FirstOrDefault: Default value other than null

.net linq
Sachin Kainth picture Sachin Kainth · Oct 19, 2012 · Viewed 135.9k times · Source

As I understand it, in Linq the method FirstOrDefault() can return a Default value of something other than null. What I haven't worked out is what kind of things other than null can be returned by this (and similar) method when there are no items in the query result. Is there any particular way that this can be set up so that if there is no value for a particular query some predefined value is returned as the default value?

Answer

Jon Skeet picture Jon Skeet · Oct 19, 2012

As I understand it, in Linq the method FirstOrDefault() can return a Default value of something other than null.

No. Or rather, it always returns the default value for the element type... which is either a null reference, the null value of a nullable value type, or the natural "all zeroes" value for a non-nullable value type.

Is there any particular way that this can be set up so that if there is no value for a particular query some predefined value is returned as the default value?

For reference types, you can just use:

var result = query.FirstOrDefault() ?? otherDefaultValue;

Of course this will also give you the "other default value" if the first value is present, but is a null reference...

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