I have a value in a string with a semicolene and i would like to remove that semi colene and put a dot.

string a = 10:12;

string a = 10.12;

Use the Replace method.

just to add to ddanbe post (how to practicaly do it):

string a = "10:12";
a = a.Replace(":", ".");

Use the Replace method.

WOOOW tahts ccool thanks :)

You will slowely starting to experiance what C# offers. You will be amazed what you can do with it (almost everything it comes up into yout mind).
Just remember: nothing is impossible.
Even if you hardly can imagine something in your mind, it sure is possible to put this into working code.

Enjoy... :)