Split string

readme.md

The extension method SplitByCase given a string with upper/lowercased letters like KarenPayne will produce Karen Payne.

Alternates

string.Join(" ",Regex.Split(firstLastName, @"(?<!^)(?=[A-Z])"))

From stackoverflow

public static string InsertSpaceBeforeUpperCase(this string str)
{   
  var sb = new StringBuilder();

  char previousChar = char.MinValue; // Unicode '\0'

  foreach (char c in str)
  {
      if (char.IsUpper(c))
      {
          // If not the first character and previous character is not a space, insert a space before uppercase

          if (sb.Length != 0 && previousChar != ' ')
          {
              sb.Append(' ');
          }           
      }

      sb.Append(c);

      previousChar = c;
  }

  return sb.ToString();
}

Demo.cs

string firstLastName = "KarenPayne";
var separated = firstLastName.SplitByCase();

StringExtensions.cs

public static class StringExtensions
{
    public static string SplitByCase(this string input)
    {
        if (string.IsNullOrEmpty(input))
        {
            return input;
        }

        Span<char> result = stackalloc char[input.Length * 2];
        var resultIndex = 0;

        for (int index = 0; index < input.Length; index++)
        {
            char currentChar = input[index];

            if (index > 0 && char.IsUpper(currentChar))
            {
                result[resultIndex++] = ' ';
            }

            result[resultIndex++] = currentChar;
        }

        return result[..resultIndex].ToString();
    }

}