C＃PictureBox.Image的DataBind到物體圖像物業

Question

我定義爲這個

public class Employee : INotifyPropertyChanged 
{ 
    private Image photo; 


    public Image Photo 
    { 
      get { return photo; } 
      set { photo = value; InvokePropertyChanged(new PropertyChangedEventArgs("Photo")); } 
    } 


    #region Implementation of INotifyPropertyChanged 

    public event PropertyChangedEventHandler PropertyChanged; 

    public void InvokePropertyChanged(PropertyChangedEventArgs e) 
    { 
     PropertyChangedEventHandler handler = PropertyChanged; 
     if (handler != null) handler(this, e); 
    } 

    #endregion 

} 

類Employee這是我的用法：我已經命名爲pbPhoto和圖片一個PictureBox控制有默認值從我的Resources.Blank，該屬性是事件內的Employee.Photo屬性的數據綁定。

Employee employee = new Employee(); 
this.pbPhoto.DataBindings.Add("Image", employee, "Photo"); 

但它似乎不工作，我得到了這個錯誤信息。

無法將值格式化爲所需的類型。

Answer 1

我只是解決基於以上Mono's comment這個問題，

有兩種不同的方法：

首先，結合pbPhoto.Image財產爲對象Photo屬性之前，你有一個默認值分配給employee.Photo因爲我們不能設置一個綁定屬性它返回一個null值。

Employee employee = new Employee(); 
employee.Photo = Resources.Blank; // Initial value. 
this.pbPhoto.DataBindings.Add("Image", employee, "Photo"); 

另一種是設定在Employee構造Photo屬性的初始值。

public Employee() 
{ 
    this.Photo = Resources.Blank; 
} 

然後你可以繼續這個。

// During the program execution the Photo has an initial assigned value. 
Employee employee = new Employee(); 
this.pbPhoto.DataBindings.Add("Image", employee, "Photo"); 

Answer 2

這是通過一個非常古老的WinForms數據綁定錯誤行爲其由Binding.FormattingEnabled屬性設置爲true固定引起的（不幸的是，「向後兼容」默認爲false）：

this.pbPhoto.DataBindings.Add("Image", employee, "Photo", true); 

如果要默認值時，數據源屬性爲null關聯，則可以使用Binding.NullValue屬性：

this.pbPhoto.DataBindings.Add("Image", employee, "Photo", true, 
    DataSourceUpdateMode.OnValidation, Resources.Blank);