Reverse String Write Without Change Word Position In C#

I'm working on reversing a sentence. I'm able to do it. But I'm not sure, how to reverse the word without changing the special characters positions. I'm using regex but as soon as it finds the special characters it's stopping the reversal of the word.

Reverse string write without change word position in c#

static void Main(string[] args) {
    string orgstr = "my name is sagar";
    string revstr = "";
    foreach(var word in orgstr.Split(' ')) {
        string temp = "";
        foreach(var ch in word.ToCharArray()) {
            temp = ch + temp;
        }
        revstr = revstr + temp + " ";
    }
    Console.Write(revstr);
    Console.ReadKey();
}