Develop Reference

Trim a string in c# after special character

I want to trim a string after a special character..
Lets say the string is str="arjunmenon.uking". I want to get the characters after the . and ignore the rest. I.e the resultant string must be restr="uking".

How about:
string foo = str.EverythingAfter('.');
using:
public static string EverythingAfter(this string value, char c)
{
if(string.IsNullOrEmpty(value)) return value;
int idx = value.IndexOf(c);
return idx < 0 ? "" : value.Substring(idx + 1);
}

you can use like
string input = "arjunmenon.uking";
int index = input.LastIndexOf(".");
input = input.Substring(index+1, input.Split('.')[1].ToString().Length );

Use Split function
Try this
string[] restr = str.Split('.');
//restr[0] contains arjunmenon
//restr[1] contains uking

char special = '.';
var restr = str.Substring(str.IndexOf(special) + 1).Trim();

Try Regular Expression Language
using System.IO;
using System;
using System.Text.RegularExpressions;
class Program
{
static void Main()
{
string input = "arjunmenon.uking";
string pattern = #"[a-zA-Z0-9].*\.([a-zA-Z0-9].*)";
foreach (Match match in Regex.Matches(input, pattern))
{
Console.WriteLine(match.Value);
if (match.Groups.Count > 1)
for (int ctr = 1; ctr < match.Groups.Count; ctr++)
Console.WriteLine(" Group {0}: {1}", ctr, match.Groups[ctr].Value);
}
}
}
Result:
arjunmenon.uking
Group 1: uking

Personally, I won't do the split and go for the index[1] in the resulting array, if you already know that your correct stuff is in index[1] in the splitted string, then why don't you just declare a constant with the value you wanted to "extract"?
After you make a Split, just get the last item in the array.
string separator = ".";
string text = "my.string.is.evil";
string[] parts = text.Split(separator);
string restr = parts[parts.length - 1];
The variable restr will be = "evil"

string str = "arjunmenon.uking";
string[] splitStr = str.Split('.');
string restr = splitStr[1];

Not like the methods that uses indexes, this one will allow you not to use the empty string verifications, and the presence of your special caracter, and will not raise exceptions when having empty strings or string that doesn't contain the special caracter:
string str = "arjunmenon.uking";
string restr = str.Split('.').Last();
You may find all the info you need here : http://msdn.microsoft.com/fr-fr/library/b873y76a(v=vs.110).aspx
cheers

I think the simplest way will be this:
string restr, str = "arjunmenon.uking";
restr = str.Substring(str.LastIndexOf('.') + 1);

How can I search through a string in C# and replace areas bounded by a pattern?

We tried a few solutions now that try and use XML parsers. All fail because the strings are not always 100% valid XML. Here's our problem.
We have strings that look like this:
var a = "this is a testxxx of my data yxxx and of these xxx parts yxxx";
var b = "hello testxxx world yxxx ";
"this is a testxxx3yxxx and of these xxx1yxxx";
"hello testxxx1yxxx ";
The key here is that we want to do something to the data between xxx and yxxx. In the example above I would need a function that counts words and replaces the strings with a word count.
Is there a way we can process the string a and apply a function to change the data that's between the xxx and yxxx? Any function right now as we're just trying to get an idea of how to code this.

You can use Split method:
var parts = a.Split(new[] {"xxx", "yxxx"}, StringSplitOptions.None)
.Select((s, index) =>
{
string s1 = index%2 == 1 ? string.Format("{0}{2}{1}", "xxx", "yxxx", s + "1") : s;
return s1;
});
var result = string.Join("", parts);

If it always going to xxx and yxxx, you can use regex as suggested.
var stringBuilder = new StringBuilder();
Regex regex = new Regex("xxx(.*?)yxxx");
var splitGroups = Regex.Match(a);
foreach(var group in splitGroups)
{
var value = splitGroupsCopy[i];
// do something to value and then append it to string builder
stringBuilder.Append(string.Format("{0}{1}{2}", "xxx", value, "yxxx"));
}
I suppose this is as basic as it gets.

