BindingGroup.Items 屬性

定義

命名空間:

System.Windows.Data

組件:

PresentationFramework.dll

取得 Binding 物件 BindingGroup所使用的來源。

public:
 property System::Collections::IList ^ Items { System::Collections::IList ^ get(); };

public System.Collections.IList Items { get; }

member this.Items : System.Collections.IList

Public ReadOnly Property Items As IList

屬性值

IList

綁定物件 BindingGroup所使用的來源。

範例

以下範例是應用程式的一部分，用來檢查使用者是否將兩個物件的屬性設為相等值。 第一個範例建立了兩個 TextBox 控制項，每個控制項都綁定到不同的來源。 第一個TextBox元素的綁定來源 ，來自DataContextTextBox控制元元素的 StackPanel。 object1 在第二個 TextBox上，綁定來源設為 object2。 範例中也產生了顯示驗證錯誤的 。Label

<StackPanel Name="sp1"
            Margin="5"
            DataContext="{Binding Source={StaticResource object1}}"
            Validation.ValidationAdornerSite="{Binding ElementName=label1}"
            Orientation="Horizontal"
            HorizontalAlignment="Center">

  <StackPanel.BindingGroup>
    <BindingGroup Name="bindingGroup">
      <BindingGroup.ValidationRules>
        <src:BindingGroupValidationRule ValidatesOnTargetUpdated="True" />
      </BindingGroup.ValidationRules>
    </BindingGroup>
  </StackPanel.BindingGroup>

  <TextBlock Text="First string" />

  <TextBox Width="150"
           Text="{Binding Path=PropertyA}" />

  <TextBlock Text="Second string" />

  <TextBox Width="150"
           Text="{Binding Source={StaticResource object2}, 
    Path=PropertyB, BindingGroupName=bindingGroup, 
    TargetNullValue=please enter a string}" />

</StackPanel>

<Label Name="label1"
       Content="{Binding ElementName=sp1, Path=(Validation.Errors)[0].ErrorContent}"
       Margin="5"
       Foreground="Red"
       HorizontalAlignment="Center" />

以下範例展示了前一個範例所使用的 。ValidationRule 在此 Validate 方法中，範例取每個 BindingGroup 來源物件，並檢查物件的性質是否相等。

public class Type1
{
    public string PropertyA { get; set; }

    public Type1()
    {
        PropertyA = "Default Value";
    }
}

public class Type2
{
    public string PropertyB { get; set; }

    public Type2()
    {
    }
}

public class BindingGroupValidationRule : ValidationRule
{
    public override ValidationResult Validate(object value, System.Globalization.CultureInfo cultureInfo)
    {
        BindingGroup bg = value as BindingGroup;

        Type1 object1 = null;
        Type2 object2 = null;

        foreach (object item in bg.Items)
        {
            if (item is Type1)
            {
                object1 = item as Type1;
            }

            if (item is Type2)
            {
                object2 = item as Type2;
            }
        }

        if (object1 == null || object2 == null)
        {
            return new ValidationResult(false, "BindingGroup did not find source object.");
        }

        string string1 = bg.GetValue(object1, "PropertyA") as string;
        string string2 = bg.GetValue(object2, "PropertyB") as string;

        if (string1 != string2)
        {
            return new ValidationResult(false, "The two strings must be identical.");
        }

        return ValidationResult.ValidResult;
    }
}

Public Class Type1
    Public Property PropertyA() As String

    Public Sub New()
        PropertyA = "Default Value"
    End Sub
End Class

Public Class Type2
    Public Property PropertyB() As String

    Public Sub New()
    End Sub
End Class

Public Class BindingGroupValidationRule
    Inherits ValidationRule
    Public Overrides Function Validate(ByVal value As Object, ByVal cultureInfo As System.Globalization.CultureInfo) As ValidationResult
        Dim bg As BindingGroup = TryCast(value, BindingGroup)

        Dim object1 As Type1 = Nothing
        Dim object2 As Type2 = Nothing

        For Each item As Object In bg.Items
            If TypeOf item Is Type1 Then
                object1 = TryCast(item, Type1)
            End If

            If TypeOf item Is Type2 Then
                object2 = TryCast(item, Type2)
            End If
        Next item

        If object1 Is Nothing OrElse object2 Is Nothing Then
            Return New ValidationResult(False, "BindingGroup did not find source object.")
        End If

        Dim string1 As String = TryCast(bg.GetValue(object1, "PropertyA"), String)
        Dim string2 As String = TryCast(bg.GetValue(object2, "PropertyB"), String)

        If string1 <> string2 Then
            Return New ValidationResult(False, "The two strings must be identical.")
        End If

        Return ValidationResult.ValidResult

    End Function

End Class

備註

每個用作來源的物件都會被加入 Items 屬性一次，即使該物件是多個綁定的來源。 通常，在 Items中只有一個項目，即使用 的BindingGroup元素中 的DataContext物件。 然而，A BindingGroup 有可能擁有多個來源。 例如，如果綁定物件共享相同 BindingGroupName 但使用不同的來源物件，則每個作為來源物件的物件都屬於 Items。

如果綁定路徑解析為來源的巢狀屬性，則也可能存在多個物件 Items 。 例如，假設一個 TextBox 控制項的綁定是 的一部分 BindingGroup ，而其 DataContext 是 Customer 個具有屬性 Address的物件。 若 Path 的 是屬性Address.ZipCode，則 Address 被加到屬性ItemsBinding上。