CODEWITHSUNDEEP
c#linq
stzvggmd
stzvggmd

Reputation: 134

Faster way to create objects from array using LINQ?

I have a CSV list of values which I am converting into a User object. I have done this via a foreach loop but wonder if there's a way of doing this via LINQ in a more efficient manner? I've tried a combination of using Select and Where but cannot seem to find a method specific to my case.

User.cs:

public class User
{
    public string FirstName {get; set;}
    public string LastName { get; set; }
    public string Password { get; set; }
}

Current way of doing it:

var lines = File.ReadAllLines(filepath).Select(x => x.Split(';'));

var users = new List<User>();

foreach (var line in lines)
{
    var user = new User
    {
        FirstName = line[0],
        LastName = line[1],
        Password = line[2]
    };

    users.Append(user);
}

Upvotes: 0

Views: 704

Answers (2)

Bruno Belmondo
Bruno Belmondo

Reputation: 2367

What about :

var users = lines.Select(line=>new User
        {
            FirstName = line[0],
            LastName = line[1],
            Password = line[2]
        }).ToList();

The last ToList is optional whether you want to collect immediatly or not.

You can even in one step like:

var users = File.ReadAllLines(filepath).Select(x=>
{ 
    var line = x.Split(';');
    return new User
        {
            FirstName = line[0],
            LastName = line[1],
            Password = line[2]
        };
}).ToList();

Edit: To clarify I decompose :

var users = File.ReadAllLines("filepath").Select(BuildFromLine).ToList();

The select takes as a parameter a Function with a string as input and whatever as output (here a user). Then I have a function to build my users. In the above notation I transformed the function in an anonymous lambda. Note that for clarity I kept the name x for the parameter of the function but in the real world I would have renamed it to reflect what it really is (x becomes line and line becomes tokens).

public static User BuildFromLine(string x)
{
    var line = x.Split(';');
    return new User
    {
        FirstName = line[0],
        LastName = line[1],
        Password = line[2]
    };
}

Upvotes: 7

Michał Turczyn
Michał Turczyn

Reputation: 37460

You could to it entirely with LINQ:

var users = File.ReadAllLines(path)
  .Select(line => line.Split(';'))
  .Select(splitLine => new User { FirstName = splitLine[0], LastName = splitLine[1], Password = splitLine[2] })
  .ToArray();

Upvotes: 0

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