using System;
using System.Linq;
using System.Collections.Generic;
public class Test
{
public static void Main()
{
string str = "12.34.56.78";
Char replaceChar = '.';
int lastIndex = str.LastIndexOf(replaceChar);
if (lastIndex != -1)
{
IEnumerable<Char> chars = str
.Where((c, i) => c != replaceChar || i == lastIndex);
str = new string(chars.ToArray());
}
Console.Write(str);
}
}
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