Unable to create and save json file from SaveFileDialog

Question

I've created a user interface with a save button to allow user export the current configuration into the desired location using a .json file.

This is my button:

<Button Height="25" Margin="5, 0, 0, 0" Width="50" Command="{Binding SaveConfigurationCommand}">
    <Button.Content>
        <Border CornerRadius="5">
            <TextBlock Text="Save" FontSize="10" Foreground="White"/>
        </Border>
    </Button.Content>
</Button>

And this is my viewModel:

private DelegateCommand saveConfigurationCommand;
public DelegateCommand SaveConfigurationCommand =>
    saveConfigurationCommand ?? (saveConfigurationCommand = new DelegateCommand(ExecuteSaveConfigurationCommand));

void ExecuteSaveConfigurationCommand()
{
    try
    {
        SaveFileDialog saveFileDialog = new SaveFileDialog();

        saveFileDialog.Filter = "json files (*.json)|";
        saveFileDialog.InitialDirectory = Path.GetFullPath(Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "..\\..\\..\\Configuration"));

        if (saveFileDialog.ShowDialog() == true)
        {
            Configuration configuration = new Configuration
            {
                Weight = total_weight,
                Animals = new List<Container>(animals),
                Items = new List<Item>(Items)
            };
            File.WriteAllText(saveFileDialog.FileName, Newtonsoft.Json.JsonConvert.SerializeObject(configuration));
        }
    }

    catch (Exception ex)
    {
        MessageBox.Show(ex.Message, "Save configuration error", MessageBoxButton.OK, MessageBoxImage.Error);
    }
}

The problem is, saveFileDialog.FileName is always empty. What I'm doing wrong?