Placeholder text is the text shown as a hint to the User while the control is empty. As soon as the User enters a value, the placeholder text is not shown.
The old way was a <a href="/Documentation:TaggedValues" title="Documentation:TaggedValues" data-bs-title="Documentation:TaggedValues">taggedvalue</a> "Placeholder" along with the desired text to show "Enter a search string..." - this is deprecated.
The new way is to name an additional column with postfix _Placeholder in its name. The result of the expression will be used as a placeholder text.
This has been available in Turnkey since early 2022.
In WPF, you need to add code, since the out-of-the-box controls of WPF do not support placeholder texts.
If you use the excellent MaterialDesign (<a target="_blank" rel="nofollow noreferrer noopener" class="external text" href="http://materialdesigninxaml.net/">MaterialDesignThemes by James Willock)</a> package, this code will get the effect:
_wecpof = new WECPOFTabBased();
...
_wecpof.OnAddWindow += (s, e) =>
{
e.Win.ViewModelUC.OnViewModelColumnPlacementDone += (s2, e2) =>
{
if (e2.Ctrl is System.Windows.Controls.TextBox || e2.Ctrl is System.Windows.Controls.ComboBox || e2.Ctrl is System.Windows.Controls.DatePicker)
{
var val = e2.Vcol.TaggedValueLocalAndModelInfo("Placeholder");
if (!string.IsNullOrEmpty(val))
MaterialDesignThemes.Wpf.HintAssist.SetHint(e2.Ctrl, val);
var dataForPlaceholder = e2.Vcol.ViewModelClass.ColumnFromName(e2.Vcol.RuntimeName + "_Placeholder");
if (dataForPlaceholder != null)
{
if (e2.Ctrl is FrameworkElement)
{
var b = new System.Windows.Data.Binding(dataForPlaceholder.RuntimeName) { Source = e2.Vcol.ViewModelClass.BindingSource, Mode = System.Windows.Data.BindingMode.OneWay /*, Converter = new Eco.Xaml.PassthroughDebugConverter() */ };
(e2.Ctrl as FrameworkElement).SetBinding(MaterialDesignThemes.Wpf.HintAssist.HintProperty, b);
}
}
}
};