Develop Reference

How to remove all but the first occurences of a character from a string?

I have a string of text and want to ensure that it contains at most one single occurrence of a specific character (,). Therefore I want to keep the first one, but simply remove all further occurrences of that character.
How could I do this the most elegant way using C#?

This works, but not the most elegant for sure :-)
string a = "12,34,56,789";
int pos = 1 + a.IndexOf(',');
return a.Substring(0, pos) + a.Substring(pos).Replace(",", string.Empty);

You could use a counter variable and a StringBuilder to create the new string efficiently:
var sb = new StringBuilder(text.Length);
int maxCount = 1;
int currentCount = 0;
char specialChar = ',';
foreach(char c in text)
if(c != specialChar || ++currentCount <= maxCount)
sb.Append(c);
text = sb.ToString();
This approach is not the shortest but it's efficient and you can specify the char-count to keep.
Here's a more "elegant" way using LINQ:
int commasFound = 0; int maxCommas = 1;
text = new string(text.Where(c => c != ',' || ++commasFound <= maxCommas).ToArray());
I don't like it because it requires to modify a variable from a query, so it's causing a side-effect.

Regular expressions are elegant, right?
Regex.Replace("Eats, shoots, and leaves.", #"(?<=,.*),", "");
This replaces every comma, as long as there is a comma before it, with nothing.
(Actually, it's probably not elegant - it may only be one line of code, but it may also be O(n^2)...)

If you don't deal with large strings and you reaaaaaaly like Linq oneliners:
public static string KeepFirstOccurence (this string #string, char #char)
{
var index = #string.IndexOf(#char);
return String.Concat(String.Concat(#string.TakeWhile(x => #string.IndexOf(x) < index + 1)), String.Concat(#string.SkipWhile(x=>#string.IndexOf(x) < index)).Replace(#char.ToString(), ""));
}

You could write a function like the following one that would split the string into two sections based on the location of what you were searching (via the String.Split() method) for and it would only remove matches from the second section (using String.Replace()) :
public static string RemoveAllButFirst(string s, string stuffToRemove)
{
// Check if the stuff to replace exists and if not, return the original string
var locationOfStuff = s.IndexOf(stuffToRemove);
if (locationOfStuff < 0)
{
return s;
}
// Calculate where to pull the first string from and then replace the rest of the string
var splitLocation = locationOfStuff + stuffToRemove.Length;
return s.Substring(0, splitLocation) + (s.Substring(splitLocation)).Replace(stuffToRemove,"");
}
You could simply call it by using :
var output = RemoveAllButFirst(input,",");
A prettier approach might actually involve building an extension method that handled this a bit more cleanly :
public static class StringExtensions
{
public static string RemoveAllButFirst(this string s, string stuffToRemove)
{
// Check if the stuff to replace exists and if not, return the
// original string
var locationOfStuff = s.IndexOf(stuffToRemove);
if (locationOfStuff < 0)
{
return s;
}
// Calculate where to pull the first string from and then replace the rest of the string
var splitLocation = locationOfStuff + stuffToRemove.Length;
return s.Substring(0, splitLocation) + (s.Substring(splitLocation)).Replace(stuffToRemove,"");
}
}
which would be called via :
var output = input.RemoveAllButFirst(",");
You can see a working example of it here.

static string KeepFirstOccurance(this string str, char c)
{
int charposition = str.IndexOf(c);
return str.Substring(0, charposition + 1) +
str.Substring(charposition, str.Length - charposition)
.Replace(c, ' ').Trim();
}

Pretty short with Linq; split string into chars, keep distinct set and join back to a string.
text = string.Join("", text.Select(c => c).Distinct());

How can I slice a string in c#?

string word = "hello";
So what I want to do is slice the string so that I can print, for example, elloh to the console window. In python it's so simple but I'm not sure if there's a specific method for slicing in c#.

A string can be indexed to get characters:
string word = "hello";
char h = word[0];
or strings have methods for "slicing":
int start = 0;
int length = 1;
string h = word.Substring(start, length);
Why not read the docs and find out for yourself?

