What is LINQ SelectMany?

LINQ SelectMany is a LINQ Query Operator and comes under the Projection Operators category. It’s a nifty little gizmo that projects the results of a nifty little function into an IEnumerable. The main reason it’s a nifty little tidbit is because it allows you to pick from any nested collection of arrays. In essence, it is a new form of SQL.

The LINQ SelectMany operator is one of the more complicated operators in the language and it’s only really good at the more advanced tasks. In order to do it right you need to have access to an object that was attached to the original table. As a result you will need to use a selector, a collection of arrays and a set of data types. As you can imagine, this will prove to be a bit of a pain, especially if you’re working with a large database. However, it does come in handy from time to time and there are many reasons for doing so.

LINQ SelectMany is not the first Projection Operator in the language and you won’t be the first to use it. In fact, there are many, many versions of the select and selectmany operators, each with its own advantages and disadvantages. One of the more common pitfalls is that you don’t really know what to expect. For example, you may be surprised to find that the selectmany operator actually projects each element of a sequence into an IEnumerable. This may be a good idea in some cases, for example if you have a lot of columns that need to be checked for unique values. In other cases, you might find that you’ve just added a large number of rows that you can no longer re-arrange to your liking. In such cases, it’s probably a good idea to just use a re-queryable selector to avoid a major headache. For the most part, this is the best way to go. Despite its limitations, it’s a nifty little function that you’ll definitely want to take a look at if you’re working with large tables. For example, if you’re looking to update a table of numbers, then the select operator is a good bet, and you can be sure you’ll have the most up-to-date results when you’re done. In fact, you may want to keep a copy of your original table on hand just in case. For example, if you’re working with a data set containing phone numbers, you may find that it’s a good idea to query your phone numbers for unique numbers, which you can then re-query to find the number you’re looking for.

The LINQ SelectMany is a worthy contender in the Projection Operators category. As such, it may be difficult to pick a winner. However, if you do, the first thing you should do is to look at the pros and cons of each.

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