises a different field (r.Invoice.Branch.Id) to check against when r.branchid is null?

var t = receiptRepo
 .GetByExpression(r => r.BranchId == branchId)
 .Where(r => r.Date == selectedDate && r.BatchId == null)
 .ToList();

CodePudding user response：

Use a ternary operation

(r.BranchId != null? r.BranchId:r.Invoice.Branch.Id ) == branchId //or whatever you want to compare

CodePudding user response：

You can try using null-coalescing operator ??:

r => (r.BranchId ?? r.Invoice.BranchId) == branchId

Here if r.BranchId is null we use r.Invoice.BranchId to compare with branchId. Note, that we can chain ?? operators, e.g.

r => (r.BranchId ?? r.Invoice.BranchId ?? r.Bill.BranchId) == branchId

we try BranchId if it's null, we have a look at r.Invoice.BranchId and if it's null we get r.Bill.BranchId etc.

Your Linq query can be

var t = receiptRepo
  .GetByExpression(r => (r.BranchId ?? r.Invoice.BranchId) == branchId)
  .Where(r => r.Date == selectedDate && r.BatchId == null)
  .ToList();

CodePudding user response：

You can do this:

var t = receiptRepo
        .GetByExpression(r => (r?.BranchId ?? r.Invoice.BranchId) == branchId)
        .Where(r => r.Date == selectedDate && r.BatchId == null)
        .ToList();