How can I populate a list with values from a SQL Server database?

The list will grow and shrink depending on how many items I have in my database.

I need to populate a list not a listbox. I understand I will need to open a connection.

using (var conn = new SqlConnection(Properties.Settings.Default.DBConnectionString))
 {
     using (var cmd = conn.CreateCommand())
     {
         conn.Open(); 
 
         List<string> TagList = new List<string>();
         for (int i = 0; i < TagList.Count; i++)
             TagList[i].Add("Data from database");
 
         cmd.ExecuteNonQuery();
     }
 }
 

I'm really not sure how to do this and I'm sure my method up here looks very wrong so I really need help.

Could someone show me what I'm doing wrong?

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