Read a txt file, insert into an array and display in a textbox in C#

Question

I need to open the txt file with the data already inserted with three columns and separated by ';' and after opening the file I insert it into an Array with List, save the data and need the values inserted inside the file to appear in a textbox. However I need to take an exact and/or close value of the value typed in a previous textbox and these value is in column 1 of the file and when the value is selected I need it to show me the value of column 3 of the same row of the selected value.

I already managed to open the file, throw the data of the file in the Array, but it does not return me the values of column 3 that I need. I finished this code, but it shows me the last line of the file with the three columns. I believe the error is from the foreach, because it reads only the last line. And I don’t know how to do an If (if it’s the If I need to do) so that it reads the value of the previous textbox and read the next value in the file and select column 3. I have tried to make if or insert the iterations inside the code in the foreach, but no success.

Note: I have read several websites/forums about this, but none was according to what I need.

In the txt file is thus the data:

For example: the value typed in the previous textbox gave 173.10 so the next value in the txt file is 172.0585213 so I want it to select this value and show the value of the third column (16) in the following textbox.

I’ll enter my code below:

    List<string> lista = new List<string>(); 

        string dados = (@"C: .... .txt"); // // caminho do documento em C: com a extensão em .txt
        string linha; // //declara uma variável para receber linha por linha do doc.

        using (StreamReader Str = new StreamReader(dados)) // a leitura do arquivo.
        {
            while ((linha = Str.ReadLine()) != null) //cria um loop para adicionar linha por linha do doc até sua ultima linha.
            {
                lista.Add(linha);
            }

           for (int i = 0; i < dados.Length; i++) // Percorro o array e para cada linha.
            {
                foreach (var item in lista)
                {

                    var coluna1 = Convert.ToInt32(item[0]);
                    var coluna3 = Convert.ToInt32(item[2]);

                    var valores = File.ReadAllLines(dados).Select(linha => linha.Split(new[] { ';' }, StringSplitOptions.RemoveEmptyEntries))
                        .Where(Split => Split.Length >= 3).Select(Split => Split[2]).ToList();
                    Txtbox2.Text = (item).ToString();

                }

            }

Answer 1

I tested via console application, but it is fully possible to use this class in winforms.

class Arquivo_Dados
{
    private List<string[]> _data;

    private List<double> _fmtData;

    // Chamar apenas uma vez, não tem pq ler o arquivo várias vezes.
    public void Load() {
        _data = File.ReadAllLines("H:/arquivo.txt").Select(
            // l = 43,01463032;    46,8918;      9,5;
            // output = ["43,01463032", "46,8918", "9,5"]
            l => l.Split(';').Select(v => v.Trim()).ToArray()
        ).ToList();

        _fmtData = _data.Select(l => double.Parse(l[0])).ToList();
    }

    public (int lineIndex, string valor)? SearchData(string input) {
        if (!double.TryParse(input, out double di)) {
            return null;
        }

        // Se o elemento for menor ou igual que o primeiro,
        // retornamos ele.
        if (di <= _fmtData[0]) {
            return (0, _data[0][2]);
        }

        // Se o elemento for maior ou igual que o último,
        // retornamos ele.
        if (di >= _fmtData[^1]) {
            return (_fmtData.Count - 1, _data[^1][2]);
        }

        // Retornamos o que tiver a menor diferença.
        var difs = _fmtData.Select(savedData => Math.Abs(savedData - di)).ToList();
        var idx = difs.IndexOf(difs.Min());

        return (idx, _data[idx][2]);
    }

    // Retorna somente a coluna 3.
    public string SearchDataValueOnly(string input) {
        if (!double.TryParse(input, out double di)) {
            return "";
        }

        // Se o elemento for menor ou igual que o primeiro,
        // retornamos ele.
        if (di <= _fmtData[0]) {
            return _data[0][2];
        }

        // Se o elemento for maior ou igual que o último,
        // retornamos ele.
        if (di >= _fmtData[^1]) {
            return _data[^1][2];
        }

        // Retornamos o que tiver a menor diferença.
        var difs = _fmtData.Select(savedData => Math.Abs(savedData - di)).ToList();
        var idx = difs.IndexOf(difs.Min());

        return _data[idx][2];
    }
}

My txt file:

43,01463032;    46,8918;      9,5;
60,65734978;    67,14495;     1,5;
88,88570093;    90,7425;      13;
113,5855082;    149,5044;     14,5;
141,6293991;    183,29985;    16;
242,3097816;    261,6327;     19;

App:

class Program
{
    static void Main(string[] args) {
        var lk = new Arquivo_Dados();
        lk.Load();
        
        var r = lk.SearchData("512,50");
        Console.WriteLine("Index: {0}; Valor: {1}", r?.lineIndex, r?.valor);
        
        var r = lk.SearchData("10,688");
        Console.WriteLine("Index: {0}; Valor: {1}", r?.lineIndex, r?.valor);
        
        var r = lk.SearchData("64,355");
        Console.WriteLine("Index: {0}; Valor: {1}", r?.lineIndex, r?.valor);
        
        var r = lk.SearchData("117,92");
        Console.WriteLine("Index: {0}; Valor: {1}", r?.lineIndex, r?.valor);
    }
}

Upshot:

Index: 5; Valor: 19
Index: 0; Valor: 9,5
Index: 1; Valor: 1,5
Index: 3; Valor: 14,5

Observing

As you will filter data in response to an event of a textbox, that is, event coming from the user, it would be good for you to implement some system debauch in the textbox where the user type, preventing the pc to explode.

Another point is that I put tuple as nullable, in case the user sends an invalid value, although there in my example I am not doing the check, it would be good for you to do.

Edit - Combobox

I added these two functions in the data file class:

public string[] ListarColuna3() {
    return _data.Select(d => d[2]).ToArray();
}

public string[] BuscarPelaColuna3(int index) {
    // return _data.Where(d => d[2] == input).FirstOrDefault();
    return _data[index];
}

In my form:

public Form1() {
    InitializeComponent();

    _arqDados = new Arquivo_Dados();
    _arqDados.Load();

    comboBox1.Items.AddRange(_arqDados.ListarColuna3());
}

private void comboBox1_SelectedIndexChanged(object sender, EventArgs e) {
    var linha = _arqDados.BuscarPelaColuna3(comboBox1.SelectedIndex);

    textBox1.Text = linha[0];
    textBox2.Text = linha[1];
}

That one comboBox1_SelectedIndexChanged is a Combobox event. You can add it from the window properties or via code: comboBox1.SelectedIndexChanged += comboBox1_SelectedIndexChanged;. As the name suggests, it will be called when the selected index is changed.

Upshot: