这是微软官方提供的解决方案，支持简体中午，繁体中文，韩语和日语。

需要安装依赖的 Visual Studio International Pack

下载地址：https://www.microsoft.com/zh-CN/download/details.aspx?id=15251

using System;
using System.Data;
using System.Configuration;
using Microsoft.International.Converters.PinYinConverter;

namespace Utility.Convert
{
    /// <summary>
    ///ChineseConvert 的摘要说明
    /// </summary>
    public class ChineseConvert
    {
        public ChineseConvert() { }

        /// <summary>
        /// 汉字转化为拼音
        /// </summary>
        /// <param name="str">汉字</param>
        /// <returns>全拼</returns>
        public static string GetPinyin(string str)
        {
            string r = string.Empty;
            foreach (char obj in str)
            {
                try
                {
                    ChineseChar chineseChar = new ChineseChar(obj);
                    string t = chineseChar.Pinyins[0].ToString();
                    r += t.Substring(0, t.Length - 1);
                }
                catch
                {
                    r += obj.ToString();
                }
            }
            return r;
        }

        /// <summary>
        /// 汉字转化为拼音首字母
        /// </summary>
        /// <param name="str">汉字</param>
        /// <returns>首字母</returns>
        public static string GetFirstPinyin(string str)
        {
            string r = string.Empty;
            foreach (char obj in str)
            {
                try
                {
                    ChineseChar chineseChar = new ChineseChar(obj);
                    string t = chineseChar.Pinyins[0].ToString();
                    r += t.Substring(0, 1);
                }
                catch
                {
                    r += obj.ToString();
                }
            }
            return r;
        }

    }
}