在wpf datagrid中itemssource为null时显示空行

Question

I am working on a project in wpf with mvvm. I just want to show a row on a wpf datagrid to add a new item and i have an ItemsSource but it is null and canUserAddRows is set to true.

Thanks in advance.

Answer 1

You need some kind of ItemsSource that is not null . Just initialize your ObservableCollection<yourType> .

Easiest is to do it via constructor of your ViewModel:

public class ViewModel : INotifyPropertyChanged
{
     public ViewModel()
     {
          _yourCollection = new ObservableCollection<yourType>();
          //Now Items can be added, via code behind, or UI !
     }
}

Think of it : You cannot call .Add() on a null object (would throw NullReferenceException ). So how should the control itself allow that via UI - there is nothing to store the values in !

Example:

ViewModel:

public class ViewModel 
{

     public ObservableCollection<Model> Collection { get; set;}         

     public ViewModel()
     {
          Collection = new ObservableCollection<Model>();
          //Now Items can be added, via code behind, or UI !
     }
}

Model:

public class Model
{
    public string Text { get; set; }
}

Xaml:

<DataGrid CanUserAddRows="True"
          AutoGenerateColumns="False"
          IsReadOnly="False"
          ItemsSource="{Binding Collection}">
    <DataGrid.Columns>
        <DataGridTextColumn Width="*" 
                            Header="Value" 
                            Binding="{Binding Text}"/>
    </DataGrid.Columns>
</DataGrid>

Result: