Linq questions: First vs Firstordefault, single vs singleordefault, convert generic list to non generic type.

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Explanation of Linq methods First, FirstOrDefault, Single, SingleOrDefault and converting generic list to non generic type.

First returns the first element of a sequence, throws an exception if sequence is empty.
FirstOrDefault returns the first element of a sequence or default value if sequence is empty.
Single returns the only element of a sequence, throws an exception if sequence has more than one element or is empty.
SingleOrDefault returns the only element of a sequence or default value if sequence is empty or has more than one element.
To convert a generic list to non generic type, use the Cast method followed by ToArray or ToList.

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