SilverLight Tip 1 : Validation

1：SL的数据验证和WPF的不同

首先，很遗憾，SL中不再存在ValidationRules，要在SL中绑定时验证数据，并且显示在UI，只能依赖于NotifyOnValidationError=True, ValidatesOnExceptions=True这两个属性，如下：

如果要查看WPF的数据验证的方式，可以查看该文《WPF快速指导5：验证》。

2：一般情况下的验证

一般情况下，UI绑定数据类型的属性，如在上图中，绑定的就是Name和Age，它在UI的VIEWMODEL中，如下：

public class MainPageVM : INotifyPropertyChanged
{
    public MainPageVM()
    {
    }
 
    private string name = "luminji";
 
    public string Name
    {
        get { return name; }
        set
        {
            if (string.IsNullOrEmpty(value))
            {
                throw new Exception("姓名不能为空");
            }
            name = value;
            OnPropertyChanged("Name");
        }
    }
 
    private int age = 1;
 
    public int Age
    {
        get { return age; }
        set
        {
            if (value > 100)
            {
                throw new Exception("年龄必须小与100");
            }
            age = value;
            OnPropertyChanged("Age");
        }
    }
 
    public event PropertyChangedEventHandler PropertyChanged;
 
    protected virtual void OnPropertyChanged(string propertyName)
    {
        PropertyChangedEventHandler pceh = PropertyChanged;
        if (pceh != null)
        {
            pceh(this, new PropertyChangedEventArgs(propertyName));
        }
    }
    
}

采用UI直接绑定VM的属性，如果Age>100，则UI会提示出现输入有误。

3：绑定实体类型

不过，如果属性很多，我们就会考虑绑定实体类型。如User，而这个实体类，是在服务器端的，形如：

public class User
{
    private string name = "luminji";
 
    public string Name
    {
        get { return name; }
        set
        {
            name = value;
        }
    }
 
    private int age = 1;
 
    public int Age
    {
        get { return age; }
        set
        {
            age = value;
        }
    }
}

比如，我们使用的是Ria Service。Ria Service有可能是从DAL层获取数据并开放接口给客户端。我们都知道，客户端的代码都是自动生成的，自动生成的代码在SL项目的Generated_Code目录下的（SL项目名）.Web.g.cs文件下。所以，最终User类型在客户端的代理形式为：

/// <summary>
/// The 'User' entity class.
/// </summary>
[DataContract(Namespace="http://schemas.datacontract.org/2004/07/SilverlightApplication3.Web.Model")]
public sealed partial class User : Entity
{
     
    private int _age;
     
    private string _name;
     
    #region Extensibility Method Definitions
 
    /// <summary>
    /// This method is invoked from the constructor once initialization is complete and
    /// can be used for further object setup.
    /// </summary>
    partial void OnCreated();
    partial void OnAgeChanging(int value);
    partial void OnAgeChanged();
    partial void OnNameChanging(string value);
    partial void OnNameChanged();
 
    #endregion
     
     
    /// <summary>
    /// Initializes a new instance of the <see cref="User"/> class.
    /// </summary>
    public User()
    {
        this.OnCreated();
    }
     
    /// <summary>
    /// Gets or sets the 'Age' value.
    /// </summary>
    [DataMember()]
    public int Age
    {
        get
        {
            return this._age;
        }
        set
        {
            if ((this._age != value))
            {
                this.OnAgeChanging(value);
                this.RaiseDataMemberChanging("Age");
                this.ValidateProperty("Age", value);
                this._age = value;
                this.RaiseDataMemberChanged("Age");
                this.OnAgeChanged();
            }
        }
    }
     
    /// <summary>
    /// Gets or sets the 'Name' value.
    /// </summary>
    [DataMember()]
    [Editable(false, AllowInitialValue=true)]
    [Key()]
    [RoundtripOriginal()]
    public string Name
    {
        get
        {
            return this._name;
        }
        set
        {
            if ((this._name != value))
            {
                this.OnNameChanging(value);
                this.ValidateProperty("Name", value);
                this._name = value;
                this.RaisePropertyChanged("Name");
                this.OnNameChanged();
            }
        }
    }
     
    /// <summary>
    /// Computes a value from the key fields that uniquely identifies this entity instance.
    /// </summary>
    /// <returns>An object instance that uniquely identifies this entity instance.</returns>
    public override object GetIdentity()
    {
        return this._name;
    }
}

这个时候，如果我们在UI中继续绑定这个实体类型，势必会丢掉UI异常通知的行为，因为，显然，我们不能跑到这个客户端的代理类中throw new Exception("姓名不能为空"); ，那会在下一次代码自动生成的时候被覆盖掉。

