Its a little ambiguous. do you want to know how to set file associations? or know how to catch the arguments passed to your app after its been associated?
I will assume the 2nd one, as the nature of the question looks to be of that.
you must modify your Main() function. If you are using microsoft visual studio on a Forms application this will be inside the "program.cs" file in the project solution. you must modify the Main method to accept a string array.
Public Static Void Main(string[] Args)
{
//you can use it here by using Args[0] to refference it or you can pass it to the first form like:
Application.Run(new Form1(Args));
}
of course if you send it to Form1 this way you must alter form1's constructor to accept it
string[] appArgs;
public Form1( string[] Args)
{
appArgs = Args;
}
happy coding!
Unsolved 
