Question

我有两种形式：表格A和表格B.我还有一个属性字段类。

表单A包含我想要在更改属性时更改的标签。表单B包含将更改属性字段的代码。

物业类代码：

 public class Controller
    {
        private static string _customerID;
        public static string customerID
        {
            get { return _customerID; }
            set
            {
                _customerID = value;
                if (_customerID != "")
                {
                    FormA.ChangeMe();
                }
            }
        }
    }

表格B代码：

    private void something_Click(object sender, SomethingEventArgs e) {
     Controller.customerID = "Cool";
}

表格A代码：

public static void ChangeMe()
        {
            var frmA = new FormA();
            MessageBox.Show("Test: " + Controller.customerID); //This works! Shows Cool
            frmA.lb2Change.Text = Controller.customerID; //This kind of works..
            MessageBox.Show("Test2: " + frmA.lb2Change.Text); //This shows the correct value. Shows Cool
        }

传递属性字段值（我从MessageBox中知道）但是它不会更新表单标签本身的值。为什么是这样？我究竟做错了什么？我也相信有更好的替代方法可以实现预期实现的ChangeMe（）方法 - 如果有任何建议的话？

Answer 1

您可以执行以下操作

定义代理
实施财产变更通知

<强>代表

public delegate void OnCustomerIDChanging(object sender,CancelEventArgs e);
public delegate void OnCustomerIDChanged(object sender,object value);
public class Controller
{
    private static string _customerID;
    public event OnCustomerIDChanging CustoerIDChanging;
    public event OnCustomerIDChanged CustoerIDChanged;
    public static string customerID
    {
        get { return _customerID; }
        set
        {
           // make sure that the value has a `value` and different from `_customerID`
           if(!string.IsNullOrEmpty(value) && _customerID!=value)
           {
               if(CustomerIDChanging!=null)
               {
                    var state = new CancelEventArgs();
                    // raise the event before changing and your code might reject the changes maybe due to violation of validation rule or something else
                    CustomerIDChanging(this,state);
                    // check if the code was not cancelled by the event from the from A
                    if(!state.Cancel)
                    {
                         // change the value and raise the event Changed
                         _customerID = value;
                         if(CustomerIDChanged!=null)
                             CustomerIDChanged(this,value);
                    }
               }
           }
        }
    }
}

var controller = new Controller();
controller.CustomerIDChanging +=(sd,args) =>{
     // here you can test if you want really to change the value or not
     // in case you want to reject the changes you can apply 
     args.Cancel = true;
};
controller.CustomerIDChanged +=(sd,args) =>{

     // here you implement the code **Changed already**
}

上面的代码可以让您很好地控制代码，也可以使您的控制器代码可重用和清理。相同您可以通过实施INotifyPropertyChanged接口
来获得结果

<强> INotifyPropertyChanged的

您可以查看此article以获取更多信息

Answer 2

在静态方法ChangeMe中，每次都要创建一个新表单，要更改值。而不是你想要改变现有表格的价值。因此，您的Controller需要此FormA的实例。试试这样：

public class Controller
{
    //You can pass the form throught the constructor,
    //create it in constructor, ...
    private FormA frmA;

    private string _customerID;
    public string customerID
    {
        get { return _customerID; }
        set
        {
            _customerID = value;
            if (_customerID != "")
            {
                frmA.ChangeMe();
            }
        }
    }
}

现在您不需要在FormA：

中保持静态

public void ChangeMe()
{
    MessageBox.Show("Test: " + Controller.customerID);
    this.lb2Change.Text = Controller.customerID;
}

物业变化传递价值

2 个答案: