How to fix Error "XLS0432 The property 'IsEmpty' was not found in type 'String' in WPF

I am making a search box and in the process I get an error in the line

Visibility="{Binding ElementName=txtSearch, Path=Text.IsEmpty, Converter={StaticResource BoolToVis}}"

Specifically under Path=Text.IsEmpty. I am assuming this error happens because the value of the searchBox will be null at times but I have no idea how to get rid of it.

As long as the error appears I can still compile and run the applicaiton for which I am making the search box but the design of the search box is not what I want. It shows the skeleton for the search box I made instead of the style I made for it called 'txtSearch'.

You can control the Visibility of a control based on a TextBox being empty by using Text.Length in a DataTrigger:

<TextBox x:Name="txtSearch" />

<TextBlock Text="{Binding Text.Length, ElementName=txtSearch}">
    <TextBlock.Style>
        <Style TargetType="TextBlock">
            <Setter Property="Visibility"
                    Value="Visible" />
            <Style.Triggers>
                <DataTrigger Binding="{Binding Text.Length, ElementName=txtSearch}" Value="0">
                    <Setter Property="Visibility"
                            Value="Hidden" />
                </DataTrigger>
            </Style.Triggers>
        </Style>
    </TextBlock.Style>
</TextBlock>

You could also create a custom EmptyToHidden Converter for this which would not require a Style:

public class EmptyToHidden : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        if (value is string strValue &&
            !string.IsNullOrWhiteSpace(strValue))
        {
            return Visibility.Visible;
        }

        return Visibility.Hidden;
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        throw new NotSupportedException();
    }
}