VB.NET ต้องการหาค่าที่อยู่ในแต่ละ List ว่าอยู่ที่ List ไหน ตำแหน่งไหน

If a1.Contains(textbox1.Text) Then
            TextBox2.Text = "true"
        Else
            TextBox2.Text = "false"
        End If

using System;
using System.Collections.Generic;
					
public class Program
{
	public static void Main()
	{
		List<string> a1 = new List<string> {"123", "231", "312", "321"};
		List<string> a2 = new List<string> {"456", "564", "645", "654"};
		List<string> a3 = new List<string> {"789", "897", "978", "987"};
		Dictionary<string, List<string>> data = new Dictionary<string, List<string>> {
			{"a1", a1},
			{"a2", a2},
			{"a3", a3}
		};
		
		string test = "312";
		string res = string.Empty;
		
		foreach(KeyValuePair<string, List<string>> item in data) {
			int t = item.Value.IndexOf(test);
			if (t != -1) {
				res = item.Key + " " + t.ToString();
				break;
			}
		}
		
		Console.WriteLine(res);
	}
}

Imports System
Imports System.Collections.Generic

Public Class Program
    Public Shared Sub Main()
        Dim a1 As List(Of String) = New List(Of String) From { "123", "231", "312", "321"}
        Dim a2 As List(Of String) = New List(Of String) From { "456", "564", "645", "654"}
        Dim a3 As List(Of String) = New List(Of String) From { "789", "897", "978", "987"}
        Dim data As Dictionary(Of String, List(Of String)) = New Dictionary(Of String, List(Of String)) From {
            {"a1", a1},
            {"a2", a2},
            {"a3", a3}
        }
        Dim test As String = "312"
        Dim res As String = String.Empty

        For Each item As KeyValuePair(Of String, List(Of String)) In data
            Dim t As Integer = item.Value.IndexOf(test)

            If t <> -1 Then
                res = item.Key & " " & t.ToString()
                Exit For
            End If
        Next

        Console.WriteLine(res)
    End Sub
End Class