Justin

private string FormatString(string transformString)
{
  if(string.IsNullOrEmpty(transformString))
     return transformString;
  return transformString.Substring(0, 1).ToUpper() + (transformString.Length > 1? transformString.Substring(1).ToLower():"");
}

方法二

string transformString= "value";

TextInfo textInfo = new CultureInfo("es-ES", false).TextInfo;

textInfo.ToTitleCase(transformString);