Stop LINQ Query if Default Value is Returned at Any Point

c#, default-value, linq, short-circuiting, syntactic-sugar

Solution

In cases where you want to resolve the set to a single item and manipulate that item, but still gracefully handle situations where that item may not be found in the set, you can can delay the `FirstOrDefault` until the very end, like this:

var reversed = testList
    .Where(x => x == "hello")
    .Select(x => x.Reverse())
    .FirstOrDefault();

Or equivalently

var reversed = testList
    .Where(x => x == "hello")
    .Select(Enumerable.Reverse)
    .FirstOrDefault();

This will return `null` if no items are in the list that satisfy the condition specified in the `Where` method. The performance difference here will be at most negligible. It won't require looping through the `testList` any more than the original code, since once the first element is found, the result is immediately returned.

Problem

Is there syntactic sugar or a method to "short-circuit" a LINQ statement within the same line when written in fluent syntax? For example if `null` is returned by a `FirstOrDefault` call, is it possible to return null otherwise continue with the rest of the method chain? ``` List<string> testList = new List<string>() { "some", "strings" }; var reversed = testList.FirstOrDefault(x => x == "hello").Reverse(); ``` The `FirstOrDefault` call will return null so the statement will throw an `ArgumentNullException` on the `Reverse` call. Is there a way of stopping before the `Reverse` call since the default value was returned at that point? (I know that the query can be broken into another line and `default(T)` can be checked before `Reverse` or, for simple cases, the conditional operator (`?:`) can be used but I'm curious if I'm missing a particular feature for longer/more complex chains) Edit - To clarify this is just an example to show the idea, it's not part of any actual code. I'd like to avoid exceptions being thrown as it would be more performant to just split the line and do a check.

Original source