Skip to content

Latest commit

 

History

History
228 lines (179 loc) · 7.54 KB

09 - WinForms - DataBinding, UnitTesting.md

File metadata and controls

228 lines (179 loc) · 7.54 KB
Raw

Windows Forms – DataBinding and Unit Testing

1. Objectives

  • understand the concept and the utility of data binding;
  • understand the differences between simple and complex data binding;
  • implement simple data binding;
  • implement complex data binding;

2. DataBinding

Data binding types

Type Description
Simple data binding The ability of a control to bind to a single data element, such as a value in a column in a dataset table. This is the type of binding typical for controls such as a TextBox control or Label control, which are controls that typically only displays a single value. In fact, any property on a control can be bound to a field in a database.
Complex data binding The ability of a control to bind to more than one data element, typically more than one record in a database. Complex binding is also called list-based binding. Examples of controls that support complex binding are the DataGridView, ListBox, and ComboBox controls.

Change notification

  • Ensures that your data source and bound controls always have the most recent data, we must add change notification for data binding. Specifically, we want to ensure that bound controls are notified of changes that were made to their data source, and the data source is notified of changes that were made to the bound properties of a control.

Cases:

Activity

:octocat: Full source code available, check the DataBindingSample sample.

  1. Create a copy of the "ListViewBasicSample" project and name it "DataBindingSample"

  2. Replace the “ListView” control with a DataGridView control (Name: dgvParticipants)

  3. Add a “ViewModel” folder to your project

  4. Add the following MainFormViewModel class in the “ViewModel” folder

    internal class MainFormViewModel : INotifyPropertyChanged
{
	#region Properties
	#region LastName
	private string _lastName;
	public string LastName {
		get { return _lastName; }
		set
		{
			if (_lastName == value)
				return;
			_lastName = value;

			//If we use [CallerMemberName] in the OnPropertyChanged method
			//OnPropertyChanged();
			//If we don't use the [CallerMemberName] in the OnPropertyChanged method
			OnPropertyChanged("LastName");
		}
	}
	#endregion

	#region FirstName
	private string _firstName;
	public string FirstName
	{
		get { return _firstName; }
		set
		{
			if (_firstName == value)
				return;
			_firstName = value;
			OnPropertyChanged();
		}
	}
	#endregion

	#region BirthDate
	private DateTime _birthDate;

	public DateTime BirthDate
	{
		get { return _birthDate; }
		set
		{
			if (_birthDate == value)
				return;
			_birthDate = value;
			OnPropertyChanged();
		}
	}
	#endregion

	public BindingList<Participant> Participants { get; set; }
	#endregion

	public MainFormViewModel()
	{
		Participants = new BindingList<Participant>();
		BirthDate = DateTime.Now;
	}

	#region Methods
	public void AddParticipant()
	{
		Participants.Add(new Participant(LastName, FirstName, BirthDate));
		LastName = FirstName = string.Empty;
		BirthDate = DateTime.Today;
	}
	#endregion

	#region INotifyPropertyChanged
	public event PropertyChangedEventHandler PropertyChanged;

	// [CallerMemberName] - Allows you to obtain the method or property name of the caller to the method. https://msdn.microsoft.com/en-us/library/system.runtime.compilerservices.callermembernameattribute%28v=vs.110%29.aspx
	protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
	{
		if(PropertyChanged != null)
			PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
	}
	#endregion
}

  5. Modify the MainForm class as follows.

    public partial class MainForm : Form
{
	private readonly MainFormViewModel _viewModel;

	public MainForm()
	{
		InitializeComponent();
		_viewModel = new MainFormViewModel();
	}

	private void btnAdd_Click(object sender, EventArgs e)
	{
		_viewModel.AddParticipant();
	}
}

  6. Handle the Load event of the MainForm as follows.

    private void MainForm_Load(object sender, EventArgs e)
{
	dgvParticipants.DataSource = _viewModel.Participants;
				
	//tbLastName.DataBindings.Add("Text", _viewModel, "LastName");
	//Recommended (without magic strings):
	tbLastName.DataBindings.Add("Text", _viewModel, nameof(MainFormViewModel.LastName));

	tbFirstName.DataBindings.Add("Text", _viewModel, "FirstName");
	dtpBirthDate.DataBindings.Add("Value", _viewModel, "BirthDate");
}

Further reading about the MVVM pattern: https://msdn.microsoft.com/en-us/library/hh848246.aspx

Assignments (for you to try) 🎮

  1. Add a button to the MainForm that will allow the user to delete the currently selected participant.

    Hint: you can use the DataBoundItem property in order to identify the participant corresponding to the currently selected row.

    For the complete sample, check the DataBindingSample project in the "code samples" folder.

  2. Add a button to the MainForm that will allow the user to edit the currently selected participant using a secondary form (ex: EditForm).

3. Unit Testing

Documentation:

Activity

:octocat: Full source code available, check the DataBindingSample.Tests sample.

  1. Add a new Unit Test project.

  2. Add a reference to the project created above.

  3. Let's test that the AddParticipant() method implemented above is actually adding a participant.

    [TestClass]
public class MainFormViewModelUnitTest
{
	[TestMethod]
	public void AddParticipantTestMethod()
	{
		//Unit testing basics: https://msdn.microsoft.com/en-us/library/hh694602.aspx

		// arrange
		var viewModel = new MainFormViewModel();

		// act
		viewModel.AddParticipant();

		// assert  
		Assert.AreEqual(viewModel.Participants.Count, 1);
	}
}

Assignments (for you to try) 🎮

  1. Implement additional unit test methods (ex: check whether the LastName property of the added participant is correct).

4. Bibliography