Trim all chars off file name after first "_"

Question

I'd like to trim these purchase order file names (a few examples below) so that everything after the first "_" is omitted.

INCOLOR_fc06_NEW.pdf Keep: INCOLOR (write this to db as the VendorID) Remove: _fc08_NEW.pdf

NORTHSTAR_sc09.xls Keep: NORTHSTAR (write this to db as the VendorID) Remove: _sc09.xls

Our scenario: The managers are uploading these files to our Intranet web server, to make them available to download/view ect. I'm using Brettles NeatUpload, and for each file uploaded, am writing the files attributes into the PO table (sql 2000). The first part of the file name will be written to the DB as a VendorID.

The naming convention for these files is consistent in that the the first part of the file is always the vendor name (or Vendor ID) followed by an "_" then other unpredictable chars used to identify the type of Purchase Order then the file extention - which is consistently either .xls, .XLS, .PDF, or .pdf.

I tried TrimEnd - but the array of chars that you have to provide ends up being long and can conflict with the part of the file name I want to keep. I have a feeling I'm not using TrimEnd properly.

What is the best way to use string.TrimEnd (or any other string manipulation in C#) that will strip off all chars after the first "_" ?

Answer 1

String s = "INCOLOR_fc06_NEW.pdf";
int index = s.IndexOf("_");

return index >= 0 ? s.Substring(0,index) : s;

Answer 2

public string StripOffStuff(string sInput)
{
  int iIndex = sInput.IndexOf("_");

  return (iIndex > 0) ? sInput.Substring(0, iIndex) : sInput;
}

// Call it like:
string sNewString = StripOffStuff("INCOLOR_fc06_NEW.pdf");

Answer 3

TrimEnd removes white spaces and punctuation marks at the end of the String, it won't help you here. Read more about TrimEnd here: http://msdn.microsoft.com/en-us/library/system.string.trimend.aspx

Bnaffas code (with a small tweak):

String fileName = "INCOLOR_fc06_NEW.pdf";
int index = fileName.IndexOf("_");

return index >= 0 ? fileName.Substring(0, index) : fileName;

If you want to do something with the other parts, you could use a Split

string fileName = "INCOLOR_fc06_NEW.pdf";
string[] parts = fileName.Split('_');

Answer 4

I'll probably offend the anti-regex lobby, but here I go (ducking):

string stripped = Regex.Replace(filename, @"(?<=[^_]*)_.*",String.Empty);

This code will strip all extra characters after the first '_', unless there is no '_' in the string (then it will just return the original string).

It's one line of code. It's slower than the more elaborate IndexOf() algorithm, but when used in a non-performance-sensitive part of the code, it's a good solution.

Get your flame-throwers out...

Answer 5

I would go with the SubString approach but to round out the available solutions here's a LINQ approach just for fun:

string filename = "INCOLOR_fc06_NEW.pdf";
string result = new string(filename.TakeWhile(c => c != '_').ToArray());

It'll return the original string if no underscore is found.

Answer 6

To go with all the "alternative" solutions, here's the second one that I thought of (after substring):

string filename = "INCOLOR_fc06_NEW.pdf";
string stripped = filename.Split('_')[0];