How can I replace the same name of a file using regex but in another format?

Question

I am new in programming and not so good about regex. I wish to load / read a csv File and then save in a txt File using the same name of csv File. I will give an example.

D:\Project\File\xxx.csv

After I load this file, I want to get the name "xxx" and save it in a txt file:

D:\Project\File\xxx.txt

Or maybe in another folder, for example:

D:\Project\Specifications\PersonInfo.csv

save to

D:\Project\DataBank\PersonInfo.txt

Answer 1

This can be accomplished in many ways.

Maybe what you're lacking is knowledge of the System.IO.Path class (MSDN article here).

For instance changing the extension could be accomplished like so:

string originalFilePath = @"D:\Project\File\xxx.csv";
string newFilePath = Path.ChangeExtension(originalFilePath, ".txt");

Note: You need to explicitate the leading dot (".") for the extension.

Here's some "Path algebra" fun you could combine to create your desired effects:

string originalFilePath = @"D:\Project\File\xxx.csv";
string thePath = Path.GetDirectoryName(originalFilePath);
// will be @"D:\Project\File"

string filename = Path.GetFileName(originalFilePath);
// will be "xxx.csv"

string fileNameWithoutExtension = Path.GetFileNameWithoutExtension(originalFilePath);
// will be "xxx"

string recombinedFilePath = Path.Combine( @"D:\OtherFolder", "somethingElse.txt" );
// will be @"D:\OtherFolder\somethingElse.txt"

Note: Path.Combine knows how to handle extra/missing leading/trailing backslashes.

For example:

• Path.Combine(@"D:\MyFolder1", @"MyFolder2\MyFile.txt")
• Path.Combine(@"D:\MyFolder1\", @"MyFolder2\MyFile.txt")
• Path.Combine(@"D:\MyFolder1", @"\MyFolder2\MyFile.txt")
• Path.Combine(@"D:\MyFolder1\", @"\MyFolder2\MyFile.txt")

will all yield the same result: @"D:\MyFolder1\MyFolder2\MyFile.txt"

Answer 2

You do not need regex for that, because .NET provides a System.IO.Path class for dealing specifically with file name manipulations.

For example, to replace .csv with .txt you can use this call:

var csvPath = @"D:\Project\File\xxx.csv";
var txtPath = Path.Combine(
    Path.GetDirectoryName(csvPath)
,   Path.GetFileNameWithoutExtension(csvPath)+".txt"
);

You use a similar trick to replace other parts of the file path. Here is how you change the name of the top directory:

var csvPath = @"D:\Project\Specifications\xxx.csv";
var txtPath = Path.Combine(
    Path.GetDirectoryName(Path.GetDirectoryName(csvPath))
,   "DataBank"
,   Path.GetFileNameWithoutExtension(csvPath)+".txt"
);

Answer 3

You don't need Regex.

You can use Path.GetFileName or Path.GetFileNameWithoutExtension:

string fileName = Path.GetFileNameWithoutExtension("D:\Project\Specifications\PersonInfo.csv");

Answer 4

If you want to use regex for this, this regex will get the part you want:

([^\\]+)\.[^.\\]+$

The first group (in the parentheses) matches one or more characters (as many as possible) which is not a backslash. Then there need to be a literal dot. Then one or more characters (as many as possible) that are not a dot or backslash, then the end of the string. The group captures the wanted part.