Create custom wpf event

问题

i've created an UserControl for Database connection where user input Username and Password for a connection. This UserControl is in a MainWindow.xaml

Now, in code behind of my UserControl i create a MSSQL connection. If login Successfully, i want to Raise a custom event to expose in MainWindow.

For example in MyUserControl.xaml.cs

try
{

    using (SqlConnection sqlConn = new SqlConnection(connection))
    {
        sqlConn.Open();
        MessageBox.Show("Connessione Riuscita!", "Connessione a " + TextIP.Text, MessageBoxButton.OK, MessageBoxImage.Information);
        RaiseMyEvent();
        sqlConn.Close();                 
    }
}
catch (SqlException ex)
{
    MessageBox.Show("Connessione Fallita: " + ex.Message, "Connessione a " + TextIP.Text, MessageBoxButton.OK, MessageBoxImage.Error);
}

and In MainWindow.xaml i want to use mypersonalized event:

<Window x:Class="XLogin.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="350" Width="525"
        xmlns:local="clr-namespace:XLogin" WindowStartupLocation="CenterScreen">
    <Grid>
        <local:DBLogin x:Name="DBLoginFrame" MyPersonalizedUCEvent="DBLoginFrame_MyPersonalizedUCEvent"/>
    </Grid>
</Window>

I need this for multiple type connection (MSSQL, Oracle, MySql etc).

How to get this?

回答1:

First you should define a delegate and then use that delegate to define that event.

In your MyUserControl.xaml.cs file add the following

Option 1

    public delegate void MyPersonalizedUCEventHandler(string sampleParam);

    public event MyPersonalizedUCEventHandler MyPersonalizedUCEvent;

    public void RaiseMyEvent()
    {
        // Your logic
        if (MyPersonalizedUCEvent != null)
        {
            MyPersonalizedUCEvent("sample parameter");
        }
    }

And that's it. You have defined your event.

Option 2

    public event Action<String> MyPersonalizedUCEvent;

    public void RaiseMyEvent()
    {
        // Your logic
        if (MyPersonalizedUCEvent != null)
        {
            MyPersonalizedUCEvent("sample parameter");
        }
    }

More about the Action delegate can be found in this link.

Note:

In many cases if events are not used properly they can cause memory leaks. Just make sure that you have written code to remove the registered event handlers as shown below.

        MyPersonalizedUCEvent -= MyPersonalizedUCEventHandler;

回答2:

First create a public event in your class :

public event EventHandler<MyEventArgs> SomethingChanged;

NB MyEventArgs is the type of object that will be passed with the event to subscribers. For this example it could be like this :

public class MyEventArgs{
    public String Prop1 {get; set;}
}

Next fire it as-is in your class :

SomethingChanged?.Invoke(this, new MyEventArgs() { Prop1="test" });

Finnally handle it like this :

private void OnSomethingChanged(object sender, MyEventArgs e)
{
    //TODO
}

NB You need to subscribe to the event in order to enter in the OnSometingChanged method. Subscribe like this :

myClass.SomethingChanged+=OnSomethingChanged;

Where myClass is an instance of the class where you define SomethingChanged

来源：https://stackoverflow.com/questions/14500559/create-custom-wpf-event

标签

wpf

xaml

events

custom-event