本文介紹為silverlight DataGrid增加AutoCompleteBox列的兩種方法，眾所周知DataGrid有個模板列(DataGridTempleteColumn)列,其功能非常強大，在模板列中基本上什么組件都可以放，因此我們不難想到用模板列很容易就可以實現.下面展示模板列的方式的幾個步驟：

　　1.在Resource中定義AutoCompleteBox的ItemTemplate,定義下拉列表中的每一項的顯示方式及其內容.

<data:DataGrid.Resources>  

<DataTemplate x:Name="currencyDataTemplate">  

 <TextBlock Text="{Binding Path=Name}"/>  

</DataTemplate>  

</data:DataGrid.Resources>  

　　2.定義AutoCompleteBox的數據源

<data:DataGrid.Resources>
   <riaControls:DomainDataSource x:Key=

"currencyDomainDataSource" AutoLoad="True" 
d:DesignData="{d:DesignInstance models:Currency, CreateList=true}" Height="0" 
   LoadedData= "currencyDomainDataSource_LoadedData" 

Name="currencyDomainDataSource" 
QueryName= "GetCurrenciesQuery" Width="0">
  <riaControls:DomainDataSource.DomainContext>
  <services:MtsDomainContext />
     </riaControls:DomainDataSource.DomainContext>
  </riaControls:DomainDataSource>

      <DataTemplate x:Name="currencyDataTemplate">
         <TextBlock Text="{Binding Path=Name}"/>
      </DataTemplate>
                
  </data:DataGrid.Resources>

　　2.定義DataGridTemplateColumn字段

<data:DataGridTemplateColumn x:Name="currencyColumn" 

Header="Currency" Width="SizeToHeader">  
     <data:DataGridTemplateColumn.CellTemplate>  
         <DataTemplate>  
   <TextBlock Text="{Binding Currency}" VerticalAlignment=

"Center" Margin="3"/>  
         </DataTemplate>  
     </data:DataGridTemplateColumn.CellTemplate>  
     <data:DataGridTemplateColumn.CellEditingTemplate>  
         <DataTemplate>  
             <input:AutoCompleteBox x:Name="currencyAutoComplete" Text="{Binding Path=CurrencyID,Mode=TwoWay}"                                                       
   ItemsSource= "{Binding Path=Data,Source=

{StaticResource currencyDomainDataSource}}"  
   ValueMemberPath= "Name" ItemTemplate=

"{StaticResource currencyDataTemplate}" />    
         </DataTemplate>  
     </data:DataGridTemplateColumn.CellEditingTemplate>  
 </data:DataGridTemplateColumn>  

　　3.如果需要，實現轉換器類，實現IValueConverter接口，binding表達式中指定轉換器

　　在上面例子中數據源的CurrencyID對應Currency的ID字段，用戶輸入時輸入Currency的Name字段，因此需要ID和Name之間進行轉換.

 public class CurrencyValueConverter : IValueConverter
     {

         #region IValueConverter Members
        
          public object Convert(object value, Type targetType, 

object parameter, System.Globalization.CultureInfo culture)
         {
             //這里實現轉換成Name
             return value;            
         }

   public object ConvertBack(object value, Type targetType, 

object parameter, System.Globalization.CultureInfo culture)
         {
             //這里實現從Name轉換成ID
             return value;
         }

          #endregion

　　4.在Resouces中聲明Converter

1. <helper:CurrencyValueConverter x:Key="currencyValueConverter"/>  

　　5.修改binding語句指定Converter及其Convert的參數等信息.

1. Text="{Binding Path=CurrencyID,Mode=TwoWay,Converter={StaticResource currencyValueConverter}}"  

　　經過以上步驟基本完成了AutoCompleteBox列增加.

　　上述方法有以下問題：

　　1.步驟比較多

　　2.為每個使用到AutoCompleteBox列的地方都要以上處理，重復工作較多

　　3.為每個類似Key，Value的轉換都要寫個Converter類

　　那么我們能否寫個類似DataGridTextColumn的DataGridAutoCompleteColumn類，通過簡單的綁定就可以完成以上工作呢？答案肯定是可以的.

