Unable to add new Row in DataGrid UI automatically

Question

I'm unable to add new rows in my DataGrid from UI. Below is my code.

<DataGrid CanUserAddRows="True" Name="dg"  ItemsSource="{Binding list}"  AutoGenerateColumns="False" >
    <DataGrid.Columns>
        <DataGridTextColumn Binding="{Binding Path=.}" Header="Text"/>
        <DataGridTextColumn Binding="{Binding Length}" Header="Length"/>            
    </DataGrid.Columns>
</DataGrid>

list is a list of string in above Binding.Usually when I set CanUserAddRows="True" I was able to add rows on UI automatically in other examples.

My property is as following:

public List<string> list { get; set; }

And before display of DataGrid it has been initialized. So no need to implement INotifyPropertyChanged for this property.

Can someone explain me why the DataGrid is behaving this way? How to achieve desired behavior?

As far I know when you bind a DataGrid you can't add rows manually — Rodolfo, Feb 16 '16 at 17:27
@Rodolfo that example is for DataGridView. not applicable here — Kylo Ren, Feb 16 '16 at 17:32
http://stackoverflow.com/questions/2075644/wpf-datagrid-cannot-add-a-row-when-datasource-is-empty — Rodolfo, Feb 16 '16 at 17:33
http://stackoverflow.com/questions/480098/how-do-i-create-a-new-row-in-wpf-datagrid-when-it-is-bound-to-an-xmldataprovider — Rodolfo, Feb 16 '16 at 17:35
@Rodolfo my ItemSource is not empty so first link is not relative — Kylo Ren, Feb 16 '16 at 17:36
Read the solutions, read about the default constructor of a bound class — Rodolfo, Feb 16 '16 at 17:40
@Rodolfo not my case. the solution is all about empty collections. — Kylo Ren, Feb 16 '16 at 17:43

score 4 · Accepted Answer · answered Feb 16 '16 at 18:31

The problem is that string does not have a parameter-less constructor, so the grid can't create a new instance for the empty grid row that allows the user to add a new row. Further, the grid can't "set" the "." property onto the string.

One option is to create your own class that exposes Text and Length properties:

public class StringMember : INotifyPropertyChanged
{
private string m_actualString;
public string Text
{
    get { return m_actualString; }
    set
    {
        m_actualString = value;
        //OnPropertyChanged("Text");
        //OnPropertyChanged("Length");
    }
}

public int Length { get { return Value.Length; } }

//public event PropertyChangedEventHandler PropertyChanged;        
//protected virtual void OnPropertyChanged(string propertyName = null)
//{
//    PropertyChangedEventHandler handler = PropertyChanged;
//    if (handler != null) handler(this, new PropertyChangedEventArgs(propertyName));
//}

}

Then, your XAML would bind to your properties:

<DataGrid CanUserAddRows="True" Name="dg"  ItemsSource="{Binding list}"  AutoGenerateColumns="False" >
    <DataGrid.Columns>
        <DataGridTextColumn Binding="{Binding Text}" Header="Text"/>
        <DataGridTextColumn Binding="{Binding Length}" Header="Length"/>            
    </DataGrid.Columns>
</DataGrid>

In this case, your "list" property would be List<StringMember> or ObservableCollection<StringMember> instead of string.

so how to deal with the situation where my model classes don't have default constructor def.? will a optional parameter will do? — Kylo Ren, Feb 16 '16 at 18:43
so do you know any work around of this then in which I don't have to create derived/wrapper classes? — Kylo Ren, Feb 16 '16 at 18:58

Unable to add new Row in DataGrid UI automatically

1 Answers1