How Can LINQ Simplify Data Pivoting and Restructuring?

Pivoting Data with LINQ

In certain scenarios, restructuring data into a different format becomes necessary. One common task is pivoting data, transforming it from a tabular structure into a more condensed layout. While traditional iterative approaches like foreach loops can accomplish this, they introduce challenges with collection modifications during iteration. Enter LINQ, a powerful querying language that simplifies data manipulation, offering a cleaner and more efficient solution for pivoting data.

Consider a collection of objects containing an enumeration (TypeCode) and a User instance. The goal is to flatten this collection into a grid-like structure, where each TypeCode corresponds to a column and the User names are arranged in rows.

LINQ provides a straightforward way to achieve this pivot operation. By grouping the collection by TypeCode and then selecting the User names as an array for each group, we can effectively create columns. The following code snippet demonstrates this approach:

// Sample data
var data = new[] {
    new { TypeCode = 1, User = "Don Smith" },
    new { TypeCode = 1, User = "Mike Jones" },
    new { TypeCode = 1, User = "James Ray" },
    new { TypeCode = 2, User = "Tom Rizzo" },
    new { TypeCode = 2, User = "Alex Homes" },
    new { TypeCode = 3, User = "Andy Bates" }
};

// Group by TypeCode and select User name arrays
var groups = from d in data
              group d by d.TypeCode
              into grp
              select new {
                  TypeCode = grp.Key,
                  Users = grp.Select(d2 => d2.User).ToArray()
              };

After creating the columns, we need to determine the total number of rows, which is the maximum length of any user array in the groups. With this information, we can iterate through each group and display the corresponding user names, padding with null values where necessary.

// Find total number of rows
int rows = groups.Max(grp => grp.Users.Length);

// Output columns
foreach (var grp in groups) {
    Console.Write(grp.TypeCode + "\t");
}
Console.WriteLine();

// Output rows
for (int i = 0; i < rows; i++) {
    foreach (var grp in groups) {
        Console.Write((i < grp.Users.Length ? grp.Users[i] : null) + "\t");
    }
    Console.WriteLine();
}

By leveraging LINQ's group-by and selection capabilities, this code enables us to pivot the data and generate the desired output in a concise and efficient manner.

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