Data not displaying in desired format..

Date based formatting only works on date based values: strings are not date based, and can contain anything.

The problem is your database (or how you interpret data from your database) - you need to change it so that date based date is stored in date based fields, numerics in appropriate numeric datatypes, and so on: if you might need to sort data, do maths with data, or do anything real-world with it, you need to stroie it in appropriate datatypes. This is including displaying it since the user selected Locale should be in charge of the format used for both input and output of such data.

Change your data source: you will probably find a load of data errors or ambiguity has already crept in, and that problem will only get worse the longer you leave it!

private string _bDt;

public string BDt

{
 get {
 DateTime dt;
 var b = DateTime.TryParse(_bDt, out dt);
 return b ? dt.ToString("yyyy-MM-dd") : _bDt;
}

set {   SetValue(ref _bDt, value); }}