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Get File Extension C#

I have a dropdown with list of file names. When a file name is selected in the dropdown I do the following
string filename = ddl.SelectedItem.Text;
string path = "F:\\WorkingCopy\\files\\" + filename +".docx";
DownloadFile(path,filename);
In the file folder files may contain any extension . Since i have hard coded ".docx" in string path everything works fine. But I need to get the extension of the file name with the ddl.SelectedItem.Text alone. Can you tell me how to do this?
Things I have
1.) File name without extension in
string filename = ddl.SelectedItem.Text;
2.) Path where the file is located
string path = "F:\\WorkingCopy\\files\\" + filename
I am trying to get the file extension with these . Can any one suggest on this?

You can use Directory.EnumerateFiles() like this:
string path = "F:\\WorkingCopy\\files\\";
string filename = ddl.SelectedItem.Text;
string existingFile = Directory.EnumerateFiles(path, filename + ".*").FirstOrDefault();
if (!string.IsNullOrEmpty(existingFile))
Console.WriteLine("Extension is: " + Path.GetExtension(existingFile));
Directory.EnumerateFiles searches the path for files like filename.*. Path.GetExtension() returns the extension of the found file.
In general, I prefer to use EnumerateFiles() instead of GetFiles because it returns an IEnumerable<string> instead string[]. This suggests that it only returns the matching files as needed instead searching all matching files at once. (This doesn't really matter in your case, just a general note).

Use the Directory.GetFiles() method. Something like this
string[] files = Directory.GetFiles("F:\\WorkingCopy\\files\\", filename+".*");
This should get you an array of filenames with the same filename but different extensions. If you have only one, then you can always use the first one.

You can use Directory.GetFiles Method:
string result = Directory.GetFiles(path, filename + ".*").FirstOrDefault();
see here
here " * " is the WildCard and will search for the Filename starts with YourFileName.

you can achieve that with followed by line
try
{
var extensions = new List<string>();
var files = Directory.GetFiles("F:\\WorkingCopy\\files\\", filename + ".*", System.IO.SearchOption.TopDirectoryOnly);
foreach (var tmpfile in files)
extensions.Add(Path.GetExtension(tmpfile));
}
catch (Exception ex)
{
throw ex;
}
will this help you?

You can simply split them by dot, For example, try this code
string folder = #"F:\\WorkingCopy\\files\\";
var files = System.IO.Directory.GetFiles(folder, filename + ".*");
if (files.Any())
{
string ext = System.IO.Path.GetExtension(files.First()).Substring(1);
}
This code gives me result that the extension for this is txt file.

How to get the substring after a given string

I'm new to C# and struggle with string parsing. I have a string like this:
C:\User\Max\Pictures\
And I got multiple file paths:
C:\User\Max\Pictures\car.jpg
C:\User\Max\Pictures\trains\train.jpg
How can I strip the base path from those file paths to get:
car.jpg
trains\train.jpg
Something like this failed:
string path = "C:\\User\\Max\\Pictures\\";
string file = "C:\\User\\Max\\Pictures\\trains\\train.jpg";
string newfile = file.Substring(file.IndexOf(path));

You want to get the substring of file after the length of path:
string newfile = file.Substring(path.Length);
Note that it's a good idea to use Path methods like Path.GetFileName() when dealing with file paths (though it's not good applyable to the "train" example).

The other answer would be to replace your path with an empty string :
string filePath = file.Replace(path, "");

There are special classes to handle filepaths
var filePath = new FileInfo("dd");
In filePath.Name is the filename of the file whitout directory
So for your scenario you want to strip base dir. So you can do this
var filePath = new FileInfo(#"c:\temp\train\test.xml");
var dir = filePath.FullName.Replace(#"c:\temp", String.Empty);

How to get the second to last directory in a path string in C#

For example,
string path = #"C:\User\Desktop\Drop\images\";
I need to get only #"C:\User\Desktop\Drop\
Is there any easy way of doing this?

You can use the Path and Directory classes:
DirectoryInfo parentDir = Directory.GetParent(Path.GetDirectoryName(path));
string parent = parentDir.FullName;
Note that you would get a different result if the path doesn't end with the directory-separator char \. Then images would be understood as filename and not as directory.
You can also use a subsequent call of Path.GetDirectoryName
string parent = Path.GetDirectoryName(Path.GetDirectoryName(path));
This behaviour is documented here:
Because the returned path does not include the DirectorySeparatorChar
or AltDirectorySeparatorChar, passing the returned path back into the
GetDirectoryName method will result in the truncation of one folder
level per subsequent call on the result string. For example, passing
the path "C:\Directory\SubDirectory\test.txt" into the
GetDirectoryName method will return "C:\Directory\SubDirectory".
Passing that string, "C:\Directory\SubDirectory", into
GetDirectoryName will result in "C:\Directory".

