Replace first occurrence of pattern in a string

Question

Possible Duplicate    How do I replace the first instance of a string in  NET        Let s say I have the string   string s    Hello world      how can I replace the first o in the word Hello for let s say Foo   In other words I want to end up with    HellFoo world     I know how to replace all the o s but I want to replace just the first one

User · Answer

There are a number of ways that you could do this  but the fastest might be to use IndexOf to find the index position of the letter you want to replace and then substring out the text before and after what you want to replace

User · Answer

public string ReplaceFirst string text  string search  string replace      int pos   text IndexOf search     if  pos  lt  0          return text        return text Substring 0  pos    replace   text Substring pos   search Length       here is an Extension Method that could also work as well per VoidKing request  public static class StringExtensionMethods       public static string ReplaceFirst this string text  string search  string replace              int pos   text IndexOf search         if  pos  lt  0                  return text                return text Substring 0  pos    replace   text Substring pos   search Length

User · Answer

I think you can use the overload of Regex Replace to specify the maximum number of times to replace     var regex   new Regex Regex Escape  o     var newText   regex Replace  Hello World    Foo   1

[c#] Replace first occurrence of pattern in a string

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