How to get specific text from a txt file in C#?

Question

I’m a layman, still taking the first steps in programming and C# and I’m having trouble solving a problem.

I would like to search a specific information in a txt file with the following lines:

Nodal force point

15  25  30

20  35  13

25  85  25


Nodal Moment point

23  58  6

6   4   5   

3   2   1

Nodal displacements point

25  1   5

2   5   4

6   4   5

Well, I need to identify the "Nodal Moment point" and store the second row value (In that case, the 4).

Note: It will not necessarily be 4, since they are randomly generated values. Ah, the file will always follow this pattern (Each title will have 3 rows of data, it will always have a blank row and the columns are separated by 2 spaces)

I am using the following code to locate the part of the file that contains the "Nodal Moment point":

var valor = File.ReadAllLines("NomeDoArquivo.txt")
                .Where(l=>l.StartsWith("Nodal Moment"))

However, I don’t know how to find the second value of the second line and store in the variable.

I thank you in advance for your help.

Answer 1

class Program
{
    static void Main(string[] args)
    {
        string arquivo = @"C:\temp\teste.txt";

        if(File.Exists(arquivo))
        {
                try
                {
                    string[] listTxt = File.ReadAllLines(arquivo);
                    var strList = listTxt[13];
                    var values = strList.Split("  ");
                    var result = values[1];
                }
            catch (Exception ex)
            {
                throw ex;
            }
        }

        Console.ReadKey();
    }
}

Answer 2

The algorithm is simple:

• File.ReadAllLines("file.txt"): Read the text file.
• SkipWhile(l => l != "Nodal Moment point"): Discard all lines until you find the string "Nodal Moment point".
• Except(new string[]{""}): Remove all empty lines.
• Skip(1): Discard the line containing the string "Nodal Moment point".
• TakeWhile(l => Char.IsNumber(l[0])): Pick up the lines while the first character is numeric and discard all lines including and after finding the first line whose first character is not numeric.
• Select((l,_) => l.Split(" ", StringSplitOptions.RemoveEmptyEntries)): For the remaining lines to explode them into spaces in string arrays discarding empty strings.
• ToArray(): Join the result in a row-by-column array.

^{Remembering that arrays in C# begin at index 0.
So if you want the third element of the first line data[0][2].}

using System;
using System.IO;
using System.Linq;

class MainClass {
  public static void Main (string[] args) {
    var data = File.ReadAllLines("file.txt")       
       .SkipWhile(l => l != "Nodal Moment point")
       .Except(new string[]{""})
       .Skip(1)
       .TakeWhile(l => Char.IsNumber(l[0]))
       .Select((l,_) => l.Split(" ", StringSplitOptions.RemoveEmptyEntries))
       .ToArray();
    Console.WriteLine(data[1][1]);    //4
  }
}

^{Test the example on Repl.it}

Visualization of what each function does:

• File.ReadAllLines("file.txt")

Nodal force point

15  25  30

20  35  13

25  85  25


Nodal Moment point

23  58  6

6   4   5   

3   2   1

Nodal displacements point

25  1   5

2   5   4

6   4   5

• SkipWhile(l => l != "Nodal Moment point")

Nodal Moment point

23  58  6

6   4   5   

3   2   1

Nodal displacements point

25  1   5

2   5   4

6   4   5

• Except(new string[]{""})

Nodal Moment point
23  58  6
6   4   5
3   2   1
Nodal displacements point
25  1   5
2   5   4
6   4   5

• Skip(1)

23  58  6
6   4   5
3   2   1
Nodal displacements point
25  1   5
2   5   4
6   4   5

• TakeWhile(l => Char.IsNumber(l[0]))

23  58  6
6   4   5
3   2   1

• Select((l,_) => l.Split(" ", StringSplitOptions.RemoveEmptyEntries))

Array<String>["23","58","6"]
Array<String>["6","4","5"]
Array<String>["3","2","1"]

• ToArray();

data = [["23","58","6"], ["6","4","5"], ["3","2","1"]]

References:

• File.ReadAllLines()
• Enumerable.SkipWhile()
• Enumerable.Except()
• Enumerable.Skip()
• Enumerable.TakeWhile()
• Enumerable.Select()
• Enumerable.ToArray()
• Char.IsNumber()
• String.Split()
• System.Linq
• System.IO