Splits a string into blocks of a specified length, delimited by a specified string. License: MIT

SplitInParts.cs

/// <summary>
/// Splits a string into blocks of a specified length, delimited by a specified string.
/// </summary>
/// <param name="value">The string to split up.</param>
/// <param name="partLength">The number of characters between each delimiter.</param>
/// <param name="delimiter">The delimiter to be inserted.</param>
public static string SplitInParts(string value, int partLength, string delimiter)
{
  if (value == null) { throw new ArgumentNullException(nameof(value)); }
  if (partLength < 1) { throw new ArgumentException("Part length must be positive and greater than zero.", nameof(partLength)); }
  if (delimiter == null) { throw new ArgumentNullException(nameof(delimiter)); }

  if (delimiter.Length == 0 || value.Length <= partLength)
  {
    return value;
  }

  var builder = new StringBuilder(value[0].ToString(), value.Length + (delimiter.Length * ((value.Length - 1) / partLength)));
  for (int i = 1; i < value.Length; i++)
  {
    if (i % partLength == 0)
    {
      builder.Append(delimiter);
    }
    builder.Append(value[i]);
  }
  return builder.ToString();
}

// Usage:
SplitInParts("ABCDEFGHIJKLMNOPQRST", 5, "-");
// Returns: "ABCDE-FGHIJ-KLMNO-PQRST"