　　下面讓我們來動手實現這個DataGridAutoCompleteColumn吧！

　　設計DataGridAutoCompleteColumn類面臨幾個問題：

　　1.為我們的DataGridAutoCompleteColumn選擇一個合適的基類,并重寫相應的方法

　　2.實現一個通用的轉換器，完成Key,Value的映射

　　解決方法：

　　對于第一個問題我們選擇DataGridBoundColumn類做為基類，重寫GenerateElement，GenerateEditingElement，CancelCellEdit，PrepareCellForEdit等方法.

　　對于第二個問題我們指定ValueMemberPath,DisplayMemberPath，利用反射機制來實現這兩個字段間的映射即可。下面是我實現的代碼：

DataGridAutoCompleteColumn實現代碼：

public class DataGridAutoCompleteColumn : DataGridBoundColumn
     {
   public DataGridAutoCompleteColumn()
         {
     //this.DefaultStyleKey = typeof(DataGridAutoCompleteColumn);  
  //this._converter = new DataGridAutoCompleteColumnConverter(this);  
            
         }

   public override System.Windows.Data.Binding Binding
         {
             get
             {
                 return base.Binding;
             }
             set
             {
                 if (value != null)
                 {
  if (value.Converter == null)//如果沒指定轉換器，指定通用轉換器來轉
                     {
     value.Converter = new DataGridAutoCompleteColumnConverter();
                     }                    
                 }

                 base.Binding = value;
             }
         }

         private IValueConverter Converter
         {
             get 
             {
                 if (this.Binding != null)
                 {
                     return this.Binding.Converter;
                 }
                 return null;
             }
             //set { this._converter = value; }
         }

   protected override FrameworkElement GenerateElement

(DataGridCell cell, object dataItem)
         {
             //throw new NotImplementedException();
            
             TextBlock block = new TextBlock();
             block.Margin = new Thickness(4.0);
             block.VerticalAlignment = VerticalAlignment.Center;
            
             if ((this.Binding != null) || !DesignerProperties.IsInDesignTool)
             {
    block.SetBinding(TextBlock.TextProperty, this.Binding);
             }
             return block;

         }

   protected override FrameworkElement GenerateEditingElement

(DataGridCell cell, object dataItem)
         {
             AutoCompleteBox box = new AutoCompleteBox();
             box.VerticalAlignment = VerticalAlignment.Center;

   box.Background = new SolidColorBrush(Colors.Transparent);


  if ((this.Binding != null) || !DesignerProperties.IsInDesignTool)
             {
                 box.ItemsSource = this.ItemsSource;
   DataTemplate itemTemplate = this.ItemTemplate;
   if (itemTemplate == null  && !String.IsNullOrEmpty(this.DisplayMemberPath))
                 {
   string xaml =  "<DataTemplate xmlns=

\"//schemas.microsoft.com/winfx/2006/xaml/presentation\"> 
<TextBlock Text=\"{Binding Path=" +
      this.DisplayMemberPath +  "}\" /> </DataTemplate>";
    itemTemplate = (DataTemplate)XamlReader.Load(xaml);
                 }

                 box.ItemTemplate = itemTemplate;
                
                 if (!String.IsNullOrEmpty(DisplayMemberPath))
                 {
                     Binding valueBinding = new Binding(this.DisplayMemberPath);                   
                     box.ValueMemberBinding = valueBinding;
                 }
                 else if (!String.IsNullOrEmpty(ValueMemberPath))
                 {
   box.ValueMemberPath = this.ValueMemberPath;
                 }

     box.SetBinding(AutoCompleteBox.TextProperty, this.Binding);
                 //box.SetBinding(base.BindingTarget, this.Binding);
             }

             return box;            
         }

   protected override void CancelCellEdit

(FrameworkElement editingElement, object uneditedValue)
         {
             //base.CancelCellEdit(editingElement, uneditedValue);
             AutoCompleteBox box = editingElement as AutoCompleteBox;
             if (box != null)
             {
                 if (this.RequiredConverter)
                 {
                      box.Text = (string)this.Converter.Convert(uneditedValue, typeof(string), 

null, System.Globalization.CultureInfo.CurrentCulture);
  }
                 else if(uneditedValue != null)
   {
    box.Text = uneditedValue.ToString();
                 }
             }
         }

