How to get the count of specific rows visible items in a WPF datagrid?

Question

Say I have a database table with columns ID, Name, Age, Salary etc.

I have a datagrid where I have set the itemsource as EmpDB where EmpDB is an ICollectionView and then in the MainViewModel I set it as

			EmpDB = new ListCollectionView(_allEmps)  
			{  
				Filter = o => ((Employees)o).Name == SelectedItemFromComboBox  
			};  

where class Employees represents the database table (the model), _allEmps is an ObservableCollection<Employees> and SelectedItemFromComboBox is a string property for the selected combo box item.

Now when I select an item from the combo box then the datagrid gets filled with EmpDB items and I can get the row count of the items currently visible in the datagrid and display it on a TextBlock using something like

<TextBlock Text="{Binding EmpDB.Count} ... />  

But I also want to display say the row count of how many of the Employees that are currently shown in the datagrid whose Age is > 50, the first thing that came in my mind is to add a property to the ViewModel.

So I added a property inside my MainViewModel class and binded it to a textblock

		private int _empcount;  
  
		public int EmpCount  
		{  
			get  
			{  
				if (_empcount == 0) _empcount = _allEmps.Where(x => x.Age > 50).Count();  
  
				return _empcount;  
  
			}  
  
			set  
			{  
				if (_empcount != value)  
				{  
					_empcount = value;  
					OnPropertyChanged("EmpCount");  
				}  
			}  
		}  

The problem is when I launch the app the textblock text bound to EmpCount should be 0 (the datagrid is empty as I have not selected any item from the combo box yet) but I get the count of all Employees whose Age > 50 and that count does not change when I select a different or any combo box item.

What am I missing and where ? Can anyone show me how to fix it ?

Answer 1

MainViewModel :

 public class MainViewModel : ViewModelBase  
    {  
        public ObservableCollection<string> ComboItems { get; set; }  

        public ICollectionView EmpDB { get; set; }  
        public ObservableCollection<Employees> _allEmps { get; set; }  


        private string _SelectedItemFromComboBox;  
        public string SelectedItemFromComboBox  
        {  
            get { return _SelectedItemFromComboBox; }  
            set  
            {  
                SetValue(ref _SelectedItemFromComboBox, value);  

                EmpDB.Refresh();  
                OnPropertyChanged("EmpCount");  
            }  
        }  
        public int EmpCount  
        {  
            get  
            {  
                return EmpDB.OfType<Employees>().ToList().Where(x => x.Age > 50).Count();  

            }  

        }  
        public MainViewModel()  
        {  
            DataAccess d = new DataAccess();  

            _allEmps = d.Emp;  

            ComboItems = new ObservableCollection<string>(_allEmps.Select(b => b.Name).Distinct().OrderBy(b => b).ToList());  

            EmpDB = new ListCollectionView(_allEmps)  

            {  
                Filter = o => ((Employees)o).Name == SelectedItemFromComboBox  
            };  
        }  
 }  

The result:

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Answer 2

As I understand you need to display datagrid row count on text block.

<TextBlock
Content="{Binding ElementName=DataGrid, Path=Items.Count}" />