See String Interpolation. Here's a quick example:
To convert a class or a type to a string, call the ToString() method. Or if you are writing your own class you can define your own ToString() method to control how your class is printed.
Converting from int to string and back
Parsing and converting other types
See this tutorial on the Parse and Convert techniques, as well as date parsing.
See the .NET reference on Basic String Operations for more information on string comparisons.