How Best to Read a File into List<String>

How best to read a File into Liststring

var logFile = File.ReadAllLines(LOG_PATH);
var logList = new List<string>(logFile);

Since logFile is an array, you can pass it to the List<T> constructor. This eliminates unnecessary overhead when iterating over the array, or using other IO classes.

Actual constructor implementation:

public List(IEnumerable<T> collection)
{
        ...
        ICollection<T> c = collection as ICollection<T>;
        if( c != null) {
            int count = c.Count;
            if (count == 0)
            {
                _items = _emptyArray;
            }
            else {
                _items = new T[count];
                c.CopyTo(_items, 0);
                _size = count;
            }
        }   
        ...
} 

Reading in .txt and using header string as list name

Since lists don't exactly have "names" (what you might confuse with reference), maybe you could use dictionaries:

my_list = [line.split() for line in open("file.txt", "r") ]

lists = {name: [] for name in my_List[0]}  # my_List[0] = ['Name1','Name2']

for i in range(1,len(my_list)):
    lists['Name1'].append(my_list[i][0])
    lists['Name2'].append(my_list[i][1])

But in general try to avoid reading a whole file to a list (or a string). It is much more efficient to use iterators, where possible. Your case most definetly allows it:

with open("file.txt") as in_f:
    first_line = in_f.readline().strip().split()

    lists = {name: [] for name in first_line}

    for line in in_f:
        line_as_list = line.split()
        lists['Name1'].append(line_as_list[0])
        lists['Name2'].append(line_as_list[1])

If by name you mean reference to a list, as in create a variable with that name that points to a list you might use exec:

with open("file.txt") as in_f:
    first_line = in_f.readline().strip().split()  # first_line = ['Name1','Name2']

    for name in first_line:
        exec(f"{name} = []")

    for line in in_f:
        line_as_list = line.split()
        Name1.append(line_as_list[0])
        Name2.append(line_as_list[1])

Read the docs about exec

How to write and read list to text file that contains user input using c#

You can use the static methods of the System.IO.File class. Their advantage is that they open and close files automatically, thus reducing the task of writing and reading files to a single statement

File.WriteAllLines(yourFilePath, category);

You can read the lines back into a list with

 category = new List(ReadLines(yourFilePath));

ReadLines returns an IEnumerable<string> that is accepted as data source in the constructor of the list.

or into an array with

string[] array = ReadAllLines(yourFilePath);

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Your solution does not write anything to the output stream. You are initializing a TextWriter but not using it. You would use it like

tw.WriteLine(someString);

Your code has some problems: You are declaring a category variable k, but you never assign it a category. Your list is not of type category.

A better solution would work like this

var categories = new List<Category>(); // Create a categories list.
while (true) { // Loop as long as the user enters some category name.
    Console.WriteLine("Enter name of category: ");
    string s = Console.ReadLine(); // Read user entry.
    if (String.IsNullOrWhiteSpace(s)) {
        // No more entries - exit loop
        break;
    }

    // Create a new category and assign it the entered name.
    var category = new Category { name = s };

    //TODO: Prompt the user for more properties of the category and assign them to the
    // category.

    // Add the category to the list.
    categories.Add(category);
}
File.WriteAllLines(yourFilePath, categories.Select(c => c.name));

The Category type should be class. See: When should I use a struct instead of a class?

Read and convert row in text file into list of string

The reason your code doesn't work is you are trying to use split on a list, but it is meant to be used on a string. Therefore in your example you would use row2[0] to access the first element of the list.

my_list = row2[0].split("    ")

Alternatively, if you have access to the numpy library you can use loadtxt.

import numpy as np

f = np.loadtxt("data.txt", dtype=str, skiprows=1)

print (f)
# ['second_row_1' 'second_row_2' 'second_row_3']

The result of this is an array as opposed to a list. You could simply cast the array to a list if you require a list

print (list(f))
#['second_row_1', 'second_row_2', 'second_row_3']

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