通過物業變更價值

Question

我有2種形式：表格A和表格B.我也有一個屬性字段類。

表單A包含我想在屬性發生更改時更改的標籤。表格B包含將改變屬性字段的代碼。

屬性類代碼：

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

形式B編碼：

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

形式A代碼：

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 
     } 

的屬性字段值被傳遞（這是我從在MessageBox知道），但它不會更新表單標籤本身的值。爲什麼是這樣？我究竟做錯了什麼？我也相信有一個更好的替代方案來實現ChangeMe（）方法的意圖實現 - 如果有的話，是否有任何建議？

Answer 1

在您的靜態方法ChangeMe中，您每次都要創建一個新窗體，您要更改該值。而不是你想改變現有表單的價值。因此，你的控制器需要這個FormA的實例。試着這樣說：

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(); 
      } 
     } 
    } 
} 

現在你鴕鳥政策需要是靜態的你FormA：

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

Answer 2

你可以做以下

1. 要定義一個委託
2. 實施財產變更通知

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); 
        } 
       } 
      } 
     } 
    } 
} 

在你的表格，當你啓動控制器對象

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** 
} 

上面的代碼將讓您對您的代碼有很大的控制，也會讓你的控制器代碼可重複使用和清潔。同樣 結果您可以通過實現INotifyPropertyChanged接口得到

INotifyPropertyChanged的

你可能會對這article看看以獲取更多信息