xamarin form: Can the control bind itself? - mvvm

Question

Let say I have an Image tag inside the xaml and wanted to be in square size.
<Grid HorizontalOptions="Fill">
<Grid.RowDefinitions>
<RowDefinition Height="auto">
</RowDefinition>
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*"></ColumnDefinition>
<ColumnDefinition Width="*"></ColumnDefinition>
<ColumnDefinition Width="*"></ColumnDefinition>
<ColumnDefinition Width="*"></ColumnDefinition>
</Grid.ColumnDefinitions>
<Image></Image>
<Image></Image>
<Image></Image>
<Image></Image>
</Grid>
A demo code here have 4 image putting them horizontally within the Grid. The width will be equally defined. So I want the height to be the same as the width. Can I bind themselves like this
<Image x:Name="img" BindingContext="{x:Reference img}" WidthRequest="{Binding HeightRequest}" Grid.Column="1" Grid.Row="0">

Answer 1

Unless you specifically set it somewhere else in code, your WidthRequest will be -1, indicating the control does not explicitly state what width it would like to have, but instead relies on the layout system to workout the correct dimensions.
So this binding, while technically correct, will be useless.
You can try binding to the Width property, which is the readonly property which gets updated with the actual dimensions once the control is laid out.
You can also override the appropriate event and assign the required height there.
Keep in mind that a grid row with height="Auto" will cause A LOT of layout calculation to be done. Especially when changing control sizes after they are already in the visual tree.
Your layout runs **will be* slow.
I suggest you work out a better solution. Such as applying a fixed height to the grid row once the layout engine works out what the cell width for that device is.