The main form:
fDocForm fDocForm = new fDocForm()
fDocForm.ShowDialog();
if(fDocForm.DialogResult!=null)
//use of id returned from dialog form
else
MessageBox.Show("null");
in the dialog form:
private void button1_Click(object sender, EventArgs e)
{
//insert sql command and returned id of inserted recored
DialogResult = DialogResult.OK;
this.Hide();
}
how could I return the id value from the dialog form to the main form?
One option is to pass data from child form to parent form using an event which is invoked when clicking a button on the child form, data is in a validate state invoke the event then set DialogResult to OK.
The following is a conceptual example where the main form opens a child form for adding a new item of type Note.
If all you need is a single property/value this will still work by changing the delegate signature OnAddNote.
Note class
public class Note : INotifyPropertyChanged
{
private string _title;
private string _content;
private int _id;
public int Id
{
get => _id;
set
{
_id = value;
OnPropertyChanged();
}
}
public string Title
{
get => _title;
set
{
_title = value;
OnPropertyChanged();
}
}
public string Content
{
get => _content;
set
{
_content = value;
OnPropertyChanged();
}
}
public override string ToString() => Title;
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
}
Operations class
NewNote method is called from the child form Add button when data is validated
public class Operations
{
public delegate void OnAddNote(Note note);
public static event OnAddNote AddNote;
public static List<Note> NotesList = new List<Note>();
/// <summary>
/// Pass new Note to listeners
/// </summary>
/// <param name="note"></param>
public static void NewNote(Note note)
{
AddNote?.Invoke(note);
}
/// <summary>
/// Edit note, do some validation
/// </summary>
/// <param name="note"></param>
/// <returns></returns>
public static Note EditNote(Note note)
{
throw new NotImplementedException();
}
/// <summary>
/// Load mocked data, for a real application if persisting data use <see cref="LoadNotes"/>
/// </summary>
public static void Mocked()
{
NotesList.Add(new Note()
{
Title = "First",
Content = "My note"
});
}
/// <summary>
/// For a real application which persist your notes we would load from
/// - a database
/// - file (xml, json etc)
/// </summary>
/// <returns></returns>
public static List<Note> LoadNotes()
{
throw new NotImplementedException();
}
/// <summary>
/// Delete a note in <see cref="NotesList"/>
/// </summary>
/// <param name="note"></param>
public static void Delete(Note note)
{
throw new NotImplementedException();
}
public static Note FindByTitle(string title)
{
throw new NotImplementedException();
}
/// <summary>
/// Save data to the data source loaded from <see cref="LoadNotes"/>
/// </summary>
/// <returns>
/// Named value tuple
/// success - operation was successful
/// exception - if failed what was the cause
/// </returns>
public static (bool success, Exception exception) Save()
{
throw new NotImplementedException();
}
}
Child form
public partial class AddNoteForm : Form
{
public AddNoteForm()
{
InitializeComponent();
}
private void AddButton_Click(object sender, EventArgs e)
{
if (!string.IsNullOrWhiteSpace(TitleTextBox.Text) && !string.IsNullOrWhiteSpace(NoteTextBox.Text))
{
Operations.NewNote(new Note() {Title = TitleTextBox.Text, Content = NoteTextBox.Text});
DialogResult = DialogResult.OK;
}
else
{
DialogResult = DialogResult.Cancel;
}
}
}
Main form
public partial class Form1 : Form
{
private readonly BindingSource _bindingSource = new BindingSource();
public Form1()
{
InitializeComponent();
Shown += OnShown;
}
private void OnShown(object sender, EventArgs e)
{
Operations.AddNote += OperationsOnAddNote;
Operations.Mocked();
_bindingSource.DataSource = Operations.NotesList;
NotesListBox.DataSource = _bindingSource;
ContentsTextBox.DataBindings.Add("Text", _bindingSource, "Content");
}
private void OperationsOnAddNote(Note note)
{
_bindingSource.Add(note);
NotesListBox.SelectedIndex = NotesListBox.Items.Count - 1;
}
private void AddButton_Click(object sender, EventArgs e)
{
var addForm = new AddNoteForm();
try
{
addForm.ShowDialog();
}
finally
{
addForm.Dispose();
}
}
}
You can store the id in a public property of the dialog, and the access that property from the main form.
