C # - DataGridView cannot add row?

Question

I have a simple C # Windows Forms application that should display a DataGridView. I used Object as the DataBinding (I chose the Car class), and it looks like this:

class Car { public string color { get; set ; } public int maxspeed { get; set; } public Car (string color, int maxspeed) { this.color = color; this.maxspeed = maxspeed; } } 

However, when I set the DataGridView property of AllowUserToAddRows to true , there is still little *, which allows me to add rows.

Someone suggested setting carBindingSource.AllowAdd to true , however, when I do this, I get a MissingMethodException that says my constructor was not found.

Answer 1

Your Car class should have a parameterless constructor and your data source should be something like a BindingList

Change the Car class to this:

 class Car { public string color { get; set ; } public int maxspeed { get; set; } public Car() { } public Car (string color, int maxspeed) { this.color = color; this.maxspeed = maxspeed; } } 

And then bind something like this:

 BindingList<Car> carList = new BindingList<Car>(); dataGridView1.DataSource = carList; 

You can also use BindingSource for this, you do not have to, but BindingSource provides some additional functions that may sometimes be needed.

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If for some reason you absolutely cannot add a constructor without parameters, you can handle adding a new binding source event and call the constructor parameterized by Car:

Binding Setting:

 BindingList<Car> carList = new BindingList<Car>(); BindingSource bs = new BindingSource(); bs.DataSource = carList; bs.AddingNew += new AddingNewEventHandler(bindingSource_AddingNew); bs.AllowNew = true; dataGridView1.DataSource = bs; 

And the handler code:

 void bindingSource_AddingNew(object sender, AddingNewEventArgs e) { e.NewObject = new Car("",0); } 

Answer 2

You need to add the AddingNew event handler:

 public partial class Form1 : Form { private BindingSource carBindingSource = new BindingSource(); public Form1() { InitializeComponent(); } private void Form1_Load(object sender, EventArgs e) { dataGridView1.DataSource = carBindingSource; this.carBindingSource.AddingNew += new AddingNewEventHandler(carBindingSource_AddingNew); carBindingSource.AllowNew = true; } void carBindingSource_AddingNew(object sender, AddingNewEventArgs e) { e.NewObject = new Car(); } } 

Answer 3

I recently discovered that if you implement your own binding list using an IBindingList , you MUST return true in your SupportsChangeNotification in addition to AllowNew .

The MSDN article for DataGridView.AllowUserToAddRows indicates only the following note:

If the DataGridView is bound to data, the user is allowed to add rows if this property and data source have the IBindingList.AllowNew property set to true.