StringExtensions.ToWords() converts "EnteringAirTemperature" to "Entering Air Temperature"; useful as a default convention for converting type names to human readable labels for display purposes.

StringExtensions.cs

    public static class StringExtensions 
    {
        /// <summary>
        /// Converts the string representation of <paramref name="src"/> to a human-readable format. 
        /// </summary>
        /// <example>"SomeEnumValue" becomes "Some Enum Value"</example>
        /// <example>"Some_Class_Name" becomes "Some Class Name"</example>
        /// <param name="src">the raw input to humanize</param>
        /// <param name="casingStyle">
        /// An optional <see cref="CasingStyle"/> lets you control how the string is rewritten.
        /// </param>
        /// <returns>A human-readible representation of <paramref name="src"/></returns>
        public static string ToWords(this object src, CasingStyle casingStyle = CasingStyle.AsIs)
        {
            return (src ?? String.Empty).ToString().ToWords(casingStyle);
        }

        public static string ToWords(this string src)
        {
            return ToWords(src, CasingStyle.AsIs);
        }

        static readonly Dictionary<CasingStyle, Func<char, char, bool, char>> CharTransformsByCasingStyle
            = new Dictionary<CasingStyle, Func<char, char, bool, char>> { 
				{CasingStyle.AsIs, (c, prev, isFirstChar) => c},
				{CasingStyle.TitleCase, (c, prev, isFirstChar) => c},
				{CasingStyle.AllLower, (c, prev, isFirstChar) => c.ToLower()},
				{CasingStyle.SentanceCase, (c, prev, isFirstChar) => isFirstChar ? c.ToUpper() : c.ToLower()}
		};

        public static string ToWords(this string src, CasingStyle casingStyle = CasingStyle.AsIs)
        {
            var sb = new StringBuilder();

            var transform = CharTransformsByCasingStyle[casingStyle];

            char last = char.MinValue;
            bool isFirst = true;
            foreach (char c in src)
            {
                if (c == '_')
                {
                    sb.Append(' ');
                    last = ' ';
                }
                else
                {
                    if (char.IsLower(last) && (char.IsUpper(c)))
                    {
                        sb.Append(' ');
                        last = ' ';
                    }
                    sb.Append(transform(c, last, isFirst));
                    last = c;
                }

                isFirst = false;
            }

            string value = sb.ToString().Trim();

            return casingStyle == CasingStyle.AllLower ? value.ToLowerInvariant() : value;
        }

        static char ToLower(this char c)
        {
            return c.ToString(CultureInfo.InstalledUICulture).ToLower().ToCharArray()[0];
        }

        static char ToUpper(this char c)
        {
            return c.ToString(CultureInfo.InvariantCulture).ToUpper().ToCharArray()[0];
        }

        public static string Underscore(this string src, bool forceLowerCase = true)
        {
            return src.ToWords(forceLowerCase ? CasingStyle.AllLower : CasingStyle.AsIs).Replace(' ', '_');
        }
    }

    /// <summary>
    /// Casing styles for the <see cref="StringExtensions.Humanize"/> methods
    /// </summary>
    public enum CasingStyle
    {
        AsIs,
        TitleCase,      // Each word capitalized
        SentanceCase,   // First word capitalized, following words lowercase
        AllLower,
    }