How to insert 'Empty' field in ComboBox bound to DataTable

Question

I have a combo box on a WinForms app in which an item may be selected, but it is not mandatory. I therefore need an \'Empty\' first item to indicate that no value has been s

Answer 1

cmbHierarchies.SelectedIndex = -1;

Answer 2

There are two things you can do:

1. Add an empty row to the DataTable that is returned from the stored procedure.

   DataRow emptyRow = hierarchies.NewRow();
   emptyRow["guid"] = "";
   emptyRow["ObjectLogicalName"] = "";
   hierarchies.Rows.Add(emptyRow);
   

   Create a DataView and sort it using ObjectLogicalName column. This will make the newly added row the first row in DataView.

   DataView newView =           
        new DataView(hierarchies,       // source table
        "",                             // filter
        "ObjectLogicalName",            // sort by column
        DataViewRowState.CurrentRows);  // rows with state to display
   

   Then set the dataview as DataSource of the ComboBox.

2. If you really don't want to add a new row as mentioned above. You can allow the user to set the ComboBox value to null by simply handling the "Delete" keypress event. When a user presses Delete key, set the SelectedIndex to -1. You should also set ComboBox.DropDownStyle to DropDownList. As this will prevent user to edit the values in the ComboBox.

Answer 3

I would bind the data then insert an blank item at position 0 using the ComboxBox.Items.Insert method. Similar to what flipdoubt suggested, but it adds the item to the top.

Answer 4

Cant you add a new DataRow to the DataTable before you bind it to your DataSource?

You can use the NewRow function of the DataTable to achieve this:

http://msdn.microsoft.com/en-us/library/system.data.datatable.newrow.aspx

Answer 5

Er, can't you just add a default item to the ComboBox after data binding?

Answer 6

insert a blank row in your datatable, and check for it in validation/update/create