public static GridColumn AddDropDownColumn <T>(this GridView view, Func <T, object> value, IEnumerable <object> dataStore, IIndirectBinding <string> textBinding, string header, bool editable = false)
{
var internalBinding = Binding.Delegate(value);
Cell cell;
// hack for eto/gtk not supporting ItemTextBinding on ComboBoxCells
if (Platform.Instance.IsGtk)
{
const char zws = '\u200B'; // This is a zero width (ZWS) space Unicode character.
var lDataStore = dataStore.ToList();
var tDataStore = lDataStore.Select(i =>
string.Empty.PadLeft(lDataStore.IndexOf(i) + 1, zws) // Pad with index+1 ZWS chars to be able to check later. If no ZWS is there, this did not work.
+ textBinding.GetValue(i))
.ToList();
var hasNonUnique = tDataStore.Distinct().Count() != tDataStore.Count; // Check if textBinding produced the same string for more than one data item.
var binding = Binding.Delegate <T, string>(
(T s) => textBinding.GetValue(internalBinding.GetValue(s)),
(T t, string s) =>
{
int idx = s.Split(zws).Length - 2;
if (idx == -1)
{
idx = tDataStore.IndexOf(s); // Fallback if ZWS is not supported.
if (hasNonUnique)
{
throw new Exception("ComboBoxCell ComboTextBinding Polyfill: Duplicate text entry encountered and Zero-Width-Space Hack not supported by platform!");
}
}
internalBinding.SetValue(t, lDataStore[idx]);
}).Cast <object>();
cell = new ComboBoxCell {
Binding = binding, DataStore = tDataStore
};
}
else
{
cell = new ComboBoxCell {
Binding = internalBinding, DataStore = dataStore, ComboTextBinding = textBinding
}
};
return(view.AddColumn(cell, header, editable));
}
