Format error when trying to run the program

Question

So, today I was trying to make an app in which the user enters the coordinates of their car and the app calculates the easiest way to reach a gas station before the fuel tank runs out. But when I wanted to test if the app displays the data which is stored in a .txt file, I get a System.FormatException error which I cannot solve. I have used this method many many times before and I am not sure what is the problem here.

The error occurs at the line:

int xcoor = int.Parse(s.Substring(k + 1));

Code:

int n = 10;

string[] cities = new string[n];
int[] x = new int[n];
int[] y = new int[n];
System.IO.StreamReader sr = new System.IO.StreamReader(
    @"..\..\CitiesGPS.txt", Encoding.GetEncoding(1250));
for (int i = 0; i < n; i++)
{
    string s = sr.ReadLine();
    int k = s.IndexOf(";");
    string city = s.Substring(0, k);
    cities[i] = city;
    int xcoor = int.Parse(s.Substring(k + 1));
    x[i] = xcoor;
    int k2 = s.IndexOf(";");
    int ycoor = int.Parse(s.Substring(k2 + 1));
    y[i] = ycoor;
}

sr.Close();
Console.WriteLine("Data in the file:");
for (int i = 0; i < n; i++)
{
    Console.WriteLine(cities[i] + ";" + x[i] + ";" + y[i]);
}

Data:

Nagyváros;150;30
Kisváros;250;300
TanyaBenzunkúttal;290;310
Szépváros;500;10
Alsóváros;250;0
Felsőváros;560;560
Középváros;300;300
FolyópartiVáros;380;400
HáromBenzinkutasváros;10;400
Nagyvárosbvezetőútja;380;230

Thanks in advance,

Blaise

Answer 1

You don't have any length on the middle Substring call, so it takes the rest of the line.

int xcoor = int.Parse(s.Substring(k + 1, /* missing length*/));

But, please use a CSV-parser. There is no reason to re-invent the wheel every time you need it.

EDIT I just noticed you're getting the same index of ";" into both k and k2, so it won't work at all. Again, use a CSV-parser.

EDIT 2 If you won't use a CSV-parser, here is a solution with Split as @ADyson suggests:

for (int i = 0; i < n; i++)
{
    var parts = sr.ReadLine().Split(";");
    string city = parts[0];
    cities[i] = city;
    int xcoor = int.Parse(parts[1]);
    x[i] = xcoor;
    int k2 = s.IndexOf(";");
    int ycoor = int.Parse(parts[2]);
    y[i] = ycoor;
}

Answer 2

Apart from the general advice to use a ready-made CSV / delmimited-file parser for this task, your own code is massively over-complicating the problem, and suffers from various logical flaws when trying to detect the location of the delimiters and calculate the correct lengths of the strings in between them.

It's much simpler to just use the String.Split method.

Also your onward data structure (consisting of separate arrays for cities, x coords and y coords) doesn't make much sense if you're intending to then match the co-ordinates to the location names - if you want to do that, keep the data together. A simple object structure would make it easier to work with later on. And lists are generally easier to work with than arrays, too.

Also for simplicity you should just read to the end of the file, not a specific number of lines.

Lastly, best practice with a disposable item like a StreamReader is to initialise it in conjunction with a using block to ensure it's properly disposed afterwards (see StreamReader documentation examples.

e.g.

public class LocationData
{
  public string Name {get; set;}
  public int X {get; set;}
  public int Y {get; set;}
}

and then

using (System.IO.StreamReader sr = new new System.IO.StreamReader(@"..\..\CitiesGPS.txt", Encoding.GetEncoding(1250)))
{
  List<LocationData> locationList = new List<LocationData>();

  while ((s = sr.ReadLine()) != null)
  {
    string[] data = s.Split(';');
    LocationData loc = new LocationData()
    {
      Name = data[0],
      X = int.Parse(data[1]),
      Y = int.Parse(data[2])
    };
    locationList.Add(loc);
  }
}

foreach (LocationData loc in locationList)
{
    Console.WriteLine(loc.Name + ";" + loc.X + ";" + loc.Y);
}

P.S. Super-simple demo of processing a single row using string.split: https://dotnetfiddle.net/vGXu2O

Answer 3

The fail is with the substring in the line

int xcoor = int.Parse(s.Substring(k + 1));

You are trying to parse to int the value 150;30. And obviously it can't be parsed as a number.

I recommend split every line by ; to get the values for each position.

You can do this inside for loop:

string[] line = s.Split(";");
var city = line[0];
var xcoor = int.Parse(line[1]);
var ycoor = int.Parse(line[2]);
cities[i] = city;
x[i] = xcoor;
y[i] = ycoor;

Edit to add how it works using substring().

Substring method takes two arguments:

1st: Is the position where start.
2nd: Is how many positions more do you want to get.

So, the solution is get the ondex of all ; (I've used a lambda expression) and then use substring in a correct way.

That is: Saying the program to start where a semicolon has been found and end as many position as there exists until the next semicolon.

var indexes = Regex.Matches(s, ";").Cast<Match>().Select(m => m.Index).ToList();
var city = s.Substring(0,indexes[0]);
var xcoor = s.Substring(indexes[0]+1,(indexes[1]-indexes[0])-1);
var ycoor = s.Substring(indexes[1]+1, (s.Length-indexes[1])-1);
cities[i] = city;
x[i] = int.Parse(xcoor);
y[i] = int.Parse(ycoor);

With this code, you can see the position where to start and 'cut' the substring.