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Comments on C# WPF MVVM View & Get new record values

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C# WPF MVVM View & Get new record values

−0

Just looking to hear some reviews on my current MVVM Implementation, If I am heading towards the right direction. :)

Code

BaseViewModel

public class BaseViewModel : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;

    protected void OnPropertyChanged(string propertyName)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }
    }
}

ViewModel

public class Technical_BestBeforeDates_ViewModel : BaseViewModel
{

    // Loading + Filtering Data
    private string _ProductCode;
    public string ProductCode
    {
        get { return _ProductCode; }
        set
        {
            _ProductCode = value;
            OnPropertyChanged(nameof(ProductCode));
            UpdateDataFromDatabase();
        }
    }

    private string _ProductDescription;
    public string ProductDescription
    {
        get { return _ProductDescription; }
        set
        {
            _ProductDescription = value;
            OnPropertyChanged(nameof(ProductDescription));
            UpdateDataFromDatabase();
        }
    }

    public ObservableCollection<Technical_BestBeforeDates_Model> BestBeforeDates_Models { get; }

    public void UpdateDataFromDatabase()
    {
        BestBeforeDates_Models.Clear();

        var records = Technical_BestBeforeData.GetFilteredData(ProductCode, ProductDescription);
        foreach (Technical_BestBeforeDates_Model model in records)
        {
            BestBeforeDates_Models.Add(model);
        }
    }

    // Open New Window Command
    public ICommand OpenCreateNewRecordCommand { get; set; }

    public void OpenWindow()
    {
        Technical_BestBeforeDates_CreateNewView window = new Technical_BestBeforeDates_CreateNewView()
        {
            WindowStartupLocation = System.Windows.WindowStartupLocation.CenterScreen,
            DataContext = new Technical_BestBeforeDates_CreateNewViewModel()
        };
        window.ShowDialog();
    }


    // Constructor
    public Technical_BestBeforeDates_ViewModel()
    {
        BestBeforeDates_Models = new ObservableCollection<Technical_BestBeforeDates_Model>();

        UpdateDataFromDatabase();

        OpenCreateNewRecordCommand = new RelayCommand(_ => OpenWindow());
    }
}

CreateNewViewModel

public class Technical_BestBeforeDates_CreateNewViewModel : BaseViewModel
{

    private Technical_BestBeforeDates_Model _NewModel_;

    public Technical_BestBeforeDates_Model NewModel
    {
        get { return _NewModel_; }
        set
        {
            _NewModel_ = value;
            OnPropertyChanged(nameof(NewModel));
        }
    }

    private string _ProductCode;

    public string ProductCode
    {
        get { return _ProductCode; }
        set
        {
            _ProductCode = value;
            NewModel = new Technical_BestBeforeDates_Model
            {
                ProductCode = _ProductCode,
                ProductDescription = this.ProductDescription
            };
            OnPropertyChanged(nameof(ProductCode));
        }
    }

    private string _ProductDescription;

    public string ProductDescription
    {
        get { return _ProductDescription; }
        set
        {
            _ProductDescription = value;
            NewModel = new Technical_BestBeforeDates_Model
            {
                ProductCode = this.ProductCode,
                ProductDescription = _ProductDescription
            };
            OnPropertyChanged(nameof(ProductDescription));
        }
    }

    public ICommand CreateNewRecordCommand { get; set; }

    public void CreateNewRecord(object param)
    {
        var vm = param as Technical_BestBeforeDates_Model;

        System.Windows.MessageBox.Show(vm.ProductCode);
    }

    public Technical_BestBeforeDates_CreateNewViewModel()
    {
        CreateNewRecordCommand = new RelayCommand(param => CreateNewRecord(param));
    }
}

RelayCommand

public class RelayCommand : ICommand
{
    private Action<object> execute;

    private Predicate<object> canExecute;

    private event EventHandler CanExecuteChangedInternal;

    public RelayCommand(Action<object> execute)
        : this(execute, DefaultCanExecute)
    {
    }

    public RelayCommand(Action<object> execute, Predicate<object> canExecute)
    {
        if (execute == null)
        {
            throw new ArgumentNullException("execute");
        }

        if (canExecute == null)
        {
            throw new ArgumentNullException("canExecute");
        }

        this.execute = execute;
        this.canExecute = canExecute;
    }

    public event EventHandler CanExecuteChanged
    {
        add
        {
            CommandManager.RequerySuggested += value;
            this.CanExecuteChangedInternal += value;
        }

        remove
        {
            CommandManager.RequerySuggested -= value;
            this.CanExecuteChangedInternal -= value;
        }
    }

    public bool CanExecute(object parameter)
    {
        return this.canExecute != null && this.canExecute(parameter);
    }

    public void Execute(object parameter)
    {
        this.execute(parameter);
    }

    public void OnCanExecuteChanged()
    {
        EventHandler handler = this.CanExecuteChangedInternal;
        if (handler != null)
        {
            handler.Invoke(this, EventArgs.Empty);
        }
    }

    public void Destroy()
    {
        this.canExecute = _ => false;
        this.execute = _ => { return; };
    }

    private static bool DefaultCanExecute(object parameter)
    {
        return true;
    }
}

