HOW TO：設定項目的高度屬性
更新：2007 年 11 月
範例
本範例會以視覺化方式顯示 Windows Presentation Foundation (WPF) 四個與高度相關的屬性在呈現行為方面的差異。
FrameworkElement 類別會公開四個屬性，描述項目的高度特性。這四個屬性可能會衝突，因此若發生衝突，優先採用的值會決定如下：MinHeight 值優先於 MaxHeight 值，而後者又優先於 Height 值。第四個屬性 ActualHeight 是唯讀的。
下列可延伸標記語言 (XAML) 範例會將 Rectangle 項目 (rect1) 繪製為 Canvas 的子項。您可以使用一系列的清單方塊表示 MinHeight、MaxHeight 和 Height 的屬性值，以變更 Rectangle 的高度屬性。利用這種方式，每個屬性的優先順序就能以視覺化方式顯示。
<Canvas Height="200" MinWidth="200" Background="#b0c4de" VerticalAlignment="Top" HorizontalAlignment="Center" Name="myCanvas" Margin="0,0,0,50">
<Rectangle HorizontalAlignment="Center" Canvas.Top="50" Canvas.Left="50" Name="rect1" Fill="#4682b4" Height="100" Width="100"/>
</Canvas>
...
<TextBlock Grid.Row="1" Grid.Column="0" Margin="10,0,0,0" TextWrapping="Wrap">Set the Rectangle Height:</TextBlock>
<ListBox Grid.Column="1" Grid.Row="1" Margin="10,0,0,0" Height="50" Width="50" SelectionChanged="changeHeight">
<ListBoxItem>25</ListBoxItem>
<ListBoxItem>50</ListBoxItem>
<ListBoxItem>75</ListBoxItem>
<ListBoxItem>100</ListBoxItem>
<ListBoxItem>125</ListBoxItem>
<ListBoxItem>150</ListBoxItem>
<ListBoxItem>175</ListBoxItem>
<ListBoxItem>200</ListBoxItem>
</ListBox>
<TextBlock Grid.Row="1" Grid.Column="2" Margin="10,0,0,0" TextWrapping="Wrap">Set the Rectangle MinHeight:</TextBlock>
<ListBox Grid.Column="3" Grid.Row="1" Margin="10,0,0,0" Height="50" Width="50" SelectionChanged="changeMinHeight">
<ListBoxItem>25</ListBoxItem>
<ListBoxItem>50</ListBoxItem>
<ListBoxItem>75</ListBoxItem>
<ListBoxItem>100</ListBoxItem>
<ListBoxItem>125</ListBoxItem>
<ListBoxItem>150</ListBoxItem>
<ListBoxItem>175</ListBoxItem>
<ListBoxItem>200</ListBoxItem>
</ListBox>
<TextBlock Grid.Row="1" Grid.Column="4" Margin="10,0,0,0" TextWrapping="Wrap">Set the Rectangle MaxHeight:</TextBlock>
<ListBox Grid.Column="5" Grid.Row="1" Margin="10,0,0,0" Height="50" Width="50" SelectionChanged="changeMaxHeight">
<ListBoxItem>25</ListBoxItem>
<ListBoxItem>50</ListBoxItem>
<ListBoxItem>75</ListBoxItem>
<ListBoxItem>100</ListBoxItem>
<ListBoxItem>125</ListBoxItem>
<ListBoxItem>150</ListBoxItem>
<ListBoxItem>175</ListBoxItem>
<ListBoxItem>200</ListBoxItem>
</ListBox>
下列程式碼後置範例會處理 SelectionChanged 事件所引發的事件。每個自訂方法會採用 ListBox 的輸入、將值剖析為 Double，然後將值套用到指定的高度相關屬性。高度值也會轉換成字串，並寫入名為 txt1 的 TextBlock 項目。
Private Sub changeHeight(ByVal sender As Object, ByVal args As SelectionChangedEventArgs)
Dim li As ListBoxItem = CType(CType(sender, ListBox).SelectedItem, ListBoxItem)
Dim sz1 As Double = Double.Parse(li.Content.ToString())
rect1.Height = sz1
rect1.UpdateLayout()
txt1.Text = "ActualHeight is set to " + rect1.ActualHeight.ToString
txt2.Text = "Height is set to " + rect1.Height.ToString
txt3.Text = "MinHeight is set to " + rect1.MinHeight.ToString
txt4.Text = "MaxHeight is set to " + rect1.MaxHeight.ToString
End Sub
Private Sub changeMinHeight(ByVal sender As Object, ByVal args As SelectionChangedEventArgs)
Dim li As ListBoxItem = CType(CType(sender, ListBox).SelectedItem, ListBoxItem)
Dim sz1 As Double = Double.Parse(li.Content.ToString())
rect1.MinHeight = sz1
rect1.UpdateLayout()
txt1.Text = "ActualHeight is set to " + rect1.ActualHeight.ToString
txt2.Text = "Height is set to " + rect1.Height.ToString
txt3.Text = "MinHeight is set to " + rect1.MinHeight.ToString
txt4.Text = "MaxHeight is set to " + rect1.MaxHeight.ToString
End Sub
Private Sub changeMaxHeight(ByVal sender As Object, ByVal args As SelectionChangedEventArgs)
Dim li As ListBoxItem = CType(CType(sender, ListBox).SelectedItem, ListBoxItem)
Dim sz1 As Double = Double.Parse(li.Content.ToString())
rect1.MaxHeight = sz1
rect1.UpdateLayout()
txt1.Text = "ActualHeight is set to " + rect1.ActualHeight.ToString
txt2.Text = "Height is set to " + rect1.Height.ToString
txt3.Text = "MinHeight is set to " + rect1.MinHeight.ToString
txt4.Text = "MaxHeight is set to " + rect1.MaxHeight.ToString
End Sub
private void changeHeight(object sender, SelectionChangedEventArgs args)
{
ListBoxItem li = ((sender as ListBox).SelectedItem as ListBoxItem);
Double sz1 = Double.Parse(li.Content.ToString());
rect1.Height = sz1;
rect1.UpdateLayout();
txt1.Text= "ActualHeight is set to " + rect1.ActualHeight;
txt2.Text= "Height is set to " + rect1.Height;
txt3.Text= "MinHeight is set to " + rect1.MinHeight;
txt4.Text= "MaxHeight is set to " + rect1.MaxHeight;
}
private void changeMinHeight(object sender, SelectionChangedEventArgs args)
{
ListBoxItem li = ((sender as ListBox).SelectedItem as ListBoxItem);
Double sz1 = Double.Parse(li.Content.ToString());
rect1.MinHeight = sz1;
rect1.UpdateLayout();
txt1.Text= "ActualHeight is set to " + rect1.ActualHeight;
txt2.Text= "Height is set to " + rect1.Height;
txt3.Text= "MinHeight is set to " + rect1.MinHeight;
txt4.Text= "MaxHeight is set to " + rect1.MaxHeight;
}
private void changeMaxHeight(object sender, SelectionChangedEventArgs args)
{
ListBoxItem li = ((sender as ListBox).SelectedItem as ListBoxItem);
Double sz1 = Double.Parse(li.Content.ToString());
rect1.MaxHeight = sz1;
rect1.UpdateLayout();
txt1.Text= "ActualHeight is set to " + rect1.ActualHeight;
txt2.Text= "Height is set to " + rect1.Height;
txt3.Text= "MinHeight is set to " + rect1.MinHeight;
txt4.Text= "MaxHeight is set to " + rect1.MaxHeight;
}
如需完整範例，請參閱高度屬性範例。