How to show Enum type members in a DataGridViewComboBox?

Question

What else I have to do in order to show ReadAccess enum members in this DatagridViewComboBox?

ReadDataGridViewComboBoxColumn.Items.Clear();
ReadDataGridViewComboBoxColumn.Items.AddRange(ReadAccess.None, ReadAccess.Allowed);
ReadDataGridViewComboBoxColumn.ValueType = typeof(ReadAccess);

here is designer-generated codes about DataGridView:

this.rolesDataGridView.AutoGenerateColumns = false;
this.rolesDataGridView.Columns.AddRange(new System.Windows.Forms.DataGridViewColumn[] {
this.TableNameDataGridViewTextBoxColumn,
this.ReadDataGridViewComboBoxColumn,
this.WriteDataGridViewComboBoxColumn,
this.ReadCodeDataGridViewComboBoxColumn,
this.ProcessDataGridViewCheckBoxColumn,
this.AdministrateDataGridViewCheckBoxColumn});
this.rolesDataGridView.DataSource = this.bsTablePermissions;

and finally, in after InitializeComponent();, i'm setting DataGridView's DataSource:

this.rolesDataGridView.DataSource = this.RoleTablePermissions;  // a bindingsource list

Answer 1

This is a problem i've come across many times. The DataGridViewComboBoxColumn doesn't know how to reconcile the difference between the enum's string representation and its integral value. Even though you set ValueType to the type of the enum, the DataGridView will try to set the cell's value to the underlying int value - this is why a FormatException will be raised during databinding.

The only way i've found to overcome this problem (short of subclassing the cell type) is to bind the DataGridViewComboBoxColumn to a data source which separates the string values from the integer values. You can use an anonymous type for this purpose:

ReadDataGridViewComboBoxColumn.ValueType = typeof(ReadAccess);
ReadDataGridViewComboBoxColumn.ValueMember = "Value";
ReadDataGridViewComboBoxColumn.DisplayMember = "Display";
ReadDataGridViewComboBoxColumn.DataSource = new ReadAccess[]
    { ReadAccess.None, ReadAccess.Allowed }
    .Select(value => new { Display=value.ToString(), Value=(int)value })
    .ToList();

This way, the DataGridView knows how to relate the cell value with its formatted value.