How Can I Add Items to an IEnumerable Collection?

Adding Items to IEnumerable Collections

Enumerable collections, represented by the IEnumerable interface, provide a way to iterate over a sequence of values without having direct access to the collection itself. Unlike List, which allows for item modification and addition, IEnumerable collections do not inherently possess such functionality.

Consider the following example:

IEnumerable<string> items = new string[] { "msg" };
items.ToList().Add("msg2");

After executing this code, the number of items in the collection remains at one. This is because IEnumerable does not represent a mutable collection. It simply provides a way to access elements sequentially.

To achieve the desired behavior of adding items to an IEnumerable collection, you must use an approach that creates a new IEnumerable object with the appended item included. One way to accomplish this is through the Enumerable.Concat method:

items = items.Concat(new[] { "foo" });

This line of code creates a new IEnumerable object that contains all elements of the original items collection, followed by the additional item "foo." The new object will reflect any changes made to the original collection, ensuring that you always have an up-to-date representation of the data.

It's important to note that this approach does not modify the original items array. Instead, it creates a new collection object that provides an updated view of the data.

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