Same width of tabitems

Question

I looked for this and found answers, but none is working for me. I have tab control and two items in it. I want Item1 to have same width as Item2. I am using SharedSizeGroup, but only after I select Item2 the width is set to Item1. Can someone help me? Code behind is not an option for me.

<Window x:Class="tabitem_sharedsize.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="MainWindow" SizeToContent="WidthAndHeight">
<Grid>

    <TabControl TabStripPlacement="Top" Grid.IsSharedSizeScope="True" >

        <TabItem Header="Item1">
            <Grid >
                <Grid.ColumnDefinitions>
                    <ColumnDefinition SharedSizeGroup="col_group"/>
                </Grid.ColumnDefinitions>

                <!-- Object Descritions -->
                <GroupBox Margin="5,5,5,5" Grid.Column="0">
                    <GroupBox.Header>
                        Object description
                    </GroupBox.Header>

                    <Grid>
                        <Grid.ColumnDefinitions>
                            <ColumnDefinition Width="150" />
                            <ColumnDefinition Width="250" />
                        </Grid.ColumnDefinitions>

                        <!-- Name -->
                        <Label Grid.Column="0" Grid.Row="0" Content="Name:" />
                        <TextBox  Grid.Column="1" Grid.Row="0" />

                        </Grid>
                </GroupBox>
            </Grid>
        </TabItem>

        <TabItem Header="Item2">
            <Grid>
                <Grid.ColumnDefinitions>
                    <ColumnDefinition SharedSizeGroup="col_group"/>
                </Grid.ColumnDefinitions>

                <Grid Grid.Column="0">
                    <Grid.ColumnDefinitions>
                        <ColumnDefinition Width="*" />
                    </Grid.ColumnDefinitions>

                    <!-- Inputs -->
                    <GroupBox Grid.Column="0" Margin="5,5,5,5">
                        <GroupBox.Header>
                            Inputs
                        </GroupBox.Header>

                        <Grid>

                            <ListView Grid.Row="1" Margin="10,0,0,5">
                                <ListView.View>
                                    <GridView >
                                        <GridViewColumn Header="A" Width="250"/>
                                        <GridViewColumn Header="B" Width="250"/>
                                    </GridView>
                                </ListView.View>
                            </ListView>
                        </Grid>
                    </GroupBox>
                </Grid>
            </Grid>
        </TabItem>
    </TabControl>
</Grid>

Answer 1

You want to simply set the size of first tab same as size of second tab.

<TabItem Header="Item1">
                <Grid >
                    <Grid.ColumnDefinitions>
                        <ColumnDefinition SharedSizeGroup="col_group" Width="400"/>
                    </Grid.ColumnDefinitions>
                 </Grid>
            </TabItem>

In second tab you set the width of 2 columns as 150 and 250.

since there are two columns in second tab but in first tab only one then we set its width to 400.