C# Online Compiler | .NET Fiddle

using System;
using System.Text;
using System.Text.RegularExpressions;
					
public class Program
{
	public static void Main()
	{
		Console.WriteLine(MaskName("Petter Pan"));
		Console.WriteLine(MaskName("petter Pan"));
		Console.WriteLine(MaskName("張三"));
		Console.WriteLine(MaskName("王大明"));
		Console.WriteLine(MaskName("李小天"));
		Console.WriteLine(MaskName("蔡佩佩"));
		Console.WriteLine(MaskName("張簡明偉"));
		Console.WriteLine(MaskName("賽德克*巴萊"));
	}
	/// 姓名遮罩包含英文姓名
	/// 
	///
	/// 姓名
	/// 
	/// 王O名
	private static string MaskName(string val) {
		string maskstr, maskchar;
		maskchar = null;
		//符合英文的模式
		if (Regex.IsMatch(val, "[A-Za-z]"))
		{
			if (val.IndexOf("-") > 1)
			{
				maskstr = val.Split('-')[1];
				val = val.Replace(maskstr, "*");
			}
			if (val.IndexOf(" ") > 1)
			{
				maskstr = val.Split(' ')[1];
				val = val.Replace(maskstr, "*");
			}
		}
		else
		{ 
			//中文
			int strlen = val.Length;
			if(strlen==2){
				return val.Substring(0, 1)+"O";
			}
			if(strlen==3){
				return val.Substring(0, 1)+"O"+val.Substring(2, 1);
			}
			if(strlen>=4){
				return val.Substring(0, 2)+"O"+val.Substring(3, strlen-3);
			}			
		}            
		return val;
	}
}

 
using System;
using System.Text;
using System.Text.RegularExpressions;
                    
public class Program
{
    public static void Main()
    {
        Console.WriteLine(MaskName("Petter Pan"));
        Console.WriteLine(MaskName("petter Pan"));
        Console.WriteLine(MaskName("張三"));
        Console.WriteLine(MaskName("王大明"));
        Console.WriteLine(MaskName("李小天"));
        Console.WriteLine(MaskName("蔡佩佩"));
        Console.WriteLine(MaskName("張簡明偉"));
        Console.WriteLine(MaskName("賽德克*巴萊"));
    }
    /// 姓名遮罩包含英文姓名
    /// 
    ///
    /// 姓名
    /// 
    /// 王O名
    private static string MaskName(string val) {

Cached Result

Petter *
petter *
張O
王O明
李O天
蔡O佩
張簡O偉
賽德O*巴萊