.NET MAUI [ObservableProperty] decimal shows fixed decimals in UI — need fully dynamic decimal places (0–10)

Question

I'm building a .NET MAUI app using the CommunityToolkit.Mvvm [ObservableProperty] attribute for data binding.

Example:

[ObservableProperty]
public decimal _count;

Setting the value:

decimal count = 2;
Item.Count = count;

If Count is a normal property, the UI shows 2 as expected.

But when using [ObservableProperty], the UI shows 2.000.

I need the number of decimal places to be fully dynamic:

If it's an integer value → show 2
If it's 2.5 → show 2.5
If it's 2.1234567890 → show exactly that (up to 10 decimals in my case)

I cannot hardcode a format like "0.##" because the number of decimal places changes depending on other data in the object.

Question: why is [ObservableProperty] changing the formatting in the UI, and how can I keep the property observable while showing a completely dynamic number of decimal places?

Notes:

Item is part of my view model.
I'm using .NET MAUI and CommunityToolkit.Mvvm.
Formatting should reflect the actual decimal value — no forced trailing zeros.
The formatting issue only happens with [ObservableProperty] or INotifyPropertyChanged

Edit:

Here is the Code for my UI:

<CollectionView Grid.Row="1"
                ItemsSource="{Binding Items}"
                SelectedItem="{Binding SelectedItem}"
                SelectionMode="Single"
                EmptyView="No Data"
                ItemSizingStrategy="MeasureFirstItem"
                x:Name="List">
    <CollectionView.ItemTemplate>
        <DataTemplate>
            <VerticalStackLayout>
           
            <Grid ColumnDefinitions=".5*, .25*, .25*"
                      Padding="8,8,8,8"
                      RowSpacing="8" HeightRequest="40">
                <Label Text="{Binding Name}" Grid.Column="0" FontSize="12" VerticalOptions="Center" HorizontalOptions="Start"/>
                <Label Text="{Binding Name2}" Grid.Column="1" FontSize="12" VerticalOptions="Center" HorizontalOptions="End"/>
                <Label Text="{Binding Count}" Grid.Column="2" FontSize="12" VerticalOptions="Center" HorizontalOptions="End"/>
            </Grid>
            </VerticalStackLayout>
        </DataTemplate>
    </CollectionView.ItemTemplate>
</CollectionView>

Please show the UI-side code for both your cases (with and without ObservabelPropertyAttribute) — Serg
– Serg, Commented Aug 14 at 18:05
Can I do this dynamically? If the property isn’t observable I can set the variable to 2 or 2.00 and it gets displayed the way I set it — Joshie
– Joshie, Commented Aug 14 at 22:32
Use the "G" format specifier; e.g. public string CountDisplay => $"{count:G}"; — Gerry Schmitz
– Gerry Schmitz, Commented Aug 15 at 2:43

user17746682 · Accepted Answer · 2025-08-16 08:48:51Z

It may be time to move away from the [ObservableProperty] and use the field contextual keyword. It is part of C#13 and can be used in preview. Edit your project file and set.

<LangVersion>preview</LangVersion>

C#14 will be out in a few months.

Below are some properties that I use that require a property change notification

public string? Image { get => field; set => Notify(ref field, value); }
public string? Description { get; set => Notify(ref field, value); }
public decimal? Amount { get; set => Notify(ref field, value); }

public event PropertyChangedEventHandler? PropertyChanged;
public void Notify<V>(ref V to, V from, [CallerMemberName] string property = "")
{
    if (property == null)
    {
        return;
    }

    if (to == null && from == null)
    {
        return;
    }

    if (to != null && to.Equals(from))
    {
        return;
    }

    to = from;
    PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(property));
}

I reference the field contextual keyword in the get accessor of the Image property although a get accessor that does not specify a backing field will automatically return field.

https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/keywords/field

Joshie · Accepted Answer · 2025-08-26 10:18:51Z

0

Everything I tried didn't work until I did this. I expanded my Object cointaining Count with the Properties DecimalPlaces and CountDisplay. Then I did this:

[ObservableProperty]
public decimal _count;
public int DecimalPlaces => DecimalPlacesHelper.GetDecimalPlaces(this);
public string CountDisplay => Count.ToString($"F{DecimalPlaces }");

partial void OnCountChanged(decimal value)
{
    OnPropertyChanged(nameof(CountDisplay));
}

answered Aug 26 at 10:18

Joshie

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