Using Regex.Replace will replace all the matches with your choice of text, something like this:
Regex rgx = new Regex("xxx.+yxxx");
string cleaned = rgx.Replace(a, "replacementtext");

This code will process each of the parts delimited by "xxx". It preserves the "xxx" separators. If you do not want to preserve the "xxx" separators, remove the two lines that say "result.Append(separator);".
Given:
"this is a testxxx of my data yxxx and there are many of these xxx parts yxxx"
It prints:
"this is a testxxx>> of my data y<<xxx and there are many of these xxx>> parts y<<xxx"
I'm assuming that's the kind of thing you want. Add your own processing to "processPart()".
using System;
using System.Text;
namespace ConsoleApplication1
{
internal class Program
{
private static void Main(string[] args)
{
string text = "this is a testxxx of my data yxxx and there are many of these xxx parts yxxx";
string separator = "xxx";
var result = new StringBuilder();
int index = 0;
while (true)
{
int start = text.IndexOf(separator, index);
if (start < 0)
{
result.Append(text.Substring(index));
break;
}
result.Append(text.Substring(index, start - index));
int end = text.IndexOf(separator, start + separator.Length);
if (end < 0)
{
throw new InvalidOperationException("Unbalanced separators.");
}
start += separator.Length;
result.Append(separator);
result.Append(processPart(text.Substring(start, end-start)));
result.Append(separator);
index = end + separator.Length;
}
Console.WriteLine(result);
}
private static string processPart(string part)
{
return ">>" + part + "<<";
}
}
}
[EDIT] Here's the code amended to work with two different separators:
using System;
using System.Text;
namespace ConsoleApplication1
{
internal class Program
{
private static void Main(string[] args)
{
string text = "this is a test<pre> of my data y</pre> and there are many of these <pre> parts y</pre>";
string separator1 = "<pre>";
string separator2 = "</pre>";
var result = new StringBuilder();
int index = 0;
while (true)
{
int start = text.IndexOf(separator1, index);
if (start < 0)
{
result.Append(text.Substring(index));
break;
}
result.Append(text.Substring(index, start - index));
int end = text.IndexOf(separator2, start + separator1.Length);
if (end < 0)
{
throw new InvalidOperationException("Unbalanced separators.");
}
start += separator1.Length;
result.Append(separator1);
result.Append(processPart(text.Substring(start, end-start)));
result.Append(separator2);
index = end + separator2.Length;
}
Console.WriteLine(result);
}
private static string processPart(string part)
{
return "|" + part + "|";
}
}
}

The indexOf() function will return to you the index of the first occurrence of a given substring.
(My indices might be a bit off, but) I would suggest doing something like this:
var searchme = "this is a testxxx of my data yxxx and there are many of these xxx parts yxxx";
var startindex= searchme.indexOf("xxx");
var endindex = searchme.indexOf("yxxx") + 3; //added 3 to find the index of the last 'x' instead of the index of the 'y' character
var stringpiece = searchme.substring(startindex, endindex - startindex);
and you can repeat that while startindex != -1
Like I said, the indices might be slightly off, you might have to add a +1 or -1 somewhere, but this will get you along nicely (I think).
Here is a little sample program that counts chars instead of words. But you should just need to change the processor function.
var a = "this is a testxxx of my data yxxx and there are many of these xxx parts yxxx";
a = ProcessString(a, CountChars);
string CountChars(string a)
{
return a.Length.ToString();
}
string ProcessString(string a, Func<string, string> processor)
{
int idx_start, idx_end = -4;
while ((idx_start = a.IndexOf("xxx", idx_end + 4)) >= 0)
{
idx_end = a.IndexOf("yxxx", idx_start + 3);
if (idx_end < 0)
break;
var string_in_between = a.Substring(idx_start + 3, idx_end - idx_start - 3);
var newString = processor(string_in_between);
a = a.Substring(0, idx_start + 3) + newString + a.Substring(idx_end, a.Length - idx_end);
idx_end -= string_in_between.Length - newString.Length;
}
return a;
}

