Monitoring multiple forms from class library

Question

I am trying to write a class NvApplicationContext which inherits from ApplicationContext, in a class library, and which I will use to monitor activity in multiple forms.

public class NvApplicationContext : ApplicationContext {
    // ...

    public NvApplicationContext(Form f) {

    }

    // ...
}

However, I can only seem to pass in one form (an instance of Form1) from my end projects:

NvApplicationContext nvca = new NvApplicationContext(new Form1()); 
Application.Run(nvca);

Are the rest of the forms supposed to be recognized automatically? Or, how can multiple forms be monitored by NvApplicationContext?

Can you be more specific about what you're trying to do? What do you mean by "monitor multiple forms"? — , Jul 25 '18 at 03:35
Your `ApplicationContext`-derived class needs to hold references to the new `Form`s you are creating; it won't automatically close all forms when it is finished. See [here](https://stackoverflow.com/a/13406508/111794) and [here](https://stackoverflow.com/a/13407161/111794). — Zev Spitz, Jul 25 '18 at 03:52
Sorry, my bad. I have an application containing two forms and I want to monitor those two forms using a class library. The Application opens form1 on start and another form on button click. I am using ApplicationContext in this way :- NvApplicationContext nvca = new NvApplicationContext(new Form1()); Application.Run(nvca); and hence I am getting only reference of form1. How do I get the reference of form2 in class library. NVApplicationContext is extending ApplicationContext and this class is in class library. — AKS, Jul 25 '18 at 04:40
The `ApplicationContext` pattern has already been covered by the (good, btw) example linked by @Zev Spitz. Another way is using [Automation](https://learn.microsoft.com/en-us/dotnet/api/system.windows.automation.automation?f1url=https%3A%2F%2Fmsdn.microsoft.com%2Fquery%2Fdev15.query%3FappId%3DDev15IDEF1%26l%3DEN-US%26k%3Dk(System.Windows.Automation.Automation);k(TargetFrameworkMoniker-.NETFramework&view=netframework-4.7.2)). But it depends on what you mean by *monitoring*. Try to explain it (by editing your question) in a more consistent way. — Jimi, Jul 25 '18 at 05:17
@Jimi Would you suggest any improvements on either of the two linked answers? — Zev Spitz, Jul 25 '18 at 05:24
@Zev Spitz I think that [this one](https://stackoverflow.com/a/13407161/7444103) is quite well implemented. But I can't express a qualified opinion without testing it. It's quite interesting, though (and the reason why I commented here), because just a few hours ago I answered a question (somewhat similar) about [*managing* an existing app Forms](https://stackoverflow.com/questions/51491566/add-an-event-to-all-forms-in-a-project?answertab=active#tab-top) (without editing the existing code). `ApplicationContext` was one of the methods that came to mind. Your solution is interesting. — Jimi, Jul 25 '18 at 05:41
Again, your `NvApplicationContext` has to be told about new forms that you create. If you look at [this answer](https://stackoverflow.com/questions/9462592/best-practices-for-multi-form-applications-to-show-and-hide-forms/13407161#13407161), there are two additional members described: `CreateForm` creates new form instances through the context, which then registers the newly created forms; and `RegisterForm` which registers forms not created via the context. — Zev Spitz, Jul 25 '18 at 05:54
@Zev I might get help with the first solution you provided. Its just I am struggling how do I pass context having reference to all the forms. — AKS, Jul 25 '18 at 05:55
You could define `NvApplicationContext` as taking a variable number of arguments: `public NvApplicationContext(params Form[] forms) [ ... }` which would allow you to pass multiple forms into the constructor. Alternatively, instead of passing forms into the constructor, you could implement a `RegisterForm` method in `NvApplicationContext` (see [here](https://stackoverflow.com/a/13407161/111794)) and pass the newly created Form instances to the `RegisterForm` method. — Zev Spitz, Jul 25 '18 at 06:01
Thanks @Zev. I am getting forms in my class library but none of the event handler is working. I mean on identification of forms, I am applying click handler on it which is not working when I am clicking on the form. Any comments on that? — AKS, Jul 25 '18 at 14:33
@user10122634 I've expanded my comments into a full answer. If after that you are still having trouble, I suggest you ask a new question. — Zev Spitz, Jul 25 '18 at 17:03
Also, I've rewritten your question; please make sure it reflects your original intention. — Zev Spitz, Jul 25 '18 at 17:39

Zev Spitz · Accepted Answer · 2018-07-27T10:06:56.610

Your NvApplicationContext needs to be told about any form instance that you want the context class to manage; it does not happen automatically.

