Hi. I would like to convert empty string "" to zero in C#. The data is stored in (string) arrays. There is jagged array which contains all 5 string arrays. Could someone help?

// Jagged array intialization
string[][] all_prices = new string[5][];
all_prices[0] = nordpool;
all_prices[1] = tvh;
all_prices[2] = ttoist;
all_prices[3] = tarj1v;
all_prices[4] = tarj2v;

There can be some empty ("") values and I want convert them to zero.

What exactly do you mean? Something like this?

string.IsNullOrEmpty(all_prices[0][0]) ? 0 : int.Parse(all_prices[0][0]);

That example just returns 0 if it's null or empty, otherwise it parses the string (you could use float/double/decimal instead), but I'm not sure if that's what you're trying to do... If it is, could I ask why numeric values are being stored as strings?

I am using streamreader and first I read a line to string array, then split values separated by : and later I make decimal type list and add prices to list. For example, there can be line like this:

:2.20:2.20:2.20:2.20|7.18:7.18:7.18:7.18:7.18|6.95:6.95:6.95:6.95:6.95|6.98:6.98:6.98:6.98:6.98|6.86:6.86:6.86:6.86:6.86

First value is "" and I would like to convert its value to zero. Now I get "formatexception" when running the program. I don't know how to make a loop which check "" values and convert them.

Ah, ok. So you would use something similar to what I put above.

for(...)
{
    ...
    double d = all_prices[i1][i2] == string.Empty ? 0.0 : double.Parse(all_prices[i1][i2]);
    ...
}

The ? and : operators are just shorthand for:

for(...)
{
    ...
    double d;
    if(all_prices[i1][i2] == string.Empty)
        d = 0.0;
    else
        d = double.Parse(all_prices[i1][i2]);
    ...
}

You could use either one, it doesn't really matter. Also, string.Empty is equivalent to "", it doesn't really matter which one you use. Without your source code I can't really make any specific recommendations, but you should be able to use this as a starting point.

I don't know what I should do with d variable. Here is more code...

                using (StreamReader reader = new StreamReader(e.Result))
                {
                    List<string> line = new List<string>();

                    while (!reader.EndOfStream)
                    {
                        line.Add(reader.ReadLine());
                        //MessageBox.Show(line[0]);
                    }

                    reader.Close();

                    string[] section = line[0].Split('|');
                    string[] nordpool = section[0].Split(':');
                    string[] tvh = section[1].Split(':');
                    string[] ttoist = section[2].Split(':');
                    string[] tarj1v = section[3].Split(':');
                    string[] tarj2v = section[4].Split(':');

                    // Jagged array
                    string[][] all_prices = new string[5][];
                    all_prices[0] = nordpool;
                    all_prices[1] = tvh;
                    all_prices[2] = ttoist;
                    all_prices[3] = tarj1v;
                    all_prices[4] = tarj2v;

                    for (int i = 0; i < all_prices.Count(); i++)
                    {
                        if (all_prices[i].Contains(""))
                        {
                            // Dont know what to do
                        }
                    }

                    List<double> list_nordpool = new List<double>();
                    List<double> list_tvh = new List<double>();
                    List<double> list_ttoist = new List<double>();
                    List<double> list_tarj1v = new List<double>();
                    List<double> list_tarj2v = new List<double>();

                    for (int j = 0; j < number; j++)
                    {
                        list_nordpool.Add(double.Parse(all_prices[0][j]));
                        list_tvh.Add(double.Parse(all_prices[1][j]));
                        list_ttoist.Add(double.Parse(all_prices[2][j]));
                        list_tarj1v.Add(double.Parse(all_prices[3][j]));
                        list_tarj2v.Add(double.Parse(all_prices[4][j]));
                    }

                    ...

Change this:

for (int j = 0; j < number; j++)
{
    list_nordpool.Add(double.Parse(all_prices[0][j]));
    list_tvh.Add(double.Parse(all_prices[1][j]));
    list_ttoist.Add(double.Parse(all_prices[2][j]));
    list_tarj1v.Add(double.Parse(all_prices[3][j]));
    list_tarj2v.Add(double.Parse(all_prices[4][j]));
}

to this:

for (int j = 0; j < number; j++)
{
    list_nordpool.Add(all_prices[0][j] == "" ? 0.0 : double.Parse(all_prices[0][j]));
    list_tvh.Add(all_prices[1][j] == "" ? 0.0 : double.Parse(all_prices[1][j]));
    list_ttoist.Add(all_prices[2][j] == "" ? 0.0 : double.Parse(all_prices[2][j]));
    list_tarj1v.Add(all_prices[3][j] == "" ? 0.0 : double.Parse(all_prices[3][j]));
    list_tarj2v.Add(all_prices[4][j] == "" ? 0.0 : double.Parse(all_prices[4][j]));
}

This compares the string to the empty string. If they are equal, it passes 0 into the Add() method. Otherwise, it passes the return value from double.Parse() (but does not execute Parse() unless it has to).