How to get time only from DateTime in wpf?

I have this method which is meant to parse and get the time that the user types in the textBox in WPF.
It should then add a string like '12:05' as a value to one of my selected items.

   private void addInterviewTime(object sender, RoutedEventArgs e)  
           {  
               ShortlistedClient sc = dgr.SelectedItem as ShortlistedClient;  
     
     
               if (sc != null && DateTime.TryParseExact(textBox.Text, "HH: mm", out TimeOnly result))  
               {  
                   sc.DT = result;  
               }  
     
           }  

It gives the following errors:

   // for this line, if (sc != null && DateTime.TryParseExact(textBox.Text, "HH: mm", out TimeOnly result))  
   Error	CS1501	No overload for method 'TryParseExact' takes 3 arguments  
     
   // and for	 sc.DT = result;  
     
   Error	CS0029	Cannot implicitly convert type 'System.TimeOnly' to 'System.DateTime?'  

I have also tried

   if (sc != null && TimeOnly.TryParseExact(textBox.Text, "HH: mm", out TimeOnly result))  
               {  
                   sc.DT = result;  
               }  

and it still gives

   Error	CS0029	Cannot implicitly convert type 'System.TimeOnly' to 'System.DateTime?'  

Previously, I have set my DT property like this in my ShortlistedClient class:

   public class ShortlistedClient : Client, INotifyPropertyChanged  
       {  
           private DateTime? _dt;  
     
           public DateTime?  DT  
           {  
               get { return _dt; }  
               set { _dt = value; NotifyPropertyChanged(); }  
           }  
     
           public bool InterestedinVac { get; private set; }  
           
     
           public List<ShortlistedClient> clients { get; set; } = new List<ShortlistedClient>();  
           public ShortlistedClient(string n, string p, string e, string l, string wt, string q, string we, string dl, string cc) : base(n, p, e, l, wt, q, we, dl, cc)  
           {  
               DT = new DateTime();   
               InterestedinVac = true;   
           }  

how can I have time only and fix these errors?