Placeholder text is 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 taggedvalue "Placeholder" along with the desired text to show "Enter a search string..." - this will be 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.

In Turnkey this has been available since early 2022

In WPF you will need to add code - since the out-of-the-box controls of WPF does not support placeholder texts.

If you use the MaterialDesign package this code will ge the effect: