using foreach to store names of one array in another in c#

Question

Now I have a directory with bunch files with format of name like "EXT2-401-B-140422-1540-1542.mp4", within which the "140422" part indicates the date. Now assume that this bunch of files have the dates like 140421, 140422, 140423...(for every date there are couple of files). Now I shall sort these files according to their dates, so I'd like to know how could I get these names (140421,140422,etc). I tried like this:

directory = new DirectoryInfo(camera_dir);    
string[] date = new string[directory.GetFiles().Length];
foreach (FileInfo file in directory.GetFiles())
{ 
    foreach(string name in date)
    {
        name = file.Name.Substring(11, 6);
    }
}

And the error message is that I can't assign to name. So anybody could help?

Answer 1

You can use LINQ to simplify this a bit.

To get filenames only, you simply need to project each FileInfo into a string:

var dates = directory
    .EnumerateFiles("*.mp4")
    .Select(f => f.Name)
    .ToArray();

To get an ordered list, you also need to use OrderBy and specify the value to be used for ordering:

var dates = directory
    .EnumerateFiles("*.mp4")
    .Select(f => f.Name)
    .OrderBy(f => f.Substring(11, 6)) // this will throw if string is too short
    .ToArray();

You should also probably add some validation to prevent exceptions when filenames are not formatted properly. The least you can do is check if the string is long enough to have these 6 characters extracted:

var dates = directory
    .EnumerateFiles("*.mp4")
    .Select(f => f.Name)
    .Where(f => f.Length >= 17) // check if there are enough characters
    .OrderBy(f => f.Substring(11, 6))
    .ToArray();

Answer 2

try this:

    var files = directory.GetFiles();
    string[] dates = new string[files.Length];
    for(int i = 0; i < files.Length; i++)
    { 
        dates[i] = files[i].Name.Substring(11, 6);
    }

Answer 3

In fact you are asking two questions.

1. You cannot assign a variable from the foreach. Create a new one to store the name in.

2. For the second part, how to extract it: use this regex:

   string s = Regex.Replace(file.Name, @"(.*?)\-(.*?)\-(.*?)\-(.*?)\-(.*)", "$4");
   

   The ? makes the regex non-greedy, meaning that this expression will find the text after the third dash.

Answer 4

directory = new DirectoryInfo(camera_dir);    
string[] date = new string[directory.GetFiles().Length];
int i=0;
foreach (FileInfo file in directory.GetFiles())
{ 
    name[i] = file.Name.Substring(11, 6);
    i++;
}

Answer 5

I would be doing something like creating a class for the file name (if they are all the same structure) then splitting them out (apologies for reworking the entire code, also what the other guys are saying is something worth noting about foreach's not begin able to modify the set)...

public class MyFile 
{
    // EXT2-401-B-140422-1540-1542.mp4
    public string part1 { get; set;}
    public string part2 { get; set;}
    public string part3 { get; set;}
    public string date { get; set;}
    public string part5 { get; set;}
    public string part6 { get; set;}

    void MyFile(string fileName)
    {
        string[] parts = fileName.split('-');

        part1 = parts[0];
        part2 = parts[1];
        part3 = parts[2];
        date  = parts[3];
        part5 = parts[4];
        part6 = parts[5];
    }
}

then you can loop through...

directory = new DirectoryInfo(camera_dir);    

List<MyFile> myFiles = new List<MyFile>();

foreach (FileInfo file in directory.GetFiles())
{    
   myFiles.Add(new MyFile(file.Name));
}

Then you can sort, select, "blah" on any of the files using linq...

EDIT:

Additionally, if your previous code worked, you would end up with the date array being full of one date because you are trying to set the name (being each element in the array) to the current file name for the length of the array every single iteration of the directory.GetFiles() array.

Name the 'parts' something useful to you.