CODEWITHSUNDEEP
c#arrays
miraco
miraco

Reputation: 418

string.Join(string, string[]) returns "System.String[]"

I need some help. I have a method that should output a txt file with the contents of a list(each item on a line). The list items are string arrays. The problem is that when I call string.Join it returns the literal string "System.String[]" instead of the actual concatenated string. I watched it in the debugger and the list and its arrays have the correct strings. Any idea how I can get the actual string so it can be written in the txt file?

Here is my code :

 public void myMethod()
    {
        List<Array> list = new List<Array>();
        for (int i = 0; i < myGrid.Rows.Count; i++)
        {
            string[] linie = new string[3];
            linie[0] = myGrid.Rows[i].Cells[1].Value.ToString();
            linie[1] = myGrid.Rows[i].Cells[3].Value.ToString();
            linie[2] = myGrid.Rows[i].Cells[2].Value.ToString();

            {
                list.Add(linie);
            }
        }
        string path = "S:\\file.txt";
        StreamWriter file = new System.IO.StreamWriter(path);
        foreach (Array x in list)
        {
            string s = string.Join(",", x);
            file.WriteLine(s);
        }
            file.Close();
  }

Upvotes: 6

Views: 4511

Answers (3)

D Stanley
D Stanley

Reputation: 152566

Here's the reason you're getting those results:

The overloads for string.Join are:

Join(string, params object[])
Join(string, params string[])
Join(string, params string[], int, int)
Join(string, IEnumerable<string>)
Join<T>(string, IEnumerable<string>)

Since your second parameter to string.Join is an untyped Array, which is neither a string[] nor an IEnumerable<T>, the "best" overload is Join(string, params object[]), with the Array treated an an object[] with a single value - the Array (not an object[] with several string or object values). So Join calls ToString() on the Array, which returns System.String[] since that is the actula type of the Array.

There are multiple ways to fix it, but to me the cleanest is to use List<string[]> instead of List<Array> since you only ever store strings in the array. That way the overload 'Join(string, string[])` will be called which gives you the results you expect:

public void myMethod()
{
    List<string[]> list = new List<string[]>();
    for (int i = 0; i < myGrid.Rows.Count; i++)
    {
        string[] linie = new string[3];
        linie[0] = myGrid.Rows[i].Cells[1].Value.ToString();
        linie[1] = myGrid.Rows[i].Cells[3].Value.ToString();
        linie[2] = myGrid.Rows[i].Cells[2].Value.ToString();

        {
            list.Add(linie);
        }
    }
    string path = "S:\\file.txt";
    StreamWriter file = new System.IO.StreamWriter(path);
    foreach (string[] x in list)
    {
        string s = string.Join(",", x);
        file.WriteLine(s);
    }
        file.Close();
}

Upvotes: 2

Dustin Kingen
Dustin Kingen

Reputation: 21245

Change the type of

List<Array> list = new List<Array>();

to

List<string[]> list = new List<string[]>();

You can use File.WriteAllLines.

string[] contents = list.Select(a => string.Join(",", a)).ToArray();

File.WriteAllLines(path, contents);

Upvotes: 3

SLaks
SLaks

Reputation: 887489

string.Join() takes a params object[].

When you pass a variable of compile-time type Array, it interprets that as a single item in the array, and it ends up passing new object[] { yourArray }.
It then calls ToString() on the single item, which returns the type name (since arrays do not override ToString().

To fix that, you need to change Array to any strongly-typed collection type (string[], object[], or IEnumerable<string>).
It will then pass the array itself to Join(), instead of assuming it's a single parameter in the paramarray.

Upvotes: 19

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