We Keep Coding

Split a string at 2 points

I have a file called file_test1.txt and I want to extract just test1 from the name and place it in a string. Whats the best way of doing this?
E.g.
string fullfile = #"C:\file_test1.txt";
string section = [test1] from fullfile; // <- expected result
I want to be able to split on 'file_' and '.txt' as the 'test1' section could be larger or smaller however the 'file_' and '.txt' will always be the same.

Try Path.GetFileNameWithoutExtension(fullfile).Substring(5) (or Substring("TEMPLATE_PREFIX".Length))

You can try spilt
var test = Path.GetFileNameWithoutExtension(fullfile).split('_')[1];

Try following
string fullfile = #"C:\file_test1.txt";
var name = fullfile.Substring(8,fullfile.Length-12)
As c:\file_ and .txt are fixed, You can take Substring starting at index 8 (skip leading name), upto length of total string length - 12 (12 => length of leading name, and trailing extension)

Thought I'd give a solution that uses Split and handles files with multiple underscores:
string.Join("_", Path.GetFileNameWithoutExtension(file).Split('_').Skip(1));

String.Split() works quite well for my uses:
http://msdn.microsoft.com/en-us/library/b873y76a.aspx

Obviously many ways to accomplish this. Here's yet another approach:
string fullfile = #"C:\file_test1.txt";
int index1 = fullfile.LastIndexOf("file_");
if (index1 != -1)
{
int index2 = fullfile.IndexOf(".", index1);
if (index2 != -1)
{
string section = fullfile.Substring(index1 + 5, index2 - index1 - 5);
}
}

You could also get "test1", or any subsequent filename (assuming your file naming convention remains constant!) using this regular expression:
var defaultRegex = new Regex(#"(?<=_).*(?=.txt)");
var matches = defaultRegex.Matches(fullfile);
var match = matches[0].Value;
The regular expression:
(?<=_).*(?=.txt)
uses positive look behind to find text preceded by '_', and also positive lookahead to find text which has '.txt' ahead of it.

How to get middle part of string between definite symbols?

I have strings like:
"d:\tmp\abc_list.csv"
"d:\tmp\xyzx_list.csv"
"d:\tmp\qwert_list.csv"
I need to take first part of filename: abx,xyzc, qwert. I do it now as:
string name = filename.Substring(filename.LastIndexOf('\\') + 1 , filename.IndexOf('_') - filename.LastIndexOf('\\') - 1);
I feel there should be easier and nicer way to do it. What is it?

Use the Path class:
string fullPath = #"d:\tmp\abc_list.csv";
string fileNameWOE = Path.GetFileNameWithoutExtension(fullPath);
string firstToken = fileNameWOE.Split('_').First();

Your solution is nice, but it is going to break if another part of the file name, say, part of its directory path, has an underscore. You should change it slightly to avoid this problem:
int pos = filename.LastIndexOf('\\') + 1;
string name = filename.Substring(pos , filename.IndexOf('_', pos) - pos);
When your solution is nice, robust, and easy to understand, there's no reason to go for a shorter solution. Of course you can use regular expression, but the resulting one-line solution is far less readable:
var res = Regex.Matches(s, #"(?<=\\)[^_\\]*(?=_[^\\]*$)")[0].Value;
Here is a demo of this solution on ideone.

you can use the Path class
and Path.GetFileNameWithoutExtension Method
http://msdn.microsoft.com/en-us/library/system.io.path.getfilenamewithoutextension.aspx

Something like this:
string str = #"d:\tmp\abc_list.csv";
// The preferred way to manipulate paths is to use the Path.* methods
string str2 = Path.GetFileNameWithoutExtension(str);
int ix = str2.LastIndexOf('_');
if (ix != -1)
{
str2 = str2.Remove(ix);
}

Getting substring between two separators in an arbitrary position

I have following string:
string source = "Test/Company/Business/Department/Logs.tvs/v1";
The / character is the separator between various elements in the string. I need to get the last two elements of the string. I have following code for this purpose. This works fine. Is there any faster/simpler code for this?
CODE
static void Main()
{
string component = String.Empty;
string version = String.Empty;
string source = "Test/Company/Business/Department/Logs.tvs/v1";
if (!String.IsNullOrEmpty(source))
{
String[] partsOfSource = source.Split('/');
if (partsOfSource != null)
{
if (partsOfSource.Length > 2)
{
component = partsOfSource[partsOfSource.Length - 2];
}
if (partsOfSource.Length > 1)
{
version = partsOfSource[partsOfSource.Length - 1];
}
}
}
Console.WriteLine(component);
Console.WriteLine(version);
Console.Read();
}

Why no regular expression? This one is fairly easy:
.*/(?<component>.*)/(?<version>.*)$
You can even label your groups so for your match all you need to do is:
component = myMatch.Groups["component"];
version = myMatch.Groups["version"];

The following should be faster, as it only scans as much of the string as it needs to to find two / and it doesn't bother splitting up the whole string:
string component = "";
string version = "";
string source = "Test/Company/Business/Department/Logs.tvs/v1";
int last = source.LastIndexOf('/');
if (last != -1)
{
int penultimate = source.LastIndexOf('/', last - 1);
version = source.Substring(last + 1);
component = source.Substring(penultimate + 1, last - penultimate - 1);
}
That said, as with all performance questions: profile! Try the two side-by-side with a big list of real-life inputs and see which is fastest.
(Also, this will leave empty strings rather than throw an exception if there is no slash in the input... but throw if source is null, lazy me.)