   protected override object PrepareCellForEdit

(FrameworkElement editingElement, RoutedEventArgs editingEventArgs)
         {
   AutoCompleteBox box = editingElement as AutoCompleteBox;
             if (box != null)
             {
                 return box.Text;               
             }
             else
             {                
                 return string.Empty;
             }
   //return base.PrepareCellForEdit(editingElement, editingEventArgs);
         }

         private bool RequiredConverter
         {
             get
             {
                 return !String.IsNullOrEmpty(this.ValueMemberPath)
                     && !String.IsNullOrEmpty(this.DisplayMemberPath);
             }
         }               

         #region AutoComplete

         public string ValueMemberPath
         {
             get { return GetValue(ValueMemberPathProperty) as string; }
             set { SetValue(ValueMemberPathProperty, value); }
         }

          // Using a DependencyProperty as the backing store for ValueMemberPath.  

This enables animation, styling, binding, etc...
  public static readonly DependencyProperty ValueMemberPathProperty =
              DependencyProperty.Register( "ValueMemberPath", typeof(string), typeof(DataGridAutoCompleteColumn), 

new PropertyMetadata(null, OnMemberPathPropertyChanged));


         public string DisplayMemberPath
         {
             get { return GetValue(DisplayMemberPathProperty) as string; }
             set { SetValue(DisplayMemberPathProperty, value); }
         }

          // Using a DependencyProperty as the backing store for DisplayMemberPath. 

 This enables animation, styling, binding, etc...
         public static readonly DependencyProperty DisplayMemberPathProperty =
              DependencyProperty.Register( "DisplayMemberPath", typeof(string), typeof(DataGridAutoCompleteColumn), 

new PropertyMetadata(null, OnMemberPathPropertyChanged));

        
         public IEnumerable ItemsSource
         {
             get { return GetValue(ItemsSourceProperty) as IEnumerable; }
             set { SetValue(ItemsSourceProperty, value); }
         }

          // Using a DependencyProperty as the backing store for ItemsSource.  

This enables animation, styling, binding, etc...
         public static readonly DependencyProperty ItemsSourceProperty =
             DependencyProperty.Register( "ItemsSource", typeof(IEnumerable),
   typeof(DataGridAutoCompleteColumn), new PropertyMetadata

(null, OnItemsSourcePropertyChanged));


         public DataTemplate ItemTemplate
         {
             get { return GetValue(ItemTemplateProperty) as DataTemplate; }
             set { SetValue(ItemTemplateProperty, value); }
         }

          // Using a DependencyProperty as the backing store for ItemTemplate.  

This enables animation, styling, binding, etc...
         public static readonly DependencyProperty ItemTemplateProperty =
              DependencyProperty.Register( "ItemTemplate", typeof(DataTemplate), typeof(DataGridAutoCompleteColumn),

 new PropertyMetadata(null));

          private static void OnMemberPathPropertyChanged(DependencyObject d, 

DependencyPropertyChangedEventArgs e)
         {
  DataGridAutoCompleteColumn control = d as DataGridAutoCompleteColumn;
             if (control != null)
             {
                 control.OnMemberPathChanged();
             }
         }

        
         private void OnMemberPathChanged()
         {
             //set binding converter
              DataGridAutoCompleteColumnConverter converter =

 this.Converter as DataGridAutoCompleteColumnConverter;
             if (converter != null)
             {
                 converter.ValueMember = this.ValueMemberPath;
                 converter.DisplayMember = this.DisplayMemberPath;   
             }
         }

          private static void OnItemsSourcePropertyChanged

(DependencyObject d, DependencyPropertyChangedEventArgs e)
         {
   DataGridAutoCompleteColumn control = d as DataGridAutoCompleteColumn;
             if (control != null)
             {
                 control.OnItemsSourceChanged();
             }
         }

         private void OnItemsSourceChanged()
         {
             IValueConverter converter = this.Converter;//this._converter as DataGridAutoCompleteColumnConverter;
  if (converter != null  && converter is DataGridAutoCompleteColumnConverter)
             {
   ((DataGridAutoCompleteColumnConverter)converter).ItemsSource = 

