Ok,so your problem is "rounding" your variable to just one digit. There should be thousands of approaches,let me show you just the first it comes to my mind:
string[] version = pluginRegistrationEntity.PluginVersion.Split('.');
version[3] = (int.Parse(version[3]) + 1).ToString();
for (int i = 3; i > 0; i--)
{
if (version[i].Length > 1)
{
version[i] = "0";
version[i-1] = (int.Parse(version[i-1]) + 1).ToString(); ;
}
}
pluginRegistrationEntity.PluginVersion = version[0] + "." + version[1] + "." + version[2] + "." + version[3];
I'm sure there are better ways to do it,but i think this works.