看一下图像...请注意包含文本和按钮的网格是如何溢出到下一列的。它为什么这样做？

的数据

<DataGridTemplateColumn Header="Device" Width="*" SortMemberPath="Name" x:Name="DeviceColumn" >
                    <DataGridTemplateColumn.HeaderTemplate>
                        <DataTemplate>
                            <Grid Width="{Binding ElementName=DeviceColumn, Path=ActualWidth}">
                                <Grid.ColumnDefinitions>
                                    <ColumnDefinition Width="Auto"/>
                                    <ColumnDefinition Width="*"/>
                                    <ColumnDefinition Width="Auto"/>
                                </Grid.ColumnDefinitions>
                                <TextBlock Text="Device" Grid.Column="0" HorizontalAlignment="Left"/>
                                <Button Name="FilterButton" Content="..." Width="30" Background="Transparent" Click="FilterColumn" Grid.Column="2" BorderBrush="Transparent" HorizontalAlignment="Right" />
                            </Grid>
                        </DataTemplate>
                    </DataGridTemplateColumn.HeaderTemplate>```

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