Embracing the Elegance of One-Liners: Converting a C# LINQ List Query to String Delimiter

In the world of programming, there is an undeniable beauty in concise and elegant code. One-liners, in particular, have a charm of their own, offering simplicity and efficiency. Today, I would like to share my love for one-liner codes and showcase a fascinating piece of LINQ algorithm I recently discovered, known as “Aggregate.” In this blog post, we will explore how this algorithm can be used to convert a C# LINQ list query to a string delimiter.

What was my solution for the one-liner?

In my recent project, I encountered a scenario where I needed to extract a list of user emails from a User table in a database and convert them into a single string, with each email separated by a comma. This would then be used for the email CC’d list of contacts. Traditionally, this task might involve writing multiple lines of code, iterating through the list, and manually appending the delimiter. However, with my newfound knowledge of the “Aggregate” method in LINQ, I discovered an elegant solution that allowed me to achieve this transformation in a single line of code. By using the “Aggregate” method, I was able to concatenate the emails while automatically adding the comma delimiter between each email, resulting in a concise and efficient one-liner solution.

The C# Linq One-Liner

string emailCC = db.{USERS}.Where(x => x.{db2} == {condition}).Select(x =>x.email).ToList().Aggregate((a, b) => a + ',' + b);
  1. db.{USERS}: This line refers to the User table in the database
  2. .Where(x => x.{db2} == {condition}): This is a filtering condition applied to the “db.{USERS}” table.
  3. .Select(x => x.email): This line selects the “email” property from each of the filtered users, resulting in a list of email strings.
  4. .ToList(): The “ToList()” method converts the IEnumerable collection of email strings into a List<string> object. This step is necessary to use the “Aggregate” method.
  5. .Aggregate((a, b) => a + ',' + b): Here comes the core part of the code. The “Aggregate” method is used to iteratively concatenate the email strings from the list into a single string. The lambda expression (a, b) => a + ',' + b defines how the aggregation should be performed. It takes two input strings, a and b, and concatenates them with a comma delimiter in between. The method applies this operation successively, accumulating the result until all the email strings are concatenated.
  6. string email2 = ...: Finally, the result of the aggregation is assigned to the variable email2, which holds the final string with the emails delimited by commas.

In summary, this one-liner code retrieves a list of user emails from the “db.{USERS}” table in the database, filters them based on a specific condition, and converts them into a single string with commas as delimiters using the powerful “Aggregate” method.


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