this.ItemsSource;
             }
         }

         #endregion                     
     }

DataGridAutoCompleteColumnConverter類實現代碼：

   class DataGridAutoCompleteColumnConverter : IValueConverter
     {
         private IEnumerable _itemsSource;
         private PropertyInfo _valuePropertyInfo;
         private PropertyInfo _displayPropertyInfo;
         private Type _elementType;
         private bool _initialized = false;

         public string DisplayMember { get; set; }

         public string ValueMember { get; set; }

         public IEnumerable ItemsSource
         {
             get { return this._itemsSource; }
             set
             {
                 this._itemsSource = value;
                 _initialized = false;
             }
         }

         private void Init()
         {
             if (_initialized) return;

    if (this.ItemsSource != null  && !String.IsNullOrEmpty(this.DisplayMember)
  && !String.IsNullOrEmpty(this.ValueMember))
             {
    IEnumerator enumrator = this.ItemsSource.GetEnumerator();
  enumrator.MoveNext();
                 object current = enumrator.Current;
                 Type type = current.GetType();
                 if (current != null)
     if (!String.IsNullOrEmpty(this.ValueMember))
     {
                         _valuePropertyInfo = type.GetProperty(this.ValueMember);
                     }
                     if (!String.IsNullOrEmpty(this.DisplayMember))
                     {
                         _displayPropertyInfo = type.GetProperty(this.DisplayMember);
                     }
                     _elementType = type;
                     _initialized = true;
                 }
                
             }
             else
             {
   this._valuePropertyInfo = null;
                 this._displayPropertyInfo = null;
             }
         }

     #region IValueConverter Members

          public object Convert(object value, Type targetType, object parameter,

 System.Globalization.CultureInfo culture)
         {
      if (String.IsNullOrEmpty(this.DisplayMember) 

&& String.IsNullOrEmpty(this.ValueMember))
                 return value;
             this.Init();

             if (this._displayPropertyInfo == null) return value;

             if (targetType == this._displayPropertyInfo.PropertyType)
             {
                 if (ItemsSource == null)
                     return value;

                 if (value.GetType() == this._elementType)
                 {
                     return this._displayPropertyInfo.GetValue(value, null);
                 }

                 object item = null;
                 foreach (object o in this.ItemsSource)
                 {
                     if (value.Equals(this._valuePropertyInfo.GetValue(o, null)))
                     {
                         item = o;
                         break;
                     }
                 }

                 if (item != null)
                 {
                     return this._displayPropertyInfo.GetValue(item, null);
                 }
             }
             return value;
         }

   public object ConvertBack(object value, Type targetType, object parameter, 

System.Globalization.CultureInfo culture)
         {
             this.Init();

             if(value == null)return value;

             if (this._displayPropertyInfo != null)
             {
                 object item = null;
                 foreach (object o in this.ItemsSource)
                 {
  if (value.Equals(this._displayPropertyInfo.GetValue(o, null)))
                     {
                         item = o;
                         break;
                     }
                 }

   if (item != null  && this._valuePropertyInfo != null)
                 {
                     return this._valuePropertyInfo.GetValue(item, null);
                 }
                 return item;
             }
   else if(this._valuePropertyInfo != null  && value.GetType() == this._elementType)           
             {
    return this._valuePropertyInfo.GetValue(value, null);
             }
             else
             {
                 if ((targetType != null)  && targetType.IsClass)
                 {
                     string str = value as string;
                     if (str == string.Empty)
                     {
                         return null;
                     }
                 }
                 return value;
             }
         }

         #endregion
     }

　　到此我們的DataGridAutoCompleteColumn類基本開發完成.

　　使用時我們只需要以下聲明就可以：

<local:DataGridAutoCompleteColumn x:Name="currencyColumn"   
     Binding="{Binding Path=CurrencyID}"   
    ItemsSource= "{Binding Source=

{StaticResource currencyDomainDataSource},Path=Data}"   
   ValueMemberPath= "ID" DisplayMemberPath="Name"

Header="Name" Width="SizeToHeader"/>

　　當然在Resource里面還是要定義ItemsSource的數據源的。