Lazily reading a file line-by-line via an C# with Example

IEnumerable 
When working with large files, you can use the System.IO.File.ReadLines method to read all lines from a file into 
an IEnumerable. This is similar to System.IO.File.ReadAllLines, except that it doesn't load the whole file 
into memory at once, making it more efficient when working with large files. 
IEnumerable AllLines = File.ReadLines("file_name.txt", Encoding.Default); 
The second parameter of File.ReadLines is optional. You may use it when it is required to specify encoding. 
It is important to note that calling ToArray, ToList or another similar function will force all of the lines to be loaded 
at once, meaning that the benefit of using ReadLines is nullified. It is best to enumerate over the IEnumerable using 
a foreach loop or LINQ if using this method.