I would use Regex Groups:
Here my solution to get the parts in the string:
private static IEnumerable<string> GetParts( string searchFor, string begin, string end ) {
string exp = string.Format("({0}(?<searchedPart>.+?){1})+", begin, end);
Regex regex = new Regex(exp);
MatchCollection matchCollection = regex.Matches(searchFor);
foreach (Match match in matchCollection) {
Group #group = match.Groups["searchedPart"];
yield return #group.ToString();
}
}
you can use it like to get the parts:
string a = "this is a testxxx of my data yxxx and there are many of these xxx parts yxxx";
IEnumerable<string> parts = GetParts(a, "xxx", "yxxx");
To replace the parts in the original String you can use the Regex Group to determine Length and StartPosition (#group.Index, #group.Length).

strip out digits or letters at the most right of a string

I have a file name: kjrjh20111103-BATCH2242_20111113-091337.txt
I only need 091337, not the txt or the - how can I achieve that. It does not have to be 6 numbers it could be more or less but will always be after "-" and the last ones before ."doc" or ."txt"

You can either do this with a regex, or with simple string operations. For the latter:
int lastDash = text.LastIndexOf('-');
string afterDash = text.Substring(lastDash + 1);
int dot = afterDash.IndexOf('.');
string data = dot == -1 ? afterDash : afterDash.Substring(0, dot);
Personally I find this easier to understand and verify than a regular expression, but your mileage may vary.

String fileName = kjrjh20111103-BATCH2242_20111113-091337.txt;
String[] splitString = fileName.Split ( new char[] { '-', '.' } );
String Number = splitString[2];

Regex: .*-(?<num>[0-9]*). should do the job. num capture group contains your string.

The Regex would be:
string fileName = "kjrjh20111103-BATCH2242_20111113-091337.txt";
string fileMatch = Regex.Match(fileName, "(?<=-)\d+", RegexOptions.IgnoreCase).Value;

String fileName = "kjrjh20111103-BATCH2242_20111113-091337.txt";
var startIndex = fileName.LastIndexOf('-') + 1;
var length = fileName.LastIndexOf('.') - startIndex;
var output = fileName.Substring(startIndex, length);

How to make a first letter capital in C#

How can the first letter in a text be set to capital?
Example:
it is a text. = It is a text.

public static string ToUpperFirstLetter(this string source)
{
if (string.IsNullOrEmpty(source))
return string.Empty;
// convert to char array of the string
char[] letters = source.ToCharArray();
// upper case the first char
letters[0] = char.ToUpper(letters[0]);
// return the array made of the new char array
return new string(letters);
}

It'll be something like this:
// precondition: before must not be an empty string
String after = before.Substring(0, 1).ToUpper() + before.Substring(1);

polygenelubricants' answer is fine for most cases, but you potentially need to think about cultural issues. Do you want this capitalized in a culture-invariant way, in the current culture, or a specific culture? It can make a big difference in Turkey, for example. So you may want to consider:
CultureInfo culture = ...;
text = char.ToUpper(text[0], culture) + text.Substring(1);
or if you prefer methods on String:
CultureInfo culture = ...;
text = text.Substring(0, 1).ToUpper(culture) + text.Substring(1);
where culture might be CultureInfo.InvariantCulture, or the current culture etc.
For more on this problem, see the Turkey Test.

If you are using C# then try this code:
Microsoft.VisualBasic.StrConv(sourceString, Microsoft.VisualBasic.vbProperCase)

I use this variant:
private string FirstLetterCapital(string str)
{
return Char.ToUpper(str[0]) + str.Remove(0, 1);
}

If you are sure that str variable is valid (never an empty-string or null), try:
str = Char.ToUpper(str[0]) + str[1..];
Unlike the other solutions that use Substring, this one does not do additional string allocations. This example basically concatenates char with ReadOnlySpan<char>.

