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[英]Unable to cast object of type 'System.Windows.Controls.Grid' to type 'System.Windows.Controls.TabItem'
[英]Unable to cast object of type 'System.Windows.Controls.Grid' to type 'System.Windows.Shapes.Ellipse'?
我正在實現一個拖放wpf應用程序,我創建了3個橢圓,我使用拇指控制將橢圓拖放到地圖中,我希望得到橢圓的放置位置。 但是我拖動橢圓時會出現錯誤,如下所示:
無法將“System.Windows.Controls.Grid”類型的對象強制轉換為“System.Windows.Shapes.Ellipse”類型
我的XAML:
<Window x:Class="DragandDropMFP.MainWindow"
xmlns:local="clr-namespace:DragandDropMFP"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:telerik="http://schemas.telerik.com/2008/xaml/presentation"
Title="MainWindow" Height="350" Width="525">
<Grid x:Name="maingrid" MouseMove="MainGrid_MouseMove">
<Grid.Background>
<ImageBrush ImageSource="/Map/Capture.Png" />
</Grid.Background>
<Canvas>
<Thumb Canvas.Left="38" Canvas.Top="22" DragDelta="Thumb_DragDelta">
<Thumb.Template>
<ControlTemplate>
<Viewbox Width="50" Height="50">
<Grid Width="20" Height="20">
<Ellipse
Fill="Blue"
MouseMove="DragMouseMove"/>
<TextBlock HorizontalAlignment="Center" Text="Printer1" FontSize="4" TextAlignment="Center" VerticalAlignment="Center"/>
</Grid>
</Viewbox>
</ControlTemplate>
</Thumb.Template>
</Thumb>
<Thumb Canvas.Left="37" Canvas.Top="100" DragDelta="Thumb_DragDelta">
<Thumb.Template>
<ControlTemplate>
<Viewbox Width="50" Height="50">
<Grid Width="20" Height="20">
<Ellipse Fill="Yellow"
MouseMove="DragMouseMove"/>
<TextBlock HorizontalAlignment="Center" Text="Printer2" FontSize="4" TextAlignment="Center" VerticalAlignment="Center"/>
</Grid>
</Viewbox>
</ControlTemplate>
</Thumb.Template>
</Thumb>
<Thumb Canvas.Left="37" Canvas.Top="174" DragDelta="Thumb_DragDelta">
<Thumb.Template>
<ControlTemplate>
<Viewbox Width="50" Height="50">
<Grid Width="20" Height="20">
<Ellipse Fill="Red"
MouseMove="DragMouseMove"/>
<TextBlock HorizontalAlignment="Center" Text="Printer3" FontSize="4" TextAlignment="Center" VerticalAlignment="Center"/>
</Grid>
</Viewbox>
</ControlTemplate>
</Thumb.Template>
</Thumb>
</Canvas>
<TextBlock x:Name="ctlStatus" HorizontalAlignment="Stretch" Height="30" TextWrapping="Wrap" Text="status" VerticalAlignment="Bottom" RenderTransformOrigin="0.495,-4.7" />
</Grid>
</Window>
我的xaml.cs:
public MainWindow()
{
InitializeComponent();
}
private void MainGrid_MouseMove(object sender, MouseEventArgs e)
{
Mouse.OverrideCursor = Cursors.Arrow;
objmoveposition(sender, e);
}
private void DragMouseMove(object sender, MouseEventArgs e)
{
Mouse.OverrideCursor = Cursors.Hand;
objmoveposition(sender, e);
}
private void objmoveposition(object sender, MouseEventArgs e)
{
if (e.LeftButton == MouseButtonState.Pressed)
{
if (Mouse.OverrideCursor == Cursors.Hand)
{
Ellipse objTextbox = (Ellipse)sender; <--Error
if (objTextbox != null)
{
//----< Move Control >----
Point mousePoint = e.GetPosition(this);
//< Vertical >
int posY = (int)mousePoint.Y;
int actHeight = (int)Application.Current.MainWindow.Height;
int margin_Bottom = actHeight - (posY + (int)objTextbox.Height + (int)SystemParameters.CaptionHeight + (int)SystemParameters.BorderWidth + 4);
//< Horizontal >
int posX = (int)mousePoint.X;
int actWidth = (int)Application.Current.MainWindow.Width;
int margin_Right = actWidth - (posX + (int)objTextbox.Width + (int)SystemParameters.BorderWidth);
ctlStatus.Text = "Top=" + posY + " margin_bottom=" + margin_Bottom + " WinHeigth=" + actHeight + Environment.NewLine + " Left=" + posX + " margin_Right=" + margin_Right + "WinWidth=" + actWidth;
//ctlStatus.Text = "position=" + objTextbox.ActualHeight;
}
}
}
}
private void Thumb_DragDelta(object sender, System.Windows.Controls.Primitives.DragDeltaEventArgs e)
{
UIElement thumb = e.Source as UIElement;
Canvas.SetLeft(thumb, Canvas.GetLeft(thumb) + e.HorizontalChange);
Canvas.SetTop(thumb, Canvas.GetTop(thumb) + e.VerticalChange);
}
非常感謝您的指導! 謝謝!
sender
是引發事件的橢圓,因此您可以將其替換為:
Ellipse objTextbox = ellipse1;
有了這個;
Ellipse objTextbox = (Ellipse)sender;
只要您只將事件分配給省略號,這是安全的。 如果將其分配給其他對象類型,則需要在轉換之前檢查發送方的類型。
您不需要對象的名稱。
剛剛通過將橢圓更改為網格而發現,一切都像cham ..
Ellipse objTextbox = (Ellipse)sender;
改成
Grid objTextbox = (Grid)sender;
謝謝!
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