We Keep Coding

How to trim string started from substring

How to remove in elegance way second part of string starting from particular substring?
Ex.
We have string:
var someString = "ThisIsSomeString_v1_26102017";
as a result we want: ThisIsSomeString
I did that:
var someString = "ThisIsSomeString_v1_26102017";
var tokens = someString.SplitByLast("_v");
var result = tokens[0];
There is any clever way to do that? Some Trim or something?
I mean as a result I want to have first part of string. In this case separator is a "_v" substring. I want to drop everything after "_v" included this "_v".

Use string.Substring:
var result = someString.Substring(0, Math.Max(someString.IndexOf("_v"), 0));

Not any better than the Substring implementation, the Split might look like this:
var result = someString.Split(new[]{"_v"}, StringSplitOptions.None).First();

Do like this -
var result = str.Substring(0, str.LastIndexOf("_v"));
It will remove all the text after _v (including _v).

What's wrong with:
var result = input?.Split(new[] { "_v" }, StringSplitOptions.None)[0];

C# substring after specific sign

how can I get a value of the string after last'/'
string path=http://localhost:26952/Images/Users/John.jpg
I would like to have as a result something like :
John.jpg

I think using Path.GetFileName method is a better way instead of string manipulation.
string path = "http://localhost:26952/Images/Users/John.jpg";
var result = Path.GetFileName(path);
Console.WriteLine(result); // John.jpg

Split by '/' and get the last part:
var url = "http://localhost:26952/Images/Users/John.jpg";
var imageName = url.Split('/').Last();

The fastest way to trim string in C#

I need to trim paths in million strings like this:
C:\workspace\my_projects\my_app\src\my_component\my_file.cpp
to
src\my_component\my_file.cpp
I.e. remove absolute part of the path, what is the fastest way to do that?
My try using regex:
Regex.Replace(path, #"(.*?)\src", ""),

I wouldn't go with regex for this, use the plain old method.
If the path prefix is always the same:
const string partToRemove = #"C:\workspace\my_projects\my_app\";
if (path.StartsWith(partToRemove, StringComparison.OrdinalIgnoreCase))
path = path.Substring(partToRemove.Length);
If the prefix is variable, you can get the last index of \src\:
var startIndex = path.LastIndexOf(#"\src\", StringComparison.OrdinalIgnoreCase);
if (startIndex >= 0)
path = path.Substring(startIndex + 1);

define the regex with a new and reuse it
there is a (significant) cost to creating the regex
string input = "This is text with far too much " +
"whitespace.";
string pattern = "\\s+";
string replacement = " ";
Regex rgx = new Regex(pattern);
string result = rgx.Replace(input, replacement);

I'm not sure if you need speed here, but if you always get the full path, you could do a simple .Substring()
var path = #"C:\workspace\my_projects\my_app\src\my_component\my_file.cpp";
Console.WriteLine(path.Substring(32));
However, I think you should sanitize your input first; in this case, the Uri class could do the parsing step:
var root = #"C:\workspace\my_projects\my_app\";
var path = #"C:\workspace\my_projects\my_app\src\my_component\my_file.cpp";
var relative = new Uri(root).MakeRelativeUri(new Uri(path));
Console.WriteLine(relative.OriginalString.Replace("/", "\\"));
Notice here the Uri will change the \ with a /: that's the .Replace reason.

Cant think any faster than this
path.Substring(33);
What is before src is constant. and it starts from index 33.
C:\workspace\my_projects\my_app\src\my_component\my_file.cpp
^
How ever if its not always constant. you can find it once. and do the rest inside loop.
int startInd = path.IndexOf(#"\src\") + 1;
// Do this inside loop. 1 million times
path.Substring(startInd);

If your files will all end in "src/filename.ext" you could use the Path class in the .NET framework for it and get around all caveats you could have with pathes and filenames:
result = "src\" + Path.GetFileName(path);
So you should first double-check that the conversion is the thing that takes to long.

Get the last path of URL

I'm using the following code which is working just fine for most of the services but some time in the URL last I got User;v=2;mp and I need to get just User,how should I handle it?
I need some general solution since I guess in some other URL I can get different spacial charters
if the URL
https://ldmrrt.ct/odata/GBSRM/User;v=2;mp
string serviceName = _uri.Segments.LastOrDefault();
if the URL is https://ldmrrt.ct/odata/GBSRM/User its working fine...

Just replace:
string serviceName = _uri.Segments.LastOrDefault();
With:
string serviceName = _uri.Segments.LastOrDefault().Split(new[]{';'}).First();
If you need something more flexible, where you can specify what characters to include or skip, you could do something like this (slightly messy, you should probably extract parts of this as separate variables, etc):
// Note the _ and - characters in this example:
Uri _uri = new Uri("https://ldmrrt.ct/odata/GBSRM/User_ex1-ex2;v=2;mp");
// This will return a string: "User_ex1-ex2"
string serviceName =
new string(_uri.Segments
.LastOrDefault()
.TakeWhile(c => Char.IsLetterOrDigit(c)
|| (new char[]{'_', '-'}).Contains(c))
.ToArray());
Update, in response to what I understand to be a question below :) :
You could just use a String.Replace() for that, or you could use filtering by doing something like this:
// Will return: "Userexex2v=2mp"
string serviceName =
new string(_uri.Segments
.LastOrDefault()
.Where(c =>
!Char.IsPunctuation(c) // Ignore punctuation
// ..and ignore any "_" or "-":
&& !(new char[]{'_', '-'}).Contains(c))
.ToArray());
If you use this in production, mind you, be sure to clean it up a little, e.g. by splitting into several variables, and defining your char[]-array prior to usage.

