How do I make an Event in the Usercontrol and have it handled in the Main Form?

问题

I have a custom usercontrol and I want to do something relatively simple.

When ever a numeric up down in that usercontrol's value changes, have the main form update a display window.

This is not a problem if the NUD was not in a usercontrol but I can't seem to figure out how to have the event handled by the mainform and not the usercontrol.

回答1:

You need to create an event handler for the user control that is raised when an event from within the user control is fired. This will allow you to bubble the event up the chain so you can handle the event from the form.

When clicking Button1 on the UserControl, i'll fire Button1_Click which triggers UserControl_ButtonClick on the form:

User control:

public event EventHandler ButtonClick;

protected void Button1_Click(object sender, EventArgs e)
{
    //bubble the event up to the parent
    if (this.ButtonClick!= null)
        this.ButtonClick(this, e);               
}

Form:

UserControl1.ButtonClick += new EventHandler(UserControl_ButtonClick);

protected void UserControl_ButtonClick(object sender, EventArgs e)
{
    //handle the event 
}

回答2:

Try mapping it. Try placing this code in your UserControl:

public event EventHandler ValueChanged {
  add { numericUpDown1.ValueChanged += value; }
  remove { numericUpDown1.ValueChanged -= value; }
}

then your UserControl will have the ValueChanged event you normally see with the NumericUpDown control.

回答3:

you can do like this.....the below example shows text box(user control) value changed

   // Declare a delegate 
public delegate void ValueChangedEventHandler(object sender, ValueChangedEventArgs e);
public partial class SampleUserControl : TextBox 
{    
    public SampleUserControl() 
    { 
        InitializeComponent(); 
    }

    // Declare an event 
    public event ValueChangedEventHandler ValueChanged;

    protected virtual void OnValueChanged(ValueChangedEventArgs e) 
    { 
        if (ValueChanged != null) 
            ValueChanged(this,e); 
    }    
    private void SampleUserControl_TextChanged(object sender, EventArgs e) 
    { 
        TextBox tb  = (TextBox)sender; 
        int value; 
        if (!int.TryParse(tb.Text, out value)) 
            value = 0; 
        // Raise the event 
       OnValueChanged( new ValueChangedEventArgs(value)); 
    }    
}

回答4:

one of the easy way to do that is use landa function without any problem like

userControl_Material1.simpleButton4.Click += (s, ee) =>
            {
                Save_mat(mat_global);
            };

来源：https://stackoverflow.com/questions/7880850/how-do-i-make-an-event-in-the-usercontrol-and-have-it-handled-in-the-main-form

标签

winforms

user-controls

event-handling