Question

I’m having trouble with some syntax. I’m not really familiar with interfaces so please excuse my ignorance.

VS2010 is giving me an error at… application.Name = System.AppDomain.CurrentDomain.FriendlyName;

public static void AddApplication(string applicationName = null, string processImageFileName = null)
{
    INetFwAuthorizedApplications applications;
    INetFwAuthorizedApplication application;

    if(applicationName == null)
    {
        application.Name = System.AppDomain.CurrentDomain.FriendlyName;/*set the name of the application */
    }
    else
    {
        application.Name = applicationName;/*set the name of the application */
    }

    if (processImageFileName == null)
    {
        application.ProcessImageFileName = System.Reflection.Assembly.GetExecutingAssembly().Location; /* set this property to the location of the executable file of the application*/
    }
    else
    {
        application.ProcessImageFileName = processImageFileName; /* set this property to the location of the executable file of the application*/
    }

    application.Enabled =  true; //enable it

    /*now add this application to AuthorizedApplications collection */
    Type NetFwMgrType = Type.GetTypeFromProgID("HNetCfg.FwMgr", false); 
    INetFwMgr mgr = (INetFwMgr)Activator.CreateInstance(NetFwMgrType); 
    applications = (INetFwAuthorizedApplications)mgr.LocalPolicy.CurrentProfile.AuthorizedApplications;
    applications.Add(application);
}

I can make that error go away by setting application to null but that causes a run-time null reference error.

Edit:

Here’s where I’m adapting the code from. I hope it gives more context
http://blogs.msdn.com/b/securitytools/archive/2009/08/21/automating-windows-firewall-settings-with-c.aspx

Answer 1

You never initialize

application

before using it here:

application.Name = System.AppDomain.CurrentDomain.FriendlyName;

The variable application is defined as:

INetFwAuthorizedApplication application

You need to assign an instance of a class that implements the interface INetFwAuthorizedApplication.

Somewhere there must be one (or probably more) classes in your project that look something like this:

public class SomeClass : INetFwAuthorizedApplication
{
    // ...
}

public class AnotherClass : INetFwAuthorizedApplication
{
    // ...
}

You need to determine what class you should use (SomeClass, AnotherClass) then assign an appropriate object, e.g. like this:

INetFwAuthorizedApplication application = new SomeClass();