用户控件事件处理程序订阅

Question

I have a windows forms app with a user control. I'm trying to get the UC to call a function on the main form, but when I add the UC, the main form can't see the public event.

My UC looks like this:

public partial class uctlLogin: UserControl
{
    public delegate void ButtonClickedEventHandler(object sender, EventArgs e);
    public event ButtonClickedEventHandler OnUserControlButtonClicked;

    public uctlLogin()
    {
        InitializeComponent();
        btnLogin.Click += new EventHandler(OnButtonClicked);
    }

    private void OnButtonClicked(object sender, EventArgs e)
    {
        if (OnUserControlButtonClicked != null)
            OnUserControlButtonClicked(this, e);
    }
}

My form code is:

public partial class frmMain : Form
{
    UserControl uctlLogin1 = new TabletUserControls.uctlLogin();

    public frmMain()
    {
        InitializeComponent();
        uctlLogin1.OnUserControlButtonClicked += new EventHandler(OnUCButtonClicked);
    }

    private void OnUCButtonClicked(object sender, EventArgs e)
    {
        MessageBox.Show("Horray!");
    }

    private void frmMain_Load(object sender, EventArgs e)
    {
        this.Controls.Add(uctlLogin1);

    }
}

The problem is in this line:

uctlLogin1.OnUserControlButtonClicked += new EventHandler(OnUCButtonClicked);

Generates the following message:

'System.Windows.Forms.UserControl' does not contain a definition for 'OnUserControlButtonClicked' and no extension method 'OnUserControlButtonClicked' accepting a first argument of type 'System.Windows.Forms.UserControl' could be found (are you missing a using directive or an assembly reference?)

I've tried putting the UC in the same project and creating the UC in a separate project, then adding a reference to it. After Googling for hours, I'm stuck. Any idea what I'm missing here?

BTW, I'm using VS2012 targeting the .Net Framework 4.5.

Answer 1

That's because in your frmMain , you declared uctlLogin1 as UserControl , rather than uctlLogin . The type UserControl doesn't have a OnUserControlButtonClicked event, and the compiler doesn't know that uctlLogin1 is an instance of uctlLogin , since you declared it as UserControl . Just specify the actual type of uctlLogin1 and it will work fine.