http://blog.darkhax.com/2009/05/12/pascal-case-to-human-readable-with-c-extension-methods

pascal_to_human.cs

public static string ToHumanFromPascal(this string s)
{
    if (2 > s.Length)
    {
        return s;
    }

    var sb = new StringBuilder();
    var ca = s.ToCharArray();
    sb.Append(ca[0]);
    for (int i = 1; i < ca.Length - 1; i++)
    {
        char c = ca[i];
        if (char.IsUpper(c) && (char.IsLower(ca[i + 1]) || char.IsLower(ca[i - 1])))
        {
            sb.Append(' ');
        }
        sb.Append(c);
    }
    sb.Append(ca[ca.Length - 1]);
    return sb.ToString();
}

Similar method using Regex from http://www.mehdi-khalili.com/bdd-simply-with-bddify
public static string CreateSentenceFromCamelName(string name)
{ return Regex.Replace(name, "[a-z][A-Z]", m => m.Value[0] + " " + char.ToLower(m.Value[1]));
}