string[] pic1 = productPic.Split('JPG');

------解决方案--------------------
应该是2L讲的原因

------解决方案--------------------
string[] pic1 = productPic.Split(new[] { "JPG" }, StringSplitOptions.None);

------解决方案--------------------
多字符分割有些许不同
char[] arrChr = “JPG”.ToCharArray();
string[] arr=productPic.Split(arrChr) ;

------解决方案--------------------
要看是传人参数是什么类型，char型就传char咯

------解决方案--------------------
C# code
用String.Split真的可以吗?
        static void Main()
        {
            String strTmp = "123.jpg456.jpg7j8p9g";

            char[] arrChr = "jpg".ToCharArray();
            string[] arr = strTmp.Split(arrChr);

            foreach (String s in arr)
            {
                Console.WriteLine(s);
            }

            Console.ReadKey();
        }

------解决方案--------------------
C# code
using System;
using System.Text.RegularExpressions;

namespace ConsoleApplication2
{
    class Program
    {
        static void Main()
        {
            String strTmp = "123.jpg456.jpg7j8p9g";

            char[] arrChr = "jpg".ToCharArray();
            string[] arr = Regex.Split(strTmp,"jpg");

            foreach (String s in arr)
            {
                Console.WriteLine(s);
            }

            Console.ReadKey();
        }
    }
}

------解决方案--------------------
试试这个
  Regex.Split(strTmp, "jpg").ToArray();