I can think of multiple ways to structure this:

Allow your constructor to take multiple Form instances, using params
Add a RegisterForm method to NvApplicationContext and call whenever you create a form that needs to be monitored
Add a CreateForm method to NvApplicationContext and use it to create a form that needs to be monitored
In the class library, create a base form class that registers itself on creation, and have your Form1 and Form2 inherit from that base class

Allow constructor to take multiple `Form`s

In the class library:

public class NvApplicationContext : ApplicationContext {
    public NvApplicationContext(params Form[] forms) {
        // register event handler on each form here
    }
}

and used like this in the end projects:

var nvca = new NvApplicationContext(new Form1(), new Form2(), new Form3()); 
Application.Run(nvca);

Using a `RegisterForm` method

Define a static instance of NvApplicationContext:

public class NvApplicationContext : ApplicationContext {
    public static readonly NvApplicationContext Current = new NvApplicationContext();

    public void RegisterForm(Form frm) {
        // register event handler on form here
    }
}

and call RegisterForm once you've created the form. This could be before the call to Application.Run:

NvApplicationContext.Current.RegisterForm(new Form1());
NvApplicationContext.Current.RegisterForm(new Form2());
NvApplicationContext.Current.RegisterForm(new Form3());
Application.Run(NvApplicationContext.Current);

or anywhere in the application, because NvApplicationContext.Current is a static field and globally available.

Using a `CreateForm` method

Another option is to create any form that needs to be managed, via NvApplicationContext, and it will take care of registering the form. This assumes a static instance of the context, as in the previous section:

public class NvApplicationContext : ApplicationContext {
    public static readonly NvApplicationContext Current = new NvApplicationContext();

    public T CreateForm<T>() where T : Form, new() {
        var ret = new T();

        // register event handlers here

        return ret;
    }
}

and then call before Application.Run

NvApplicationContext.Current.CreateForm<Form1>();
NvApplicationContext.Current.CreateForm<Form2>();
NvApplicationContext.Current.CreateForm<Form3>();
Application.Run(NvApplicationContext.Current);

Using a base form

You could write a base form class like this (either in your class library, or in the end project), calling RegisterForm with a static instance from before:

public class BaseForm : Form {
    public BaseForm() {
        NvApplicationContext.Current.RegisterForm(this);
    }
}

and create forms that inherit from the base class either with the UI:

Visual Studio Add Item dialog box

Visual Studio Inheritance Picker dialog box

Or, you could do this from the code-behind of the form. Modify the base class from Form to BaseForm:

public partial class Form1 : BaseForm {
    public Form1() {
        InitializeComponent();
    }
}

Once you've set up the inheritance, whenever you create a new instance of the form it will automatically be registered with NvApplicationContext.Current.

new Form1();
new Form2();
new Form3();
Application.Run(NvApplicationContext.Current);

Thanks for the efforts. I did this way(tried 1st and 2nd method) only. It was registering events but none of the event is being identified by it. seems I have to add something additional for catching window events. Eg of Issue :- Form loads up, event handlers added up then but when I click on it nothing happens according to the click event handler. — AKS, Jul 27 '18 at 05:43
@user10122634 This sounds like a new question. If this answer has answered your question, then accept it. If the answer is useful, then upvote it. Post your current problem as a new question, together with the code you are using to register the form. — Zev Spitz, Jul 27 '18 at 05:48

Monitoring multiple forms from class library

1 Answers1

Allow constructor to take multiple Forms

Using a RegisterForm method

Using a CreateForm method

Using a base form

Allow constructor to take multiple `Form`s

Using a `RegisterForm` method

Using a `CreateForm` method