Accessing Components of One Form From Another

[l3mon]

So have two forms under the same namespace and I need to be able to access a richtextbox attached to the form "Home" from the form "Editor". But whenever I try to access it it doesn't come up, I'm new to C# but I'm assuming this is from the public/private modifiers. Also, "Home" is the MdiParent of "Editor" if that makes a difference. So what I'm trying to do is like.

Home.richtextbox.Text = "Editor Running"; 
 

Any help would be greatly appreciated.

[tlhintoq]

Just a suggestion...

Don't access controls directly like that. It's much better to raise an event that the other form is subscribed to.

If your "Editor" raises an event like CurrentModeEvent(new ModeArgs("Running"));

Then you could have 1 or a dozen tools, forms, controls subscribed to that event. They all react at the same time. Yes your Editor form is not tightly tied to the other forms.

Right now it might be only one form that listens to Editor so it doesn't seem like a big deal. But later you add a toolboxpallet... then you add another form...

[l3mon]

I'm sorry... I'm really not that good with this. I have multiple forms that will be children of the "Home" form (such as the editor form) and the only part of the "Home" form I want to affect is a richtextbox similar to the output box under View->Output (in Visual c#). So it's showing the collective output/debug infostuffs of all the forms. I'm not really following you. Just how is it possible to get to the form or at least a method on it which I could use to update the status box.

[tlhintoq]

In that case you REALLY don't want to be accessing your 'Output" richtextform directly from a bunch of other forms. It just makes it a mess to maintain.

You want to make a custom event that your Output window listens for. Whenever it hears the event it reacts by putting the text of the eventarg into the richtext box.

Think of your program as a bingo parlor. The events are the man picking the numbers. He just yells out N-15 and all the players hear him and respond by checking the bingo cards. The players all subscribe to the event of:
Caller.yells(PickedNumber);

The caller doesn't know anything about the players or their game cards. He has one job, yell the numbers. It doesn't matter if 1 person is playing or 100.

I suggest you first make a generic form with all your custom but commonly shared code it in. This form will have a custom event something like "LogThis" or "ReportThis"

Now when you make all of your other children forms, make them inherit from that common form that already has the event. This way *they* inherit that event.

When your Mainform makes newforms it can do something like this...

MyCustomForm child1 = new MyCustomForm();
child1.LogThis += new LogThis(LogThisMethodHandler);
 
MyCustomForm child2 = new MyCustomForm();
child2.LogThis += new LogThis(LogThisMethodHandler);
 
MyCustomForm child3 = new MyCustomForm();
child3.LogThis += new LogThis(LogThisMethodHandler);
 

Now you have 3 new child forms, all inherited from the custom form with the LogThis Event. Your MainForm is subscribed to each child's LogThis event.

When a child yells "LogThis" the parent responds in the LogThisMethodHandler method.

The children only know they need to yell "LogThis". They don't know *how* the parent is going to log it. They don't have to. They are children. Its not their place to tell the parent how to react.

The parent has one reaction to all the children: It logs when they yell.
If you later change your logging to include writing to file in addition to displaying in the richtextbox you only have to make the update in the one method of the parent - not in all the child forms.

[l3mon]

Thank you, now I know what to do just not how.
This is one of the childforms being created.

private void hashCalculatorToolStripMenuItem_Click(object sender, EventArgs e)
 {
      Form HashCalc = new HashCalc();
      HashCalc.MdiParent = this;
      HashCalc.Show();
}
 

Here is the method I want to use on the mainform to update the richtextbox

 public void addStatus(string status)
 {
      RtDebug.Text += "\n" + status;
      RtDebug.Select(RtDebug.Text.Length + 1, 2);
      RtDebug.ScrollToCaret();
 }
 

So how would I define the custom event and have it pass the "status" argument? And how do I "shout" from a child form?

[tlhintoq]

I was actually thinking about writing an "Insights" article on the subject. Much better to have that much info in an article than a single post.

In the mean time Google for "C# custom event" and you will find a ton of articles and how-to blogs on the topic.

[l3mon]

I tried that before posting... but, whatever. Thanks for pointing me in the right direction.

[l3mon]

Wait, I got it. I was defining the delegate and the event in the wrong class/form But thanks again! :)

[tlhintoq]

I was checking our own site before starting an article on events and guess what? Frinavale already did one.

Amazing what you can find when you look
http://bytes.com/topic/net/insights/...use-events-net

[tlhintoq]

@l3mon
Yah know... you can eliminate that whole delegate thing too. EventHandler already has its own delegate, so why re-create it? I tend to do my events short and sweet.

I have a namespace I use in all my projects that keeps all my common stuff, like eventargs, registry reading classes and so on. So that's where I keep things like a text args etc.

namespace tlhintoq
{
    public class TextArgs : EventArgs
    {
        private string szMessage;
        public string Message
        {
            get { return szMessage; }
            set { szMessage = value; }
        }
 
        public TextArgs(string TextMessage)
        {
            szMessage = TextMessage;
        }
    }
}
 

Making the event is then a single line of code.
I use a method to raise the event for safety and convenience sake, and it is only 5 lines if you count the curly braces.

    public partial class MyForm1 : Form
    {
        public event EventHandler<tlhintoq.TextArgs> LogMessage;
        public void RaiseLog(string Message)
        {
            EventHandler<tlhintoq.TextArgs> temp = LogMessage;
            if (temp != null) temp(null, new tlhintoq.TextArgs(Message));
        }
 
 
        void SomeOtherMethod()
        {
            //  Do a bunch of stuff
 
 
           // Raise the event that will create a log entry
           RaiseLog("SomeOtherMethod completed successfully");
        }
   }