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

Question

I am working on Console Application and I am trying to save list to txt file and read that data later.

In program user inputs name of category and I am not sure how to save that with list in txt file.

Struct Category that holds name.

struct Category
{
    public string name;
}

This is my code so far.

Category k;

Console.WriteLine("Enter name of category: ");
k.name = Console.ReadLine();

List<String> category = new List<string>();


TextWriter tw = new StreamWriter("../../dat.txt");

foreach (string k in category)
{

    string[] en = s.Split(','); 
    category.Add(k.name); // Here I am not sure how to save name
}
tw.Close();

StreamReader sr = new StreamReader("../../dat.txt");

string data = sr.ReadLine();

while (data != null)
{

    Console.WriteLine(data);
    data = sr.ReadLine();
}
sr.Close();

It doesn't give me any error but it's not writing name to txt file.

SOLUTIN

string filePath = @"../../datoteka.txt";
List<String> kategorije = File.ReadAllLines(filePath).ToList();

foreach (string s in kategorije)
{

Console.WriteLine(s);

}
kategorije.Add(k.naziv);
File.WriteAllLines(filePath,kategorije);

You don't actually write anything using the TextWriter i.e. I would expect to see tw.WriteLine(k.Name) or similar. — SpruceMoose
– SpruceMoose, Commented Jan 28, 2018 at 18:24
After category.Add(k.name) add a line tw.WriteLine(k.name) ... — McGuireV10
– McGuireV10, Commented Jan 28, 2018 at 18:27
Quite a few problems: you never use tw to actually write anything; you try to foreach through a new, empty list; you define k as a Category struct, then again as the foreach variable; whatever s is in s.Split isn't defined in the code you've shown; the List contains string values, not your Category struct... — McGuireV10
– McGuireV10, Commented Jan 28, 2018 at 18:35

Olivier Jacot-Descombes · Accepted Answer · 2018-01-28 19:32:54Z

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);

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?

Thank you for your answer. I managed to fix my code based on it. If you check my question I have put it as solution. :) @Olivier Jacot-Descombes

lazydeveloper · Accepted Answer · 2018-01-28 18:58:33Z

You are not using WtiteLine to write content. Add below code in your solution after

category.Add(k.name);
tw.WriteLine(someString);

https://learn.microsoft.com/en-us/dotnet/csharp/programming-guide/file-system/how-to-write-to-a-text-file

Find below sample code for read and write.

class WriteTextFile
{
    static void Main()
    {
        System.IO.File.WriteAllLines(@"C:\Users\Public\TestFolder\WriteLines.txt", lines);

        string text = "A class is the most powerful data type in C#. Like a structure, " +
                       "a class defines the data and behavior of the data type. ";

        System.IO.File.WriteAllText(@"C:\Users\Public\TestFolder\WriteText.txt", text);

        using (System.IO.StreamWriter file = 
            new System.IO.StreamWriter(@"C:\Users\Public\TestFolder\WriteLines2.txt"))
        {
            foreach (string line in lines)
            {                   
                if (!line.Contains("Second"))
                {
                    file.WriteLine(line);
                }
            }
        }    
        using (System.IO.StreamWriter file = 
            new System.IO.StreamWriter(@"C:\Users\Public\TestFolder\WriteLines2.txt", true))
        {
            file.WriteLine("Fourth line");
        }
    }
}

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