4：解决方案之建立映射

一种解决方案是我们的UI仍旧不绑定实体类型，而是为类型的属性在ViewModel中建立一一映射的关系，如下：

public class MainPageVM : INotifyPropertyChanged
{
    public MainPageVM()
    {
        user = new User();
        serviceUser = new DomainServiceUser();
        serviceUser.Load<User>(serviceUser.GetAUserQuery(), new Action<System.ServiceModel.DomainServices.Client.LoadOperation<User>>(this.GetAUserCallBack), null);
    }
 
    DomainServiceUser serviceUser;
    User user;
     
     
    void GetAUserCallBack(LoadOperation<User> arg)
    {
        user = (arg.Entities as IList<User>)[0];
        Name = user.Name;
        Age = user.Age;
    }
 
 
    public string Name
    {
        get { return user.Name; }
        set
        {
            if (string.IsNullOrEmpty(value))
            {
                throw new Exception("姓名不能为空");
            }
            user.Name = value;
            OnPropertyChanged("Name");
        }
    }
 
 
    public int Age
    {
        get { return user.Age; }
        set
        {
            if (value > 100)
            {
                throw new Exception("年龄必须小与100");
            }
            user.Age = value;
            OnPropertyChanged("Age");
        }
    }
 
    public event PropertyChangedEventHandler PropertyChanged;
 
    protected virtual void OnPropertyChanged(string propertyName)
    {
        PropertyChangedEventHandler pceh = PropertyChanged;
        if (pceh != null)
        {
            pceh(this, new PropertyChangedEventArgs(propertyName));
        }
    }
    
}

UI效果图：

到此位置的源码下载为：SilverlightApplication20110618.zip

5：解决方案之使用ValidationSummary

使用ValidationSummary，需要我们引入程序集System.Windows.Controls.Data.Input，在UI前台，我们需要安置一个ValidationSummary：

接着，我们让前台的ValidationSummary的Errors赋值给VM。

public partial class MainPage : UserControl
{
    public MainPage()
    {
        InitializeComponent();
        ViewModel = new MainPageVM(this.vs.Errors);
    }
 
    public MainPageVM ViewModel
    {
        get
        {
            return (MainPageVM)this.DataContext;
        }
        set
        {
            this.DataContext = value;
        }
    }
 
    private void btnSave_Click(object sender, RoutedEventArgs e)
    {
 
    }
}

我们还需要为UI绑定一些Command，以便在需要验证输入的时候，让VM去判断是否有错误发生。一旦有错误发生，则为Errors添加错误项。

public class MainPageVM : INotifyPropertyChanged
{
    public MainPageVM(ObservableCollection<ValidationSummaryItem> errors)
    {
        m_errors = errors;
        Click = new ActionCommand(this.OnClick);
        serviceUser = new DomainServiceUser();
        serviceUser.Load<User>(serviceUser.GetAUserQuery(), new Action<System.ServiceModel.DomainServices.Client.LoadOperation<User>>(this.GetAUserCallBack), null);
        //serviceUser.Load<User>(serviceUser.GetAUserQuery(), LoadBehavior.RefreshCurrent, new Action<System.ServiceModel.DomainServices.Client.LoadOperation<User>>(this.GetAUserCallBack), null);
    }
 
    DomainServiceUser serviceUser;
    User user;
    ObservableCollection<ValidationSummaryItem> m_errors;
 
    void GetAUserCallBack(LoadOperation<User> arg)
    {
        user = (arg.Entities as IList<User>)[0];
        OnPropertyChanged("User");
    }
 
    public User User
    {
        get { return user; }
        set
        {
            user = value;
            OnPropertyChanged("User");
        }
    }
 
    public ICommand Click { get; private set; }
 
    public void OnClick(object arg)
    {
        m_errors.Clear();
        if (User.Age > 100)
        {
            m_errors.Add(new ValidationSummaryItem("年龄不能大雨100"));
        }
    }
 
    public event PropertyChangedEventHandler PropertyChanged;
 
    protected virtual void OnPropertyChanged(string propertyName)
    {
        PropertyChangedEventHandler pceh = PropertyChanged;
        if (pceh != null)
        {
            pceh(this, new PropertyChangedEventArgs(propertyName));
        }
    }
 
}

最后的运行结果为：

备注：要让实体类在SL端支持EDIT，必须要让DomainService针对该实体类支持开放GUID接口。如下：

[EnableClientAccess()]
public class DomainServiceUser : DomainService
{
    [Query]
    public IList<User> GetUsers()
    {
        return new List<User>()
        {
            new User() { Name = "huzhonghua", Age = 99 }
        };
    }
 
    public User GetAUser()
    {
 
        return new User() { Name = "luminji", Age = 98 };
    }
 
    [Delete]
    public void DeleteUser(User user)
    {
        throw new NotImplementedException();
    }
 
    [Insert]
    public void InsertUser(User user)
    {
        throw new NotImplementedException();
    }
 
    [Update]
    public void UpdateUser(User user)
    {
        throw new NotImplementedException();
    }
 
}