Data Storage - Technical_BestBeforeData

public static class Technical_BestBeforeData
{

    private static List<Technical_BestBeforeDates_Model> GetData()
    {
        using (MySqlConnection conn = new MySqlConnection(ConfigurationManager.ConnectionStrings["MySQL"].ConnectionString))
        {
            conn.Open();

            string query = @"SELECT b.id AS Id, 
                                    ProductCode, 
                                    ProductDescription, 
                                    b.AreaID as AreaID,
                                    MinimumMonths,
                                    LAST_DAY(DATE_ADD(NOW(), INTERVAL MinimumMonths MONTH)) AS BestBeforeDate
                                FROM technical_bestbeforedates b"; ;


            var records = conn.Query<Technical_BestBeforeDates_Model>(query).ToList();
            return records;
        }
    }

    private static bool Filter(Technical_BestBeforeDates_Model tbm, string code, string description)
    {
        return (string.IsNullOrEmpty(code) || tbm.ProductCode.Contains(code)) && (string.IsNullOrEmpty(description) || tbm.ProductDescription.Contains(description));
    }
        

    public static IEnumerable<Technical_BestBeforeDates_Model> GetFilteredData(string code, string description)
    {
        return GetData().Where(tbm => Filter(tbm, code, description));
    }
        

}

Model

public class Technical_BestBeforeDates_Model
{
    public int Id { get; set; }
    public string ProductCode { get; set; }
    public string ProductDescription { get; set; }
}

c# mvvm wpf

posted almost 4 years ago

CC BY-NC-SA 4.0

4y ago by FoggyFinder‭

gzi98‭

69 reputation 4 0 13 1

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is a duplicate

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not constructive

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−0

Some thoughts:

Consider using Github (or something like that, but I suggest Github due to its popularity) to share the project. It allows us not only to write some code but open PR with suggestions.
Do not use such names as Technical_BestBeforeDates_Model, etc. Using of _ is against C# style guide. PascalCase is a preferable way.

Besides, it is hard to perceive.

I suppose, for Technical_BestBeforeDates_Model class you probably could:

Use Technical as a name for namespace.
Remove Model part. Put it to a separate Model project to stress its purpose.

So Technical_BestBeforeDates_Model turns to Model.Technical.BestBeforeDates.

In short:

Name should be laconic and, at the same time, meaningfull.

BaseViewModel.

Use CallerMemberName attribute
Use new version of C# to simplify null's check.
To reduce boilerplate code you can add helpful SetProperty method

protected virtual bool SetProperty<T>(ref T storage, T value, [CallerMemberName] string propertyName = "")
{
    if (EqualityComparer<T>.Default.Equals(storage, value))
    {
        return false;
    }
    storage = value;
    this.OnPropertyChanged(propertyName);
    return true;
}

Technical_BestBeforeDates_ViewModel

VM should know nothing about View. Use services or consider using SPA (single page application) approach to navigate between pages.
Be careful with sending a query to DB each time user changes something in a field. You could use Delay, Debounce, etc to prevent spamming. But maybe that's not the case here.

CreateNewViewModel

Use camelCase for fields.
Passing something as a command parameter despite you have direct access to it that's odd.

public class Technical_BestBeforeDates_CreateNewViewModel : BaseViewModel
{
    private string productCode;
    public string ProductCode
    {
        get { return productCode; }
        set { SetProperty(ref productCode, value); }
    }

    private string productDescription;
    public string ProductDescription
    {
        get { return productDescription; }
        set { SetProperty(ref productDescription, value); }
    }

    public ICommand CreateNewRecordCommand { get; set; }

    public void CreateNewRecord()
    {
        var m = new Technical_BestBeforeDates_Model
        {
            ProductCode = productCode,
            ProductDescription = this.ProductDescription
        };

        System.Windows.MessageBox.Show(m.ProductCode);
    }

    public Technical_BestBeforeDates_CreateNewViewModel()
    {
        CreateNewRecordCommand = new RelayCommand(_ => CreateNewRecord());
    }
}

Again, there should be no reference to any type that related to View (like MessageBox)

Technical_BestBeforeData

Name of this class doesn't reflect meaning.
It would be better to filter data on a database side. It's usually faster there.
Name of GetData method also doesn't reflect meaning.
You could move an sql query out of a method to keep them all together.

posted almost 4 years ago

CC BY-NC-SA 4.0

FoggyFinder‭

318 reputation 2 12 33 7

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General comments (1 comment)

elgonzo‭ wrote almost 4 years ago · edited almost 4 years ago

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I am not a fan of backing fields only differing from their associated property names in letter case. It makes it all too easy to write member method code that by accident manipulates the backing field instead of going through the property setter (which for VMs often has side effects such as raising events) and vice versa. Having a backing field with a leading underscore (or other ways of making backing field names visually more distinct from the property names) helps avoid making such mistakes.

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