In your case you can try to split a "User;v=2;mp" string.
string [] split = words.Split(new Char [] { ';' });
Returns a string array that contains the substrings in this instance that are delimited by elements of a specified Unicode character array.
split.First();
or:
split[0];

extract query string from a URL string

I am reading from history, and I want that when i come across a google query, I can extract the query string. I am not using request or httputility since i am simply parsing a string. however, when i come across URLs like this, my program fails to parse it properly:
http://www.google.com.mt/search?client=firefox-a&rls=org.mozilla%3Aen-US%3Aofficial&channel=s&hl=mt&source=hp&biw=986&bih=663&q=hotmail&meta=&btnG=Fittex+bil-Google
what i was trying to do is get the index of q= and the index of & and take the words in between but in this case the index of & will be smaller than q= and it will give me errors.
any suggestions?
thanks for your answers, all seem good :) p.s. i couldn't use httputility, not I don't want to. when i add a reference to system.web, httputility isn't included! it's only included in an asp.net application. Thanks again

It's not clear why you don't want to use HttpUtility. You could always add a reference to System.Web and use it:
var parsedQuery = HttpUtility.ParseQueryString(input);
Console.WriteLine(parsedQuery["q"]);
If that's not an option then perhaps this approach will help:
var query = input.Split('&')
.Single(s => s.StartsWith("q="))
.Substring(2);
Console.WriteLine(query);
It splits on & and looks for the single split result that begins with "q=" and takes the substring at position 2 to return everything after the = sign. The assumption is that there will be a single match, which seems reasonable for this case, otherwise an exception will be thrown. If that's not the case then replace Single with Where, loop over the results and perform the same substring operation in the loop.
EDIT: to cover the scenario mentioned in the comments this updated version can be used:
int index = input.IndexOf('?');
var query = input.Substring(index + 1)
.Split('&')
.SingleOrDefault(s => s.StartsWith("q="));
if (query != null)
Console.WriteLine(query.Substring(2));

If you don't want to use System.Web.HttpUtility (thus be able to use the client profile), you can still use Mono HttpUtility.cs which is only an independent .cs file that you can embed in your application. Then you can simply use the ParseQueryString method inside the class to parse the query string properly.

here is the solution -
string GetQueryString(string url, string key)
{
string query_string = string.Empty;
var uri = new Uri(url);
var newQueryString = HttpUtility.ParseQueryString(uri.Query);
query_string = newQueryString[key].ToString();
return query_string;
}

Why don't you create a code which returns the string from the q= onwards till the next &?
For example:
string s = historyString.Substring(url.IndexOf("q="));
int newIndex = s.IndexOf("&");
string newString = s.Substring(0, newIndex);
Cheers

Use the tools available:
String UrlStr = "http://www.google.com.mt/search?client=firefox-a&rls=org.mozilla%3Aen-US%3Aofficial&channel=s&hl=mt&source=hp&biw=986&bih=663&q=hotmail&meta=&btnG=Fittex+bil-Google";
NameValueCollection Items = HttpUtility.ParseQueryString(UrlStr);
String QValue = Items["q"];

If you really need to do the parsing yourself, and are only interested in the value for 'q' then the following would work:
string url = #"http://www.google.com.mt/search?" +
"client=firefoxa&rls=org.mozilla%3Aen-" +
"US%3Aofficial&channel=s&hl=mt&source=hp&" +
"biw=986&bih=663&q=hotmail&meta=&btnG=Fittex+bil-Google";
int question = url.IndexOf("?");
if(question>-1)
{
int qindex = url.IndexOf("q=", question);
if (qindex > -1)
{
int ampersand = url.IndexOf('&', qindex);
string token = null;
if (ampersand > -1)
token = url.Substring(qindex+2, ampersand - qindex - 2);
else
token = url.Substring(qindex+2);
Console.WriteLine(token);
}
}
But do try to look at using a proper URL parser, it will save you a lot of hassle in the future.
(amended this question to include a check for the '?' token, and support 'q' values at the end of the query string (without the '&' at the end) )

And that's why you should use Uri and HttpUtility.ParseQueryString.

HttpUtility is fine for the .Net Framework. However that class is not available for WinRT apps. If you want to get the parameters from a url in a Windows Store App you need to use WwwFromUrlDecoder. You create an object from this class with the query string you want to get the parameters from, the object has an enumerator and supports also lambda expressions.
Here's an example
var stringUrl = "http://localhost/?name=Jonathan&lastName=Morales";
var decoder = new WwwFormUrlDecoder(stringUrl);
//Using GetFirstByName method
string nameValue = decoder.GetFirstByName("name");
//nameValue has "Jonathan"
//Using Lambda Expressions
var parameter = decoder.FirstOrDefault(p => p.Name.Contains("last")); //IWwwFormUrlDecoderEntry variable type
string parameterName = parameter.Name; //lastName
string parameterValue = parameter.Value; //Morales
You can also see http://www.dzhang.com/blog/2012/08/21/parsing-uri-query-strings-in-windows-8-metro-style-apps