值更改事件处理程序 [英] value changed eventhandler
本文介绍了值更改事件处理程序的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
这样的东西(真正的抽象):
value.Changed + = new Eventhandler(valuechanged);
private void valuechanged(object sender,eventargs e)
{
list [e.Oldvalue] - = some eventhandler;
list [e.newValue] + = some eventhanlder;
}
谢谢。
解决方案
你可以这样做:
class ValueChangedEventArgs:EventArgs
{
public readonly int LastValue;
public readonly int NewValue;
public ValueChangedEventArgs(int LastValue,int NewValue)
{
this.LastValue = LastValue;
this.NewValue = NewValue;
}
}
类值
{
public Values(int InitialValue)
{
_value = InitialValue;
}
public event EventHandler< ValueChangedEventArgs>的ValueChanged;
protected virtual void OnValueChanged(ValueChangedEventArgs e)
{
if(ValueChanged!= null)
ValueChanged(this,e);
}
private int _value;
public int Value
{
get {return _value; }
set
{
int oldValue = _value;
_value = value;
OnValueChanged(new ValueChangedEventArgs(oldValue,_value));
}
}
}
所以你可以使用你的课像这样(控制台测试):
void Main()
{
值test = new Values(10);
test.ValueChanged + = _ValueChanged;
test.Value = 100;
test.Value = 1000;
test.Value = 2000;
}
void _ValueChanged(object sender,ValueChangedEventArgs e)
{
Console.WriteLine(e.LastValue.ToString());
Console.WriteLine(e.NewValue.ToString());
}
这将打印:
最后价值:10
新值:100
最终价值:100
新值:1000
最后价值:1000
新值:2000
I want to react, whenever an integer value has changed. So, is there a possibility to write an own eventhandler? I need to get the old value and the new one, because I have to de-reference some events for an object in a list with the index of the old value and reference these events to the listitem with the index of the new value.
Something like this (really abstract):
value.Changed += new Eventhandler(valuechanged);
private void valuechanged(object sender, eventargs e)
{
list[e.Oldvalue] -= some eventhandler;
list[e.newValue] += some eventhanlder;
}
Thanks.
解决方案
You can do something like this:
class ValueChangedEventArgs : EventArgs
{
public readonly int LastValue;
public readonly int NewValue;
public ValueChangedEventArgs(int LastValue, int NewValue)
{
this.LastValue = LastValue;
this.NewValue = NewValue;
}
}
class Values
{
public Values(int InitialValue)
{
_value = InitialValue;
}
public event EventHandler<ValueChangedEventArgs> ValueChanged;
protected virtual void OnValueChanged(ValueChangedEventArgs e)
{
if(ValueChanged != null)
ValueChanged(this, e);
}
private int _value;
public int Value
{
get { return _value; }
set
{
int oldValue = _value;
_value = value;
OnValueChanged(new ValueChangedEventArgs(oldValue, _value));
}
}
}
So you can use your class like here (Console Test):
void Main()
{
Values test = new Values(10);
test.ValueChanged += _ValueChanged;
test.Value = 100;
test.Value = 1000;
test.Value = 2000;
}
void _ValueChanged(object sender, ValueChangedEventArgs e)
{
Console.WriteLine(e.LastValue.ToString());
Console.WriteLine(e.NewValue.ToString());
}
This will print:
Last Value: 10
New Value: 100
Last Value: 100
New Value: 1000
Last Value: 1000
New Value: 2000
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