EPPlus/Utils/ConvertUtil.cs

using System;
using System.Globalization;
using System.IO;
using System.Text;
using System.Text.RegularExpressions;

namespace OfficeOpenXml.Utils;

internal static class ConvertUtil {
  internal static bool IsNumeric(object candidate) {
    if (candidate == null) {
      return false;
    }
    return (candidate.GetType().IsPrimitive
            || candidate is double
            || candidate is decimal
            || candidate is DateTime
            || candidate is TimeSpan
            || candidate is long);
  }

  internal static bool IsNumericString(object candidate) {
    if (candidate != null) {
      return Regex.IsMatch(candidate.ToString(), @"^[\d]+(\,[\d])?");
    }
    return false;
  }

  /// <summary>
  /// Convert an object value to a double
  /// </summary>
  /// <param name="v"></param>
  /// <param name="ignoreBool"></param>
  /// <returns></returns>
  internal static double GetValueDouble(object v, bool ignoreBool = false) {
    double d;
    try {
      if (ignoreBool && v is bool) {
        return 0;
      }
      if (IsNumeric(v)) {
        if (v is DateTime time) {
          d = time.ToOADate();
        } else if (v is TimeSpan span) {
          d = DateTime.FromOADate(0).Add(span).ToOADate();
        } else {
          d = Convert.ToDouble(v, CultureInfo.InvariantCulture);
        }
      } else {
        d = 0;
      }
    } catch {
      d = 0;
    }
    return d;
  }

  /// <summary>
  /// OOXML requires that "," , and &amp; be escaped, but ' and " should *not* be escaped, nor should
  /// any extended Unicode characters. This function only encodes the required characters.
  /// System.Security.SecurityElement.Escape() escapes ' and " as  &apos; and &quot;, so it cannot
  /// be used reliably. System.Web.HttpUtility.HtmlEncode overreaches as well and uses the numeric
  /// escape equivalent.
  /// </summary>
  /// <param name="s"></param>
  /// <returns></returns>
  internal static string ExcelEscapeString(string s) {
    return s.Replace("&", "&amp;").Replace("<", "&lt;").Replace(">", "&gt;");
  }

  /// <summary>
  /// Return true if preserve space attribute is set.
  /// </summary>
  /// <param name="sw"></param>
  /// <param name="t"></param>
  /// <returns></returns>
  internal static void ExcelEncodeString(StreamWriter sw, string t) {
    if (Regex.IsMatch(t, "(_x[0-9A-F]{4,4}_)")) {
      var match = Regex.Match(t, "(_x[0-9A-F]{4,4}_)");
      int indexAdd = 0;
      while (match.Success) {
        t = t.Insert(match.Index + indexAdd, "_x005F");
        indexAdd += 6;
        match = match.NextMatch();
      }
    }
    for (int i = 0; i < t.Length; i++) {
      if (t[i] <= 0x1f
          && t[i] != '\t'
          && t[i] != '\n'
          && t[i]
              != '\r') //Not Tab, CR or LF
      {
        sw.Write("_x00{0}_", (t[i] < 0xf ? "0" : "") + ((int)t[i]).ToString("X"));
      } else {
        sw.Write(t[i]);
      }
    }
  }

  /// <summary>
  /// Return true if preserve space attribute is set.
  /// </summary>
  /// <param name="sb"></param>
  /// <param name="t"></param>
  /// <returns></returns>
  internal static void ExcelEncodeString(StringBuilder sb, string t, bool encodeTabCrlf = false) {
    if (Regex.IsMatch(t, "(_x[0-9A-F]{4,4}_)")) {
      var match = Regex.Match(t, "(_x[0-9A-F]{4,4}_)");
      int indexAdd = 0;
      while (match.Success) {
        t = t.Insert(match.Index + indexAdd, "_x005F");
        indexAdd += 6;
        match = match.NextMatch();
      }
    }
    for (int i = 0; i < t.Length; i++) {
      if (t[i] <= 0x1f
          && ((t[i] != '\t' && t[i] != '\n' && t[i] != '\r' && encodeTabCrlf == false)
                  || encodeTabCrlf)) //Not Tab, CR or LF
      {
        sb.AppendFormat("_x00{0}_", (t[i] < 0xf ? "0" : "") + ((int)t[i]).ToString("X"));
      } else {
        sb.Append(t[i]);
      }
    }
  }

  /// <summary>
  /// Return true if preserve space attribute is set.
  /// </summary>
  /// <param name="sb"></param>
  /// <param name="t"></param>
  /// <returns></returns>
  internal static string ExcelEncodeString(string t) {
    StringBuilder sb = new StringBuilder();
    t = t.Replace("\r\n", "\n"); //For some reason can't table name have cr in them. Replace with nl
    ExcelEncodeString(sb, t, true);
    return sb.ToString();
  }

  internal static string ExcelDecodeString(string t) {
    var match = Regex.Match(t, "(_x005F|_x[0-9A-F]{4,4}_)");
    if (!match.Success) {
      return t;
    }

    var useNextValue = false;
    var ret = new StringBuilder();
    var prevIndex = 0;
    while (match.Success) {
      if (prevIndex < match.Index) {
        ret.Append(t.Substring(prevIndex, match.Index - prevIndex));
      }
      if (!useNextValue && match.Value == "_x005F") {
        useNextValue = true;
      } else {
        if (useNextValue) {
          ret.Append(match.Value);
          useNextValue = false;
        } else {
          ret.Append((char)int.Parse(match.Value.Substring(2, 4), NumberStyles.AllowHexSpecifier));
        }
      }
      prevIndex = match.Index + match.Length;
      match = match.NextMatch();
    }
    ret.Append(t.Substring(prevIndex, t.Length - prevIndex));
    return ret.ToString();
  }
}