按钮IsEnabled永远不会改变

5 回答

• -1

  IsSearchCriteriaHasValue 需要引发一个更改的事件，您可以使用 INotifyPropertyChanged 接口执行此操作：

  public class Customer : INotifyPropertyChanged
  {
      // INotifyPropertyChanged members
      public event PropertyChangedEventHandler PropertyChanged;
  
      public void OnPropertyChanged(PropertyChangedEventArgs e)
      {
          if (PropertyChanged != null)
          {
              PropertyChanged(this, e);
          }
      }
  
      // Your property
      private string _Name;
  
      public string Name
      {
          get
          {
              return _Name;
          }
          set
          {
             _Name = value;
             OnPropertyChanged(new PropertyChangedEventArgs("Name"));
          }
      }
  }
  

  回复于 2024-05-06T03:53:49+08:00
• 2

  您可以为按钮编写触发器（SearchBox看起来像UI控件）

  <Style TargetType =“Button”>

  <Setter Property =“IsEnabled”Value =“True”/>
  <Style.Triggers>
  <DataTrigger Binding =“{Binding Selection.Count，ElementName = SearchBox}”Value =“0”>！ - 您也可以使用convertor
  <Setter Property =“IsEnabled”Value =“False”/>
  </ DataTrigger>
  </Style.Triggers>
  </ Style> </Button.Style> </ Button>

  回复于 2024-05-06T03:53:49+08:00
• 1

  它与XAML没有问题，它的通知问题 . 我希望你知道INotifyProperty接口的NotifyPropertyChanged事件 . 只有在ViewModel中为属性触发了该属性，UI才会获取通知并对其进行更新 .

  如果SearchBox.Selection计数发生更改，它不会触发任何IsSearchCriteriaHasValue属性的通知，表明它已被更改并且UI应该更新 .

  让我们说SearchBox.Selection绑定到observableCollection并且集合发生变化，然后订阅observableCollection以进行添加/删除然后触发 NotifyPropertyChanged("IsSearchCriteriaHasValue") ;那里 .

  回复于 2024-05-06T03:53:49+08:00
• 7

  绑定适用于属性更改事件 . 您的 ViewModel 应该实现 INotifyPropertyChanged 接口 .

  https://msdn.microsoft.com/en-us/library/system.componentmodel.inotifypropertychanged(v=vs.110).aspx

  一个例子：

  // This form demonstrates using a BindingSource to bind 
  // a list to a DataGridView control. The list does not 
  // raise change notifications. However the DemoCustomer type  
  // in the list does. 
  public partial class Form1 : Form
  {
      // This button causes the value of a list element to be changed. 
      private Button changeItemBtn = new Button();
  
      // This DataGridView control displays the contents of the list. 
      private DataGridView customersDataGridView = new DataGridView();
  
      // This BindingSource binds the list to the DataGridView control. 
      private BindingSource customersBindingSource = new BindingSource();
  
      public Form1()
      {
          InitializeComponent();
  
          // Set up the "Change Item" button.
          this.changeItemBtn.Text = "Change Item";
          this.changeItemBtn.Dock = DockStyle.Bottom;
          this.changeItemBtn.Click +=
              new EventHandler(changeItemBtn_Click);
          this.Controls.Add(this.changeItemBtn);
  
          // Set up the DataGridView.
          customersDataGridView.Dock = DockStyle.Top;
          this.Controls.Add(customersDataGridView);
  
          this.Size = new Size(400, 200);
      }
  
      private void Form1_Load(object sender, EventArgs e)
      {
          // Create and populate the list of DemoCustomer objects 
          // which will supply data to the DataGridView.
          BindingList<DemoCustomer> customerList = new BindingList<DemoCustomer>();
          customerList.Add(DemoCustomer.CreateNewCustomer());
          customerList.Add(DemoCustomer.CreateNewCustomer());
          customerList.Add(DemoCustomer.CreateNewCustomer());
  
          // Bind the list to the BindingSource. 
          this.customersBindingSource.DataSource = customerList;
  
          // Attach the BindingSource to the DataGridView. 
          this.customersDataGridView.DataSource =
              this.customersBindingSource;
  
      }
  
      // Change the value of the CompanyName property for the first  
      // item in the list when the "Change Item" button is clicked.
      void changeItemBtn_Click(object sender, EventArgs e)
      {
          // Get a reference to the list from the BindingSource.
          BindingList<DemoCustomer> customerList =
              this.customersBindingSource.DataSource as BindingList<DemoCustomer>;
  
          // Change the value of the CompanyName property for the  
          // first item in the list.
          customerList[0].CustomerName = "Tailspin Toys";
          customerList[0].PhoneNumber = "(708)555-0150";
      }
  
  }
  
  // This is a simple customer class that  
  // implements the IPropertyChange interface. 
  public class DemoCustomer : INotifyPropertyChanged
  {
      // These fields hold the values for the public properties. 
      private Guid idValue = Guid.NewGuid();
      private string customerNameValue = String.Empty;
      private string phoneNumberValue = String.Empty;
  
      public event PropertyChangedEventHandler PropertyChanged;
  
      // This method is called by the Set accessor of each property. 
      // The CallerMemberName attribute that is applied to the optional propertyName 
      // parameter causes the property name of the caller to be substituted as an argument. 
      private void NotifyPropertyChanged([CallerMemberName] String propertyName = "")
      {
          if (PropertyChanged != null)
          {
              PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
          }
      }
  
      // The constructor is private to enforce the factory pattern. 
      private DemoCustomer()
      {
          customerNameValue = "Customer";
          phoneNumberValue = "(312)555-0100";
      }
  
      // This is the public factory method. 
      public static DemoCustomer CreateNewCustomer()
      {
          return new DemoCustomer();
      }
  
      // This property represents an ID, suitable 
      // for use as a primary key in a database. 
      public Guid ID
      {
          get
          {
              return this.idValue;
          }
      }
  
      public string CustomerName
      {
          get
          {
              return this.customerNameValue;
          }
  
          set
          {
              if (value != this.customerNameValue)
              {
                  this.customerNameValue = value;
                  NotifyPropertyChanged();
              }
          }
      }
  
      public string PhoneNumber
      {
          get
          {
              return this.phoneNumberValue;
          }
  
          set
          {
              if (value != this.phoneNumberValue)
              {
                  this.phoneNumberValue = value;
                  NotifyPropertyChanged();
              }
          }
      }
  }
  

  }

  回复于 2024-05-06T03:53:49+08:00
• 1

  绑定适用于属性更改事件 . 您的ViewModel应该实现 INotifyPropertyChanged 接口 . 而且你需要在属性集中提升属性更改事件 . 或者只需在CanExecute方法中使用 delegate command 并写入启用禁用逻辑 . 请参阅此链接了解更多信息http://www.codeproject.com/Questions/179129/MVVM-Enable-Disable-button-via-a-PropertyChanged-e

  回复于 2024-05-06T03:53:49+08:00