C# Determine if a char at index is between two characters in a string

Question

In C# how do I determine if a char at a certain index is between two characters in a string. I'm trying to do this to remove all spaces between quotes in a string. Example syntax: isBetween(string str, int index, char start, char end)

Thanks in advance

Edit: I also need it to work if start and end are the same character

Edit2: To clarify, I need it to work not only directly between, but it needs to work for other strings like isBetween("as((sup)hello)as", 5, '(', ')')

Answer 1

Based on the information given, and from what I understand about your question, you want an extension method for strings.

Something like this:

public class Program
{
    public static void Main()
    {
        var isBetween = "abc".IsBetween(1, 'a', 'c');
        Console.WriteLine(isBetween); //True
    }
}

public static class Extensions
{
    public static bool IsBetween(this String str, int index, char start, char end)
    {
        var left = str[index - 1];
        var right = str[index + 1];
        return left == start && right == end;
    }
}

The code above will check if the character at index 1 (which is b ), is between two characters ( a and c ). This returns true.

(Note that this does not account for index out of bound exceptions)

Answer 2

what I understood form your question. you are looking for something like this.

public class Program {
    public static void Main()
    {
      var isBetween = "abc".IsBetween('b', 'a', 'c', out int i);
      Console.WriteLine(isBetween); //True
      Console.WriteLine(i); //True
    }
  }

  public static class Extensions {
    public static bool IsBetween(this String str, char middle, char start, char end, out int index)
    {
      index = - 1;
      var left = str.IndexOf(start);
      var right = str.IndexOf(end);
      index = str.IndexOf(start) + 1 == str.IndexOf(end) -1 ? str.IndexOf(end) - 1: -1 ;
      return str[index] == middle ;

    }
  }

@ThePerplexedOne I did reuse your code.

Answer 3

Well, fro a public methid we should validate str , index and then check for chars at index - 1 , index + 1 :

public static bool IsBetween(this String str, int index, char start, char end) {
  return str != null &&                           // not null
         index >= 1 && index < str.Length - 1 &&  // valid index
         str[index - 1] == start &&               // char at index is between 
         str[index + 1] == stop;
} 

However, if you want to remove some characters (say, enquoted spaces), I suggest building a new string, eg

// "abc "  123   456 789" pq" -> "abc "123456789" pq"
public static string RemoveQuotedSpaces(String str) {
  if (string.IsNullOrEmpty(str))
    return str;

  StringBuilder sb = new StringBuilder(str.Length);

  bool inQuotation = false;

  foreach (char c in str) {
    if (c == '"')
      inQuotation != inQuotation;

    if (!inQuotation || c != ' ') 
      sb.Append(c);
  }

  return sb.ToString();  
}  

Answer 4

You can do this using RegularExpressions Demo

public class Program {
    public static void Main()
    {
      String xs = "aBc";
      var x= xs.ReplaceInBetween('a', 'c', 'B', 'b');      }
  }

  public static class Extensions {
    public static string ReplaceInBetween(this String str,  char start, char end, char middle, char replacewith)
    {
       Regex x = new Regex($"([{start}])({middle})([{end}])");
      str=  x.Replace(str, "$1" + replacewith + "$3");
      return str;
    }
  }

Answer 5

try this

public static bool IsBetween(String str, int index, char start, char end)
{
    var startIndex = str.Substring(0, index).LastIndexOf(start);
    var LastIndex = str.Substring(index).IndexOf(end);
    if (startIndex == -1 || LastIndex == -1)
        return false;

    LastIndex = LastIndex + index;
    return startIndex <= (index - 1) && LastIndex >= (index - 1);
}