This will return "C:\User\Desktop\Drop\" e.g. everything but the last subdir
string path = #"C:\User\Desktop\Drop\images";
string sub = path.Substring(0, path.LastIndexOf(#"\") + 1);
Another solution if you have a trailing slash:
string path = #"C:\User\Desktop\Drop\images\";
var splitedPath = path.Split('\\');
var output = String.Join(#"\", splitedPath.Take(splitedPath.Length - 2));

var parent = "";
If(path.EndsWith(System.IO.Path.DirectorySeparatorChar) || path.EndsWith(System.IO.Path.AltDirectorySeparatorChar))
{
parent = Path.GetDirectoryName(Path.GetDirectoryName(path));
parent = Directory.GetParent(Path.GetDirectoryName(path)).FullName;
}
else
parent = Path.GetDirectoryName(path);
As i commented GetDirectoryName is self collapsing it returns path without tralling slash - allowing to get next directory.Using Directory.GetParent for then clouse is also valid.

Short Answer :)
path = Directory.GetParent(Directory.GetParent(path)).ToString();

Example on the bottom of the page probably will help:
http://msdn.microsoft.com/en-us/library/system.io.path.getdirectoryname(v=vs.110).aspx

using System;
namespace Programs
{
public class Program
{
public static void Main(string[] args)
{
string inputText = #"C:\User\Desktop\Drop\images\";
Console.WriteLine(inputText.Substring(0, 21));
}
}
}
Output:
C:\User\Desktop\Drop\

There is probably some simple way to do this using the File or Path classes, but you could also solve it by doing something like this (Note: not tested):
string fullPath = "C:\User\Desktop\Drop\images\";
string[] allDirs = fullPath.split(System.IO.Path.PathSeparator);
string lastDir = allDirs[(allDirs.length - 1)];
string secondToLastDir= allDirs[(allDirs.length - 2)];
// etc...

Get full path without filename from path that includes filename

Is there anything built into System.IO.Path that gives me just the filepath?
For example, if I have a string
#"c:\webserver\public\myCompany\configs\promo.xml",
is there any BCL method that will give me
"c:\webserver\public\myCompany\configs\"?

Path.GetDirectoryName()... but you need to know that the path you are passing to it does contain a file name; it simply removes the final bit from the path, whether it is a file name or directory name (it actually has no idea which).
You could validate first by testing File.Exists() and/or Directory.Exists() on your path first to see if you need to call Path.GetDirectoryName

Console.WriteLine(Path.GetDirectoryName(#"C:\hello\my\dear\world.hm"));

Path.GetDirectoryName() returns the directory name, so for what you want (with the trailing reverse solidus character) you could call Path.GetDirectoryName(filePath) + Path.DirectorySeparatorChar.

string fileAndPath = #"c:\webserver\public\myCompany\configs\promo.xml";
string currentDirectory = Path.GetDirectoryName(fileAndPath);
string fullPathOnly = Path.GetFullPath(currentDirectory);
currentDirectory: c:\webserver\public\myCompany\configs
fullPathOnly: c:\webserver\public\myCompany\configs

Use GetParent() as shown, works nicely. Add error checking as you need.
var fn = openFileDialogSapTable.FileName;
var currentPath = Path.GetFullPath( fn );
currentPath = Directory.GetParent(currentPath).FullName;

I used this and it works well:
string[] filePaths = Directory.GetFiles(Path.GetDirectoryName(dialog.FileName));
foreach (string file in filePaths)
{
if (comboBox1.SelectedItem.ToString() == "")
{
if (file.Contains("c"))
{
comboBox2.Items.Add(Path.GetFileName(file));
}
}
}

Do I use a regular expression on this file path?

I have to strip a file path and get the parent folder.
Say my path is
\\ServerA\FolderA\FolderB\File.jpg
I need to get
File Name = File.jog
Folder it resides in = FolderB
And parent folder = FolderA
I always have to go 2 levels up from where the file resides.
Is there an easier way or is a regular expression the way to go?

FileInfo is your friend:
using System;
using System.IO;
class Test
{
static void Main(string[] args)
{
string file = #"\\ServerA\FolderA\FolderB\File.jpg";
FileInfo fi = new FileInfo(file);
Console.WriteLine(fi.Name); // Prints File.jpg
Console.WriteLine(fi.Directory.Name); // Prints FolderB
Console.WriteLine(fi.Directory.Parent.Name); // Prints FolderA
}
}

string fileName = System.IO.Path.GetFileName(path);
string parent = System.IO.Path.GetDirectoryName(path);
string parentParent = System.IO.Directory.GetParent(parent);

Check out the Directory class (better choice than DirectoryInfo in this case). It does everything you need. You should not use a regex or any other parsing technique.

var fi = new FileInfo(#"\\ServerA\FolderA\FolderB\File.jpg");
fi.Name
fi.Directory.Name
fi.Directory.Parent.Name

You have a few options to do this actually which use actual .net objects instead of regex.
You can use the FileInfo:
FileInfo fileInfo = new FileInfo(#"\\ServerA\FolderA\FolderB\File.jpg");
fileInfo.Name //will give you the file name;
DirectoryInfo directory = fileInfo.Directory; //will give you the parent folder of the file (FolderB);
directory.Parent; //will give you this directories parent folder (FolderA)

If you know for sure that you are always dealing with a file and two directories, try using split:
string s = #"\\ServerA\FolderA\FolderB\File.jpg";
string[] parts = s.Split('\'); // might need '\\'
string file = parts[parts.Length];
string parentDir = parts[parts.Length - 1];
string grandParentDir = parts[parts.Length - 2];