C#中事件的使用

定义一个事件类型

public class PropertyValueChangedEventArgs : EventArgs
    {
        private string _propertyName;
        private object _oldValue;
        private object _newValue;

        public PropertyValueChangedEventArgs()
            : base()
        { }

        public PropertyValueChangedEventArgs(string propertyName, object oldValue, object newValue)
            : base()
        {
            _propertyName = propertyName;
            _oldValue = oldValue;
            _newValue = newValue;
        }

        public string PropertyName
        {
            get { return _propertyName; }
            set { _propertyName = value; }
        }

        public object OldValue
        {
            get { return _oldValue; }
            set { _oldValue = value; }
        }

        public object NewValue
        {
            get { return _newValue; }
            set { _newValue = value; }
        }
    }

定义一个事件测试使用的类

public class TestPropertyValueChangedEventArgs 
    {
        private static readonly object uniqueLock = new object();
        private static TestPropertyValueChangedEventArgs _Instance = null;
        public static TestPropertyValueChangedEventArgs Instance
        {
            get
            {
                lock (uniqueLock)
                {
                    if (_Instance == null)
                    {
                        _Instance = new TestPropertyValueChangedEventArgs();
                    }
                }
                return _Instance;
            }

        }


        public event EventHandler<PropertyValueChangedEventArgs> PropertyChanged;
        private void OnPropertyChanged(string aPropertyName, object aOldValue, object aNewValue)
        {
            PropertyValueChangedEventArgs e = new PropertyValueChangedEventArgs(aPropertyName, aOldValue, aNewValue);
            if (PropertyChanged != null)
            {
                PropertyChanged(this, e);
            }
        }

        public void SetString(string strOldString, string strNewString)
        {
            OnPropertyChanged("Test_SetString", strOldString, strNewString);
        }
    }

注册事件

TestPropertyValueChangedEventArgs.Instance.PropertyChanged += new EventHandler<PropertyValueChangedEventArgs>(PropertyChanged);

使用事件

private void button2_Click(object sender, EventArgs e)
        {
            Thread thread = new Thread(
                () =>
                {
                    TestPropertyValueChangedEventArgs.Instance.SetString("_OLD2", "_NEW2");
                }
              );

            thread.Start();
        }

        private void PropertyChanged(object sender, PropertyValueChangedEventArgs e)
        {
            if (e.PropertyName == "Test_SetString")
            {
                this.txtLog.Text += "收到设置属性Test_SetString事件，设置内容为:" + e.NewValue + "\n";
            }
        }