WPF 数据绑定

1.1绑定到对象

1.1.1、前台绑定

前台代码

   5:  </Grid>

   1:  <Grid x:Name=”GridProductDetails”>

   2:   

   3:  <TextBox Grid.Column="1"  x:Name="txtModelNum" Text="{ Binding Path=ModelNumber}"/>

   4:   

对应后台代码

   1:  Model_Product BP = new BLL_Product().GetProduct(123);

   2:  GridProductDetails.DataContext = BP;

1.1.2、后台绑定

前台代码

   1:  <Grid x:Name=”GridProductDetails”>

   2:       <TextBox Grid.Column="1"  x:Name="txtModelNum" />

   3:  </Grid>

对应后台代码

   1:  Binding B = new Binding(); 

   2:  B.Source=BP; 

   3:  B.Path = new PropertyPath("ModelNumber"); 

   4:  txtModelNum.SetBinding(TextBox.TextProperty, B);

1.2 绑定到控件

有一列表框控件ListBox绑定到一个List<Product> 数据源，显示项为Product对象的ModelName属性，前台代码如下

   1:  <ListBox Name="lstProducts" Margin="5" DisplayMemberPath="ModelName"

   2:                SelectionChanged="lstProducts_SelectionChanged">                

   3:  </ListBox>

对应后台代码为

   1:  private ICollection<Product> products;

   2:  products = App.StoreDb.GetProducts();

   3:  lstProducts.ItemsSource = products;

现在将一个Grid里面的一系列控件绑定到ListBox所选择的数据项上，用于构建“主--详细信息”的显示结构，代码如下

   1:  <Grid DataContext="{Binding ElementName=lstProducts, Path=SelectedItem}" TextBox.TextChanged="txt_TextChanged">

   2:  <TextBox Margin="5"  Text="{Binding Path=ModelNumber}"></TextBox>

   3:  </Grid>

1.3 绑定的双向更新

1.3.1 对象和控件的双向更新

双向更新：即修改对象的属性值后，对应的前台控件自动更新为修改后的值。

前台无需做任何修改，只需在对象类Model定义的时候实现INotifyPropertyChanged接口即可：

   1:  public class Model_Product : INotifyPropertyChanged

   2:    {

   3:        string modelNumber;

   4:   

   5:        public string ModelNumber

   6:        {

   7:            get { return modelNumber; }

   8:            set

   9:            {

  10:                modelNumber = value;

  11:                OnPropertyChanged(new PropertyChangedEventArgs("ModelNumber"));

  12:            }

  13:        }

  14:   

  15:        int _ID;

  16:        public int ID

  17:        {

  18:            get { return _ID; }

  19:            set { _ID = value; }

  20:        }

  21:        /// <summary>

  22:        /// 实现INotifyPropertyChanged接口 可以实现控件值和对象属性值的自动绑定 当修改对象值后 控件的值自动刷新

  23:        /// </summary>

  24:        public event PropertyChangedEventHandler PropertyChanged;

  25:        public void OnPropertyChanged(PropertyChangedEventArgs e)

  26:        {

  27:            if (PropertyChanged != null)

  28:                PropertyChanged(this, e);

  29:        }

  30:    }

  31:   

1.3.2 绑定到对象集合(类似于List<T>)的双向更新

双向更新：即修改对象的属性值后，对应的前台控件自动更新为修改后的值

。

无需些多少代码，只需把数据集合申明为实现了INotifyPropertyChanged接口的集合类型就可以了，在WPF中这个常用的有ObservableCollection<T>这个泛型集合类，如果是WindosForm编程，有个BindingList集合(实现了IBingdingList接口)

   1:  public ICollection<Product> GetProducts()

   2:  {

   3:      DataSet ds = StoreDbDataSet.ReadDataSet();

   4:   

   5:      ObservableCollection<Product> products = new ObservableCollection<Product>();

   6:      foreach (DataRow productRow in ds.Tables["Products"].Rows)

   7:      {

   8:          products.Add(new Product((string)productRow["ModelNumber"],

   9:              (string)productRow["ModelName"], (decimal)productRow["UnitCost"],

  10:              (string)productRow["Description"], (int)productRow["CategoryID"],

