/// <summary>
 /// Sets the font of the entire string.
 /// </summary>
 /// <param name="font">The font to use.</param>
 public void ApplyFont(NPOI.SS.UserModel.Font font)
 {
     ApplyFont(0, str.CharCount, font);
 }
 /// <summary>
 /// Applies a font to the specified Chars of a string.
 /// </summary>
 /// <param name="startIndex">The start index to apply the font to (inclusive).</param>
 /// <param name="endIndex"> The end index to apply to font to (exclusive).</param>
 /// <param name="font">The index of the font to use.</param>
 public void ApplyFont(int startIndex, int endIndex, NPOI.SS.UserModel.Font font)
 {
     ApplyFont(startIndex, endIndex, font.Index);
 }