ComboBox column in WPF DataGrid with DataTable as ItemsSource

Question

I've got a datagrid bound to a datatable, with a ComboBoxColumn. The XAML for this column is as follows:

<DataGridComboBoxColumn Header="Rep Name" SortMemberPath="RepName" 
                      ItemsSource="{Binding UpdateSourceTrigger=PropertyChanged, Source={StaticResource EmployeeList}, Path=Employees}"
                      SelectedValueBinding="{Binding Mode=TwoWay, Path=EmpId}"
                      SelectedValuePath="EmpId" DisplayMemberPath="RepName" />

My Employees class:

public class EmployeeList : INotifyPropertyChanged
    {
        private ObservableCollection<Employee> _employees = new ObservableCollection<Employee>();

        public EmployeeList()
        {
           ...
        }

        public ObservableCollection<Employee> Employees
        {
            get { return _employees; }
            set { _employees = value; NotifyPropertyChanged("Employees"); }
        }

        public event PropertyChangedEventHandler PropertyChanged;

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

    public class Employee : INotifyPropertyChanged
    {
        private int _id;
        public int EmpId
        {
            get { return _id; }
            set { _id = value; OnPropertyChanged("EmpId"); }
        }

        public string RepName { get; set; }

        public event PropertyChangedEventHandler PropertyChanged;
        private void OnPropertyChanged(string propertyName)
        {
            if (PropertyChanged != null)
                PropertyChanged(this,
                    new System.ComponentModel.PropertyChangedEventArgs(propertyName));
        }
    }

The DataTable serving as items source for the grid contains an "EmpId" column and a "RepName" column. The combobox is populated with all my employees, and when I make a selection, it is reflected in the datatable. However, when the screen loads, the currently assigned employee is not selected by default in the combobox. I thought that the SelectedValueBinding property of the combobox would handle this... what am I doing wrong?

Update for clarification:
The datagrid is bound to a datatable which includes an EmployeeID column. Let's assume that when the screen loads, there are three rows in the table with EmployeeIDs 1, 2, and 3. I need the combobox column in the first row to have EmployeeID 1 selected, the second row to have EmployeeID 2 selected, and the third row to have EmployeeID 3 selected.

Just curious, are there any databinding errors in the output window when you run? — Ashley Grenon

Ashley Grenon Ashley Grenon · Accepted Answer · 2011-05-11T17:31:39

If I understand your problem correctly, the ComboBox doesn't select the first item in the collection by default?

If that's the case, you should set the property IsSychronizedWithCurrentItem on the ComboBox to true. Info about Selector.IsSynchronizedWithCurrentItem here.

...

Well, unfortunately upon further research, DataGridComboBoxColumn does not have a IsSynchronizedWithCurrentItem property. :/ But, you can create a DataGridTemplateColunm that looks something like this:

<DataGridTemplateColumn Header="Rep Name">
    <DataGridTemplateColumn.CellTemplate>
        <DataTemplate>
            <ComboBox ItemsSource="{Binding Employees}" 
                   IsSynchronizedWithCurrentItem="true" />
        </DataTemplate>
    </DataGridTemplateColumn.CellTemplate>
</DataGridTemplateColunm>

Hope that helps!

ComboBox column in WPF DataGrid with DataTable as ItemsSource

1 Answers