是的，C# SQLHelper 可以連接多個數據庫。要實現這個功能，您需要為每個數據庫創建一個單獨的連接字符串，并在創建 SqlHelper 實例時使用相應的連接字符串。以下是一個簡單的示例：

using System;
using System.Data;
using System.Data.SqlClient;

public class SQLHelper
{
    private string _connectionString;

    public SQLHelper(string connectionString)
    {
        _connectionString = connectionString;
    }

    public DataTable ExecuteQuery(string query)
    {
        using (SqlConnection connection = new SqlConnection(_connectionString))
        {
            connection.Open();
            using (SqlCommand command = new SqlCommand(query, connection))
            {
                using (SqlDataReader reader = command.ExecuteReader())
                {
                    DataTable result = new DataTable();
                    result.Load(reader);
                    return result;
                }
            }
        }
    }
}

class Program
{
    static void Main(string[] args)
    {
        string connectionString1 = "Server=Server1;Database=Database1;User Id=User1;Password=Password1;";
        string connectionString2 = "Server=Server2;Database=Database2;User