Grid row height TemplateBinding throwing exception

Question

I'm trying to hide a row of a Grid in my ControlTemplate based on the value of a boolean BindableProperty.

<ContentPage.Resources>

...

    <ControlTemplate x:Key="HeaderWithNavigation">
                <Grid x:Name="HeaderWithNavigationGrid">
                    <Grid.RowDefinitions>
                        <RowDefinition Height="0.1*" />
                        <RowDefinition Height="0.8*" />
                        <RowDefinition Height="{TemplateBinding ShowFooter, Converter={StaticResource GridRowVisibilityConverter}}" />
                    </Grid.RowDefinitions>
                </Grid>
     </ControlTemplate>

...

</ContentPage.Resources>

The ShowFooter is defined as such:

public static readonly BindableProperty ShowFooterProperty = BindableProperty.Create(nameof(ShowFooter), typeof(bool), typeof(MyDefaultTemplatePage), default(bool));
        public bool ShowFooter
        {
            get => (bool)GetValue(ShowFooterProperty);
            set => SetValue(ShowFooterProperty, value);
        }

I borrowed the coverter from here. I dont get any compilation errors but when I load the page that uses this template, the app crashes with a System.InvalidOperationException: 'Operation is not valid due to the current state of the object.'

Answer 1

Hello,​

Welcome to our Microsoft Q&A platform!

I tested your code in a basic demo and faced the same issue. It's caused by the limit of TemplateBinding, check this link. To fix this issue, try using Binding instead.

   <ControlTemplate x:Key="_template">  
       <Grid>  
           <Grid.RowDefinitions>  
               <RowDefinition Height="25" />  
               <RowDefinition Height="35" />  
               <RowDefinition Height="{TemplateBinding IsShowing, Converter={StaticResource _converter}}" />  
           </Grid.RowDefinitions>  
           ...  
       </Grid>  
   </ControlTemplate>  

Best Regards,

Jarvan Zhang

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