C＃父窗体未从子目录更新

Question

I have two Forms Parent Form : properties : Total Value. Button to load child form. Child Form: property : insert Value.

When I run application, Parent form loaded first. I can load second (Child) form by click button. Problem is that when I insert value in child form parent form is not showing any changes even I pass value by delegate and other methods.

I don't want to reload Parent Window. Please help

Answer 1

What you should be doing is creating events on the child for (or using the existing events if they will do the job) and having the parent form subscribe to those events.

One common example is to have the parent hide itself, show the child, and then show itself again when the child is closed. Here is some code that does that:

//in parent form
private void someButtonClickHander(object sender, EventArgs args)
{
  ChildForm child = new ChildForm();
  this.Hide();

  child.Closing += (sender2, args2) => 
  {
    var someResultFromChildForm = child.SomePropertyOnChildForm;
    this.Show();
  }

  child.Show();
}

If the closing event doesn't work for you (maybe you want to do something when the child form presses a button) you may need to have the child create it's own event. There are lots of tutorials on MSDN or other sites on how to do this. If you have trouble with that (or any other aspect of this design) please ask for clarifications in comments.

Answer 2

If you want to keep data consistent between multiple forms, I recommend putting the data into an object that you can reach from both forms.

The most direct way is to implement INotifyPropertyChanged for the object, so you can bind to this object in both forms and any changes made will trigger the property change event.

For more complex scenarios I make an object that has custom events that I can subscribe to, as INotifyPropertyChanged can be lack the subtlety needed in complex scenarios. As an example, I have a "Helm" object for my primary navigation form that all of the UI elements subscribe to. If a navigation event occurs, the helm does all of the navigation and data loading, and then it triggers a series of events that the UI listens to.

For a simple parent child this can seem like overkill, but this model (having one truth for the current state that the UI simply subscribes to) allows your UI to evolve and for each element of the UI to only worry about its own needs.

Answer 3

Have a Property called Parent in your child form. When you create the instance of the Child,Pass the current object( parent form object) to the constructor where you will set it as the Parent property value of child. In Parent form Have a Public Method in your Parent form. P

parent form

Form1 : Form
{    
    decimal _totalPrice;

    public void UpdateTotal(decimal val)
    {
      _totalPrice=_totalPrice+val;
      lblTotal.Text=_totalPrice.ToString();
    }    
}

Child Form

Form2:Form
{
  public Form1 Parent { set;get;}
  public Form2(Parent parent) 
  { 
    this.Parent =parent;
  }    
}

When creating the object of Child form

Form2 objChjild=new Child(this);
//do whatever

Now from child form, if you want to update the total,

call like this

this.Parent.UpdateTotal(200);