There's no exact translation from the concept of a slicing, but a Substring is generally what you want.
It is unclear to me what your exact criteria is to slice it up, but this would do what you want:
void Main()
{
var input = "hello";
var output = input.Substring(1, input.Length - 1) + input.Substring(0, 1);
Console.WriteLine (output);
}

To "slice" a string, you use the Substring method:
string word = "hello";
string ordw = word.Substring(1) + word.Substring(0, 1);
However, a different answer would be to check out NSlice, a library built to handle python-like slicing of arrays.
Will it make it easier to do what you asked? No. Will it make it easier to "slice" different kinds of collections? Possibly.

you should use the substring function of string:
word.Substring(1);
http://msdn.microsoft.com/en-us/library/system.string.substring(v=vs.110).aspx

Maybe you want an extension method like this:
public static string Rotate(this string s, int numberOfChars)
{
if (string.IsNullOrEmpty(s))
return s;
numberOfChars %= s.Length;
if (numberOfChars == 0)
return s;
if (numberOfChars < 0)
numberOfChars += s.Length;
return s.Substring(numberOfChars) + s.Remove(numberOfChars);
}

How to concatenate a string with blankspaces?

I need to create a 10-character string. If the string has less than 10 characters i need to append blank spaces till complete the entire 10-character string. I do the following but I have no succes, the result string has only one blank space concateneted in the end:
public void MyMethod(string[] mystrings)
{
mystring[i].PadRight(10- mystrings[i].length)
// Here I need a 10 char string. For example:
// "1234567 "
}
Thank you.

You could use String.PadRight:
mystring = mystring.PadRight(10, ' ');
(You can omit the second parameter, as in your case, when you use spaces).
Note however, that if mystring is already longer than 10 characters, it will remain longer. It is not clear from your question, if you need a string with exactly 10 characters length. If so, then do something like:
mystring = mystring.PadRight(10).Substring(0, 10);

You can use string.Format with a custom format string:
mystring = string.Format("{0,-10}", mystring);

You need to use the string.PadRight method:
string result = mystring.PadRight(10);

try this
string str = "cc";
int charstoinsert = 10 - str.Length;
for (int i = 0; i < charstoinsert; i++)
{
str += " ";
}

Try with following function
#region GetPaddedString
private string GetPaddedString(string strValue, int intLength)
{
string strReturn = string.Empty;
string _strEmptySpace = " ";
int _vinLength = strValue.Length;
if (_vinLength < intLength)
{
strReturn = strValue + _strEmptySpace.PadRight((intLength - _vinLength));
}
else
{
strReturn = strValue;
}
return strReturn;
}
#endregion
GetPaddedString("test", 10)

This should do the trick:
str.PadRight(10, ' ').Substring(0, 10)

try this
string mystring= "sd";
while (mystring.Length <= 10)
{
mystring+= " ";
}

the easiest way to get number from string

i want to retrive some number from string, for example "valueID = 234232" or "valueID = 2" or "valueID=23" or "valueID= 2" or "valueID =234", so what is the easiest way to get this number assuming that after this number is space " " or end of line?

string input = "valueID = 234232";
var split = input.Split(new char[] {'='});
int value = int.Parse(split[1].Trim());

As long as your sure there will be a number in there
int.parse( Regex.match(String, #"\d+").value)

How about using a regex:
Match match = Regex.Match(input, #"\d+");
if (match.Success)
{
number = int.Parse(match.Value);
}

Here's some flexible code I use all the time for this sort of thing:
public const string FilterDigits = "0123456789";
public const string FilterLetters = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
/// <summary>
/// Strips away any characters not defined in validChars and returns the result.
/// </summary>
public static string FilterTo(string text, string validChars)
{
StringBuilder Result = new StringBuilder();
for (int i = 1; i <= text.Length; i++) {
char CurrentChar = Convert.ToChar(Strings.Mid(text, i, 1));
if (validChars.Contains(CurrentChar)) {
Result.Append(CurrentChar);
}
}
return Result.ToString;
}
Then you can just call:
int.parse(FilterTo("valueID=23", FilterDigits));
It could also be turned into a handy extension method, then you could do:
int.parse("valueID=23".FilterTo(FilterDigits));

Once you've parsed out your potential number (through regex, split, substr, etc), TryParse is a great improvement (since .NET 3.5 at least):
string myPotentialNumber = "1";
int myNumber;
bool isNumber = int.TryParse(myPotentialNumber, out myNumber);
if( isNumber )
{
//do something
}
else
{
//throw error
}
TryParse() is exception safe, which makes it a bit faster and cleaner for many types of conversions.

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