I realize this is an old post, but I recently had this problem and solved it with the following method.
private string capSentences(string str)
{
string s = "";
if (str[str.Length - 1] == '.')
str = str.Remove(str.Length - 1, 1);
char[] delim = { '.' };
string[] tokens = str.Split(delim);
for (int i = 0; i < tokens.Length; i++)
{
tokens[i] = tokens[i].Trim();
tokens[i] = char.ToUpper(tokens[i][0]) + tokens[i].Substring(1);
s += tokens[i] + ". ";
}
return s;
}
In the sample below clicking on the button executes this simple code outBox.Text = capSentences(inBox.Text.Trim()); which pulls the text from the upper box and puts it in the lower box after the above method runs on it.

Take the first letter out of the word and then extract it to the other string.
strFirstLetter = strWord.Substring(0, 1).ToUpper();
strFullWord = strFirstLetter + strWord.Substring(1);

text = new String(
new [] { char.ToUpper(text.First()) }
.Concat(text.Skip(1))
.ToArray()
);

this functions makes capital the first letter of all words in a string
public static string FormatSentence(string source)
{
var words = source.Split(' ').Select(t => t.ToCharArray()).ToList();
words.ForEach(t =>
{
for (int i = 0; i < t.Length; i++)
{
t[i] = i.Equals(0) ? char.ToUpper(t[i]) : char.ToLower(t[i]);
}
});
return string.Join(" ", words.Select(t => new string(t)));;
}

string str = "it is a text";
// first use the .Trim() method to get rid of all the unnecessary space at the begining and the end for exemple (" This string ".Trim() is gonna output "This string").
str = str.Trim();
char theFirstLetter = str[0]; // this line is to take the first letter of the string at index 0.
theFirstLetter.ToUpper(); // .ToTupper() methode to uppercase the firstletter.
str = theFirstLetter + str.substring(1); // we add the first letter that we uppercased and add the rest of the string by using the str.substring(1) (str.substring(1) to skip the first letter at index 0 and only print the letters from the index 1 to the last index.)
Console.WriteLine(str); // now it should output "It is a text"

static String UppercaseWords(String BadName)
{
String FullName = "";
if (BadName != null)
{
String[] FullBadName = BadName.Split(' ');
foreach (string Name in FullBadName)
{
String SmallName = "";
if (Name.Length > 1)
{
SmallName = char.ToUpper(Name[0]) + Name.Substring(1).ToLower();
}
else
{
SmallName = Name.ToUpper();
}
FullName = FullName + " " + SmallName;
}
}
FullName = FullName.Trim();
FullName = FullName.TrimEnd();
FullName = FullName.TrimStart();
return FullName;
}

string Input = " it is my text";
Input = Input.TrimStart();
//Create a char array
char[] Letters = Input.ToCharArray();
//Make first letter a capital one
string First = char.ToUpper(Letters[0]).ToString();
//Concatenate
string Output = string.Concat(First,Input.Substring(1));

Try this code snippet:
char nm[] = "this is a test";
if(char.IsLower(nm[0])) nm[0] = char.ToUpper(nm[0]);
//print result: This is a test

How do I replace the *first instance* of a string in .NET?

I want to replace the first occurrence in a given string.
How can I accomplish this in .NET?

string ReplaceFirst(string text, string search, string replace)
{
int pos = text.IndexOf(search);
if (pos < 0)
{
return text;
}
return text.Substring(0, pos) + replace + text.Substring(pos + search.Length);
}
Example:
string str = "The brown brown fox jumps over the lazy dog";
str = ReplaceFirst(str, "brown", "quick");
EDIT: As #itsmatt mentioned, there's also Regex.Replace(String, String, Int32), which can do the same, but is probably more expensive at runtime, since it's utilizing a full featured parser where my method does one find and three string concatenations.
EDIT2: If this is a common task, you might want to make the method an extension method:
public static class StringExtension
{
public static string ReplaceFirst(this string text, string search, string replace)
{
// ...same as above...
}
}
Using the above example it's now possible to write:
str = str.ReplaceFirst("brown", "quick");

