C# ComboBox extension method Suggest Append By any string

[make me rain]

I wanted to have an extension method to Combobox control which suggest the combobox list items by any part of the string. rather than the first part of the list items. i have done some coding but which is failing
(1) Auto suggest not appearing
(2) Combo box texts are over writing, i mean only one character remaining in the text field.
(3) Some times, the Horrible Happens

System.AccessViolationException: 'Attempted to read or write protected memory. This is often an indication that other memory is corrupt.'

public static void AutoCompleteByAnyString(this ToolStripComboBox CboBx,
                                                    DataTable SourceTable,
                                                    string Q )
        {            
 
 
            if (Q.Length > 0 && SourceTable != null)
            {                
 
 
                var Fs = (from Dr in SourceTable.AsEnumerable()
                               where Dr.Field<String>("Fs").Contains(Q.ToUpper())
                               select Dr [CboBx.ComboBox.DisplayMember]).ToArray();
 
 
                
 
 
                AutoCompleteStringCollection A = new AutoCompleteStringCollection();
                foreach (var item in Fs)
                {
                    A.Add(item.ToString());
                }
 
 
                CboBx.AutoCompleteSource = AutoCompleteSource.CustomSource;
                CboBx.AutoCompleteCustomSource = A;               
               CboBx.AutoCompleteMode = AutoCompleteMode.Suggest; 
                
            } else
            {
                CboBx.AutoCompleteSource = AutoCompleteSource.ListItems;
                CboBx.AutoCompleteMode = AutoCompleteMode.SuggestAppend;
            }
            
        }
[COLOR=#242729][FONT=Arial][/FONT][/COLOR]

The above code should have displayed the suggested list items in the combobox.
Note: i am using VS2019