如何在WPF中使按钮内的网格具有100％的宽度?

我在窗口上有一个与窗口大小相符的按钮.我在按钮内放了一个网格，其中有一行和两列，在第一列中放置了一个路径，在第二列中放置了一个文本框.

I have a button on a window that sizes to the window. I have put a grid inside the button with one row and two columns, and put a path in first column, and a textbox in the second.

我的问题是我无法使用按钮来拉伸网格.

My problem is I can't get the grid to stretch with the button.

这是正在发生的事情:

这就是我要发生的事情:

Here is what I want to happen:

我有网格Horizo​​ntalAlignment ="Stretch"，但没有拉伸. 我在这里做什么错了?

I have the grids HorizontalAlignment="Stretch", yet it is not stretching. What am I doing wrong here?

这是代码:

    <Window x:Class="GridInButtonIssue.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:GridInButtonIssue"
        mc:Ignorable="d"
        Title="MainWindow" Height="136.5" Width="269.839">
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto" />
        </Grid.RowDefinitions>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="*" />
        </Grid.ColumnDefinitions>
        <Button x:Name="btn_SelectMode" Grid.Row="0" Margin="0,35,0,0" >
            <Grid HorizontalAlignment="Stretch">
                <Grid.RowDefinitions>
                    <RowDefinition Height="20" />
                </Grid.RowDefinitions>
                <Grid.ColumnDefinitions>
                    <ColumnDefinition Width="6*" />
                    <ColumnDefinition Width="4*" />
                </Grid.ColumnDefinitions>
                <Canvas x:Name="svg2" Grid.Column="0" Width="25" Height="25" HorizontalAlignment="Center">
                    <Canvas.RenderTransform>
                        <TranslateTransform X="0" Y="0"/>
                    </Canvas.RenderTransform>
                    <Canvas x:Name="layer1">
                        <Canvas.RenderTransform>
                            <TranslateTransform X="-298.50531" Y="-576.33075"/>
                        </Canvas.RenderTransform>
                        <Ellipse xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Canvas.Left="298.6" Canvas.Top="576.4" Width="19.9" Height="19.9" x:Name="path4144" Fill="#FF951718" StrokeThickness="0.14452878" Stroke="#FFFD0000" StrokeMiterLimit="4" StrokeLineJoin="Miter" StrokeStartLineCap="Flat" StrokeEndLineCap="Flat" Opacity="1"/>
                    </Canvas>
                </Canvas>
                <TextBlock Grid.Column="1" Text="Test Button" HorizontalAlignment="Left" />
            </Grid>
        </Button>
    </Grid>
</Window>