calling one program from another program

[arian]

hello.
I am new to using classes in C#.
I use visual studio 2005 and I have written 2 very simple program.
the frist one nameSpace=test1 and the nameSpace of the second one is test2.
I want to call the second one from the first program.I think I have to have both of them as 2 classes in the first program,am I right?
if yes
how can I have both of them as 2 classes in the first program(test1).
will you plz tell me what I should do?

thank you
Arian