Your approach is the most suitable one given that your are looking for substrings at a particular index. A LINQ expression to do the same in this case will likely not improve the code or its readability.
For reference, there is some great information from Microsoft here on working with strings and LINQ. In particular see the article here which covers some examples with both LINQ and RegEx.
EDIT: +1 For Matt's named group within RegEx approach... that's the nicest solution I've seen.

Your code mostly looks fine. A couple of points to note:
String.Split() will never return null, so you don't need the null check on it.
If the source string has fewer than two / characters, how would you deal with that? (The Original Post was updated to address this)
Do you really want to just output empty strings if your source string is null or empty (or invalid)? If you have specific expectations about the nature of the input, you may want to consider failing fast when those expectations are not met.

You could try something like this but I doubt it would be much faster. You could do some meassurements with System.Diagnostics.StopWatch to see if you feel the need.
string source = "Test/Company/Business/Department/Logs.tvs/v1";
int index1 = source.LastIndexOf('/');
string last = source.Substring(index1 + 1);
string substring = source.Substring(0, index1);
int index2 = substring.LastIndexOf('/');
string secondLast = substring.Substring(index2 + 1);

I would try
string source = "Test/Company/Business/Department/Logs.tvs/v1";
var components = source.Split('/').Reverse().Take(2);
String last = string.Empty;
var enumerable = components as string[] ?? components.ToArray();
if (enumerable.Count() == 2)
last = enumerable.FirstOrDefault();
var secondLast = enumerable.LastOrDefault();
Hope this will help

you can retrieve the last two words using the process as below:
string source = "Test/Company/Business/Department/Logs.tvs/v1";
String[] partsOfSource = source.Split('/');
if(partsOfSourch.length>2)
for(int i=partsOfSourch.length-2;i<=partsOfSource.length-1;i++)
console.writeline(partsOfSource[i]);

get all characters to right of last dash

I have the following:
string test = "9586-202-10072"
How would I get all characters to the right of the final - so 10072. The number of characters is always different to the right of the last dash.
How can this be done?

You can get the position of the last - with str.LastIndexOf('-'). So the next step is obvious:
var result = str.Substring(str.LastIndexOf('-') + 1);
Correction:
As Brian states below, using this on a string with no dashes will result in the original string being returned.

You could use LINQ, and save yourself the explicit parsing:
string test = "9586-202-10072";
string lastFragment = test.Split('-').Last();
Console.WriteLine(lastFragment);

I can see this post was viewed over 46,000 times. I would bet many of the 46,000 viewers are asking this question simply because they just want the file name... and these answers can be a rabbit hole if you cannot make your substring verbatim using the at sign.
If you simply want to get the file name, then there is a simple answer which should be mentioned here. Even if it's not the precise answer to the question.
result = Path.GetFileName(fileName);
see https://msdn.microsoft.com/en-us/library/system.io.path.getfilename(v=vs.110).aspx

string tail = test.Substring(test.LastIndexOf('-') + 1);

YourString.Substring(YourString.LastIndexOf("-"));

With the latest C# 8 and later you can use Range Indexer as follows:-
string test = "9586-202-10072"
var foo = test?[(test.LastIndexOf('-') + 1)..];
// foo is => 10072

string atest = "9586-202-10072";
int indexOfHyphen = atest.LastIndexOf("-");
if (indexOfHyphen >= 0)
{
string contentAfterLastHyphen = atest.Substring(indexOfHyphen + 1);
Console.WriteLine(contentAfterLastHyphen );
}

See String.lastIndexOf method

I created a string extension for this, hope it helps.
public static string GetStringAfterChar(this string value, char substring)
{
if (!string.IsNullOrWhiteSpace(value))
{
var index = value.LastIndexOf(substring);
return index > 0 ? value.Substring(index + 1) : value;
}
return string.Empty;
}

test.Substring[(test.LastIndexOf('-') + 1)..]
C# 8 (late 2019) introduces range operator and simplifies it a bit further. The two dots here means from the index (inclusive) till the end of string.

test.Substring(test.LastIndexOf("-"))

and... in case you need the left part of a string:
private string AllTheLeftPart(string theString)
{
string rightPart = theString.Substring(theString.LastIndexOf('-') + 1);
string leftPart theString.Replace("-" + rightPart, String.Empty);
return leftPart ;
}

String functions

I want to search for a given string, within another string (Ex. find if "something" exists inside "something like this". How can I do the following? :
Know the position in which "something" is located (in the curr. ex. this is = 0.
Extract everything to the left or to the right, up to the char. found (see 1).
Extract a substring beggining where the sought string was found, all the way to X amount of chars (in Visual Basic 6/VBA I would use the Mid function).

string searched = "something like this";
1.
int pos = searched.IndexOf("something");
2.
string start = searched.Substring(0, pos);
string endstring = searched.Substring(pos);
3.
string mid = searched.Substring(pos, x);

Have you looked at the String.SubString() method? You can use the IndexOf() method to see if the substring exists first.

Take a look at the System.String member functions, in particular the IndexOf method.

Use int String.IndexOf(String).

I would do something like this:
string s = "I have something like this";
//question No. 1
int pos = s.IndexOf("something");
//quiestion No. 2
string[] separator = {"something"};
string[] leftAndRightEntries = s.Split(separator, StringSplitOptions.None);
//question No. 3
int x = pos + 10;
string substring = s.Substring(pos, x);

I would avoid using Split, as it's designed to give you multiple results. I would stick with the code in the first example, though the second block should actually read...
string start = searched.Substring(0, pos);
string endstring;
if(pos < searched.Length - 1)
endstring = searched.Substring(pos + "something".Length);
else
endstring = string.Empty
The key difference is accounting for the length of the string to find (hence the rather odd-looking "something".Length, as this example is designed for you to be able to plop in your own variable).