How to ignore 'where' and 'order by' condition if the column is null in LINQ

Question

I have list of transaction objects and want to order them by certain condition depending on view user is currently on. The problem I have is that in order to add a condition in a where clause, first I need to check if it is null or not to prevent null pointer exception. This causes records with the column null being filtered out(and I want to include them at bottom of the list). How can I modify the query so that it ignores the conditions(where and order by) if that column is null and still append them to the result set? This is one example query: ``` transactions = transactions .Where(t => t.PurchaseRequisition != null && t.Award != null && t.PurchaseRequisition.RequisitionedBy != null) .OrderBy(t => t.Award.ContractNumber). ThenBy(t => ToSafeString(t.Award.ContractNumber)). ThenBy(t => ToSafeString(t.PurchaseRequisition.RequisitionedBy.FullName)); public string ToSafeString(string s) { return s ?? String.Empty; } ``` // I want records where PurchaseRequisition or Award is null to be…

Accepted Answer

You simply need to modify your `OrderBy` and `ThenBy` clauses:

```
.OrderBy(t => t.Award == null || t.Award.ContractNumber == null)
.ThenBy(t => t.Award == null ? "" : ToSafeString(t.Award.ContractNumber))
.ThenBy(t => t.PurchaseRequisition == null ? "" 
             : ToSafeString(t.PurchaseRequisition.RequisitionedBy.FullName));
```

Now you can completely remove the `Where` clause.

How to ignore 'where' and 'order by' condition if the column is null in LINQ

Solution

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