Question

Novice question. What collection type should I use to store such structure?

Files collection
---------------
FileId: Int
FileName : String
Path: String

I will need to store several files data into that collection, find Path by FileId field, delete item by FileId field.

Answer 1

Since you have several pre-defined pieces of information that you want associated with each value instance, I would start by defining a structure to hold the information required for each file:

public struct CustomFileInfo  //pick a name that avoids conflicts with System.IO
{
    public readonly int FileId;
    public readonly string FileName;
    public readonly string Path;

    // constructor
    public CustomFileInfo(int fileId, string fileName, string path)
    {
        this.FileId = fileId;
        this.FileName = fileName;
        this.Path = path;
    }
}

And then I would use a generic collection (such as a List<T>) to hold instances of that structure:

List<FileInfo> myFiles = new List<FileInfo>();

Alternatively, you could use a Dictionary<TKey, TValue>, with the FileId as the key and the FileInfo structure as the value. For example:

Dictionary<int, FileInfo> myFiles = new Dictionary<int, FileInfo>();

The advantage of a dictionary is that it provides faster lookup time when searching for a file by its ID. This is because a dictionary is implemented internally using a hash table.

EDIT: Note that mutable structs are evil. If you need to be able to change the individual pieces of information that describe a file (and I can’t imagine why you would), you should declare CustomFileInfo as a class instead of a struct.