As itsmatt said Regex.Replace is a good choice for this however to make his answer more complete I will fill it in with a code sample:
using System.Text.RegularExpressions;
...
Regex regex = new Regex("foo");
string result = regex.Replace("foo1 foo2 foo3 foo4", "bar", 1);
// result = "bar1 foo2 foo3 foo4"
The third parameter, set to 1 in this case, is the number of occurrences of the regex pattern that you want to replace in the input string from the beginning of the string.
I was hoping this could be done with a static Regex.Replace overload but unfortunately it appears you need a Regex instance to accomplish it.

Take a look at Regex.Replace.

using System.Text.RegularExpressions;
RegEx MyRegEx = new RegEx("F");
string result = MyRegex.Replace(InputString, "R", 1);
will find first F in InputString and replace it with R.

Taking the "first only" into account, perhaps:
int index = input.IndexOf("AA");
if (index >= 0) output = input.Substring(0, index) + "XQ" +
input.Substring(index + 2);
?
Or more generally:
public static string ReplaceFirstInstance(this string source,
string find, string replace)
{
int index = source.IndexOf(find);
return index < 0 ? source : source.Substring(0, index) + replace +
source.Substring(index + find.Length);
}
Then:
string output = input.ReplaceFirstInstance("AA", "XQ");

C# extension method that will do this:
public static class StringExt
{
public static string ReplaceFirstOccurrence(this string s, string oldValue, string newValue)
{
int i = s.IndexOf(oldValue);
return s.Remove(i, oldValue.Length).Insert(i, newValue);
}
}

In C# syntax:
int loc = original.IndexOf(oldValue);
if( loc < 0 ) {
return original;
}
return original.Remove(loc, oldValue.Length).Insert(loc, newValue);

Assumes that AA only needs to be replaced if it is at the very start of the string:
var newString;
if(myString.StartsWith("AA"))
{
newString ="XQ" + myString.Substring(2);
}
If you need to replace the first occurrence of AA, whether the string starts with it or not, go with the solution from Marc.

And because there is also VB.NET to consider, I would like to offer up:
Private Function ReplaceFirst(ByVal text As String, ByVal search As String, ByVal replace As String) As String
Dim pos As Integer = text.IndexOf(search)
If pos >= 0 Then
Return text.Substring(0, pos) + replace + text.Substring(pos + search.Length)
End If
Return text
End Function

One of the overloads of Regex.Replace takes an int for "The maximum number of times the replacement can occur". Obviously, using Regex.Replace for plain text replacement may seem like overkill, but it's certainly concise:
string output = (new Regex("AA")).Replace(input, "XQ", 1);

For anyone that doesn't mind a reference to Microsoft.VisualBasic, there is the Replace Method:
string result = Microsoft.VisualBasic.Strings.Replace("111", "1", "0", 2, 1); // "101"

This example abstracts away the substrings (but is slower), but is probably much fast than a RegEx:
var parts = contents.ToString().Split(new string[] { "needle" }, 2, StringSplitOptions.None);
return parts[0] + "replacement" + parts[1];

Updated extension method utilizing Span to minimize new string creation
public static string ReplaceFirstOccurrence(this string source, string search, string replace) {
int index = source.IndexOf(search);
if (index < 0) return source;
var sourceSpan = source.AsSpan();
return string.Concat(sourceSpan.Slice(0, index), replace, sourceSpan.Slice(index + search.Length));
}

With ranges and C# 10 we can do:
public static string ReplaceFirst(this string text, string search, string replace)
{
int pos = text.IndexOf(search, StringComparison.Ordinal);
return pos < 0 ? text : string.Concat(text[..pos], replace, text.AsSpan(pos + search.Length));
}

string abc = "AAAAX1";
if(abc.IndexOf("AA") == 0)
{
abc.Remove(0, 2);
abc = "XQ" + abc;
}