我的dataGrid无法清除并且无法刷新

Question

I have two DataGrid, each binding in a dataSource like this :

ItemsSource="{Binding Data, ElementName=EmpSource, Mode=TwoWay}"

The first DataGrid(dgJob), contains Job and the second(dgEmp), the employee linked to the job .

I want to keep all the employees in the EmpSource, and display in the dataGrid, only those who are linked to the selected job in my first datagrid.

So I am doing this in the dgJob selectionChanged event :

dgEmp.ItemsSource = null;
var lstEmp = EmpSource.DataView.OfType<Emp>().Where(ores => ores.IdJob == itmJobSelect.IdJob).ToList();
dgEmp.ItemsSource = lstEmp;

The problem is, the dataGrid is not clearing when I change the selected line in my datagrid with the jobs, so for every job, I display every Employees in the dgEmp, while I should only display those who are connected to the job.

I can delete the line in the xaml, that determine the dataSource, but if I do this, I must refresh the dataGrid when there is a change in the dataSource.

But I don't found how to refresh it(at least for the first time) unless I write the 3 lines each time after a change in dataSource.

Can somebody help me find a solution to my problem?

Thank you.

Answer 1

I recommend you to use MVVM design pattern. You should load your data in view model class and store it in collection which implements INotifyCollectionChanged interface. View model should also implement INotifyPropertyChanged interface.

When your employee collection changes, you should filter second collection as in following code:

Jobs.CollectionChanged += (sender, args) =>
{
    Employees = AllEmployees.Where(c=> c.IdJob == SelectedJob.IdJob);
}

You should also do same thing when SelectedJob changes and DataGrid will be refreshed.

This will work only when you will have implemented property changed notifications and correct binding was specified.

Here's example of property changed implementation which you should write:

public class ViewModel : INotifyPropertyChanged
{
    public IEnumerable<Emp> Employees
    {
       get { return _employees; }
       set
       {
           if (_employees != value)
           {
               _employees = value;
               OnPropertyChanged("Employees");
           }
       }
    }

    /* ... */

    private void OnPropertyChanged(string propertyName)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }
    }
}

You should also assign your view model instance to DataContext for make binding works. For example in code behind file constructor:

public void Page()
{
    DataContext = new ViewModel();
    InitializeComponent();
}