By assigning a default value to the collection, the DefaultIfEmpty method of LINQ may handle empty or null collections. If the input sequence is empty or null, the DefaultIfEmpty method delivers a single default value instead of a new sequence containing the items of the input sequence.   When a collection is empty, you may use the DefaultIfEmpty method to return a default value, as seen in the following example:  List numbers = new List();
var defaultedNumbers = numbers.DefaultIfEmpty(-1);  In this example, the empty numbers list is passed to the DefaultIfEmpty method, which returns a new sequence with a single element that has the default value of -1.   Additionally, you can use this method to give null collections a default value, like in the example below:  List numbers = null;
var defaultedNumbers = numbers.DefaultIfEmpty(-1);  In this example, the null numbers list is passed to the DefaultIfEmpty method, which returns a new sequence with a single element that has the default value of -1.   It can be used in a variety of situations, such as handling empty or null lists, arrays, etc. It is handy when you wish to manage cases when the input collection is empty or null and return a default value in those cases.   In conclusion, empty or null collections can be handled by using LINQ's DefaultIfEmpty method, which assigns a default value to the collection. If the input sequence is empty or null, the DefaultIfEmpty method delivers a single default value instead of a new sequence containing the items of the input sequence. It can be used in a variety of situations, such as handling empty or null lists, arrays, etc. It is handy when you wish to manage cases when the input collection is empty or null and return a default value in those cases.