  11:              (string)productRow["CategoryName"], (string)productRow["ProductImage"]));

  12:      }

  13:      return products;

  14:  }

1.4 绑定到ADO.NET数据集 DataSet

Controls.ItemsSource=DateSetObject.Tables[n].DefaultView;

需要注明Controls的DisplayMemberPath属性

删除数据集行建议采取的方法

((DataRowView)lstProducts.SelectedItem).Row.Delete();

1.5 绑定到LINQ集合

   1:  public ICollection<Product> GetProductsFilteredWithLinq(decimal minimumCost)

   2:  {

   3:      // Get the full list of products.

   4:      ICollection<Product> products = GetProducts();

   5:   

   6:      // Create a second collection with matching products.

   7:      IEnumerable<Product> matches = from product in products

   8:                                      where product.UnitCost >= minimumCost

   9:                                      select product;

  10:   

  11:      return new ObservableCollection<Product>(matches.ToList());

  12:  }

此处采用public ObservableCollection(List<T> list)实现对LINQ结果集的转换以实现双向更新：即修改对象的属性值后，对应的前台控件自动更新为修改后的值。

1.6 绑定验证

前台代码：

   1:  <Window x:Class="WPFGameTest.DataBinding.TestOfValidationRules"

   2:          xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"

   3:          xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"

   4:          Title="TestOfValidationRules" Height="300" Width="300">

   5:      <StackPanel >

   6:          

   7:          <TextBox x:Name="textBox1" Margin="5" />

   8:          

   9:          <Slider x:Name="slider1" Minimum="-10" Maximum="110" Margin="5" />

  10:                  

  11:   

  12:      </StackPanel>

  13:   

  14:  </Window>

后台代码

   1:  using System;

   2:  using System.Collections.Generic;

   3:  using System.Linq;

   4:  using System.Text;

   5:  using System.Threading.Tasks;

   6:  using System.Windows;

   7:  using System.Windows.Controls;

   8:  using System.Windows.Data;

   9:  using System.Windows.Documents;

  10:  using System.Windows.Input;

  11:  using System.Windows.Media;

  12:  using System.Windows.Media.Imaging;

  13:  using System.Windows.Shapes;

  14:   

  15:  namespace WPFGameTest.DataBinding

  16:  {

  17:      /// <summary>

  18:      /// TestOfValidationRules.xaml 的交互逻辑

  19:      /// </summary>

  20:      public partial class TestOfValidationRules : Window

  21:      {

  22:          public TestOfValidationRules()

  23:          {

  24:               InitializeComponent();  

  25:   

  26:            Binding binding = new Binding("Value")  

  27:            {  

  28:                 Source = this.slider1  

  29:            };  

  30:   

  31:            binding.UpdateSourceTrigger = UpdateSourceTrigger.PropertyChanged;  

  32:              

  33:            RangeValidateRule rvr = new RangeValidateRule();  

  34:            rvr.ValidatesOnTargetUpdated = true;  

  35:            binding.ValidationRules.Add(rvr);  

  36:   

  37:            binding.NotifyOnValidationError = true;  

  38:            this.textBox1.SetBinding(TextBox.TextProperty, binding);  

  39:  

this.textBox1.AddHandler(Validation.ErrorEvent,new RoutedEventHandler(this.ValidationError));

  40:   

  41:          }

  42:          void ValidationError(object sender, RoutedEventArgs e)  

  43:         {

  44:             Control C = sender as Control;

  45:   

  46:             if (Validation.GetErrors(C).Count > 0)

  47:             {

  48:                 (C).Background = new SolidColorBrush(Colors.Red);

  49:                 C.ToolTip = Validation.GetErrors(C)[0].ErrorContent.ToString();

  50:             }

  51:             else

  52:             {

  53:                 (C).Background = new SolidColorBrush(Colors.White);

  54:                 C.ToolTip = null;

  55:             }

  56:   

  57:         }  

  58:   

  59:      }

  60:      public class RangeValidateRule:ValidationRule  

  61:     {  

  62:         public override ValidationResult Validate(object value, System.Globalization.CultureInfo cultureInfo)  

  63:         {  

  64:             double d = 0;  

  65:             if (double.TryParse(value.ToString(),out d))  

  66:             {  

  67:                 if(d >= 0 && d <= 100)  

  68:                 {  

  69:                     return new ValidationResult(true,null);  

  70:                 }  

  71:             }  

  72:   

  73:             return new ValidationResult(false,"Validation Failed !!!");  

  74:         }  

  75:     }  

  76:   

  77:  }

要点在第39行，为一个附加事件，关于附加事件可以参考http://msdn.microsoft.com/zh-cn/library/ms598899(v=VS.95).aspx

另外还有个衍生知识要点是“扩展方法”，这两个应该属于高级一点的编程特性，扩展方法请参照http://msdn.microsoft.com/zh-cn/library/vstudio/bb383977.aspx

1.6.1 注意e.Action == ValidationErrorEventAction.Removed

注意：在值一改变就验证的模式中，不可以用下面的代码方式来处理验证信息。因为当发生一个验证错误时，此时的xe.Action 值为 ValidationErrorEventAction.Added， 代码执行到第10行后跳出ValidationError方法。

此时系统会认为错误验证已经被处理，就会自动再次执行ValidationError，而此时的xe.Action 值为 ValidationErrorEventAction.Removed。

所以使用此方法用于验证，会出现看不到红色背景的效果。

MSDN是这样解释的：

如果发生验证错误，绑定引擎将引发 BindingValidationError 事件。 ValidationError  传递到包含一个新 Exception 的事件处理程序，且 Action 值为 Added。

如果该验证错误得到解决（极有可能是用户通过使用验证信息对项进行更新来解决的），则相同的 ValidationError 将传递到包含原始异常的事件处理程序，且 Action 值为 Removed。

http://msdn.microsoft.com/zh-cn/library/system.windows.controls.validationerroreventaction(v=vs.95).aspx

次验证方法适合于有提交按钮的情况，当点击提交按钮后执行下面的验证。

   1:  void ValidationError(object sender, RoutedEventArgs e)

   2:          {

   3:              Control C = sender as Control;

   4:              ValidationErrorEventArgs xe = e as ValidationErrorEventArgs;

   5:              if (xe.Action == ValidationErrorEventAction.Added )

   6:              {

   7:                  if (Validation.GetErrors(C).Count > 0)

   8:                  {

   9:                      (C).Background = new SolidColorBrush(Colors.Red);

  10:                      C.ToolTip = Validation.GetErrors(C)[0].ErrorContent.ToString();

  11:                  }

  12:              }

  13:              if (xe.Action == ValidationErrorEventAction.Removed)

  14:              {

  15:                  (C).Background = new SolidColorBrush(Colors.White);

  16:              }

  17:   

  18:          }

1.6.2 使用绑定组来验证

   1:  GridProductDetails.DataContext = BP;

   2:  BindingGroup bin = new System.Windows.Data.BindingGroup();

   3:  bin.Name = "bb";

   4:  GridProductDetails.BindingGroup = bin;

   5:  GridProductDetails.BindingGroup.BeginEdit();

   6:   

   7:   

   8:  PositivePriceRule rule = new PositivePriceRule();

   9:  rule.Max = 300;

  10:   

  11:   

  12:  Binding B = new Binding();

  13:  B.Source = BP;

  14:  B.Path = new PropertyPath("ID");//

  15:  B.NotifyOnValidationError = true;

  16:  B.ValidatesOnExceptions = true;

  17:  B.Mode = BindingMode.TwoWay;

  18:  B.UpdateSourceTrigger = UpdateSourceTrigger.PropertyChanged;

  19:  B.ValidationRules.Add(rule);

  20:  

B.BindingGroupName = bin.Name;

  21:   

  22:  txtModelNum.AddHandler(Validation.ErrorEvent, new RoutedEventHandler(this.ValidationError));

  23:  txtModelNum.SetBinding(TextBox.TextProperty, B);

关键的代码在第20行，通过指定Binding对象的BindingGroupName 属性来关联Binding对象到BindingGroup组里面。

此番修改以后，如果出现错误，使用BindingGroup的控件(第4行GridProductDetails.BindingGroup = bin)的边框就会变为红色。