C# Extension Method for String Data Type

Question

My web application deals with strings that need to be converted to numbers a lot - users often put commas, units (like cm, m, g, kg) and currency symbols in these fields so

Answer 1

Just answering the how do I create extension method for string class:

public static class MyStringExtensions {
public static ToDecimal(this string input) {
   // ...
}
}

(and you need to have an using statement for the namespace it is located in order to use it)