DataGrid选择所有按钮加载缓慢

Question

我有一个带有ItemsSource的DataGrid和带有绑定值的列。 出于某种原因，“全选按钮”最后加载，因此首先列标题向左对齐，并且在加载整个内容之后，出现“全选按钮”。我该如何修复那个眨眼？ http://i.stack.imgur.com/EhesT.png

这是我的代码     

                <DataGrid.RowHeaderTemplate>
                    <DataTemplate>
                        <TextBlock Text="{Binding RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type DataGridRow}}, 
                            Path=Item.RowHeader}"
                                   HorizontalAlignment="Stretch"
                                   MinWidth="55"/>
                    </DataTemplate>
                </DataGrid.RowHeaderTemplate>

                <DataGrid.Columns>
                    <!--m-->
                    <DataGridTextColumn Binding="{Binding Path=m, IsAsync=True, StringFormat='{}{0:0.##}'}" Header="m"/>

                    <!--α-->
                    <DataGridTextColumn Binding="{Binding Path=a, IsAsync=True}" Header="α" />

                    <!--h-->
                    <DataGridTextColumn Binding="{Binding Path=h, IsAsync=True, StringFormat='{}{0:0.#}'}" Header="h" />

                    <!--D1-->
                    <DataGridTextColumn Binding="{Binding Path=D1, IsAsync=True, StringFormat='{}{0:F0}'}">
                        <DataGridTextColumn.Header>
                            <StackPanel Orientation="Horizontal">
                                <TextBlock>
                                    D
                                    <InlineUIContainer BaselineAlignment="Subscript">
                                        <TextBlock Text="1"/> 
                                    </InlineUIContainer>
                                </TextBlock>
                            </StackPanel>
                        </DataGridTextColumn.Header>
                    </DataGridTextColumn>

                    <!--D2-->
                    <DataGridTextColumn Binding="{Binding Path=D2, IsAsync=True, StringFormat='{}{0:F0}'}">
                        <DataGridTextColumn.Header>
                            <StackPanel Orientation="Horizontal">
                                <TextBlock>
                                    D
                                    <InlineUIContainer BaselineAlignment="Subscript">
                                        <TextBlock Text="2"/> 
                                    </InlineUIContainer>
                                </TextBlock>
                            </StackPanel>
                        </DataGridTextColumn.Header>
                    </DataGridTextColumn>

                </DataGrid.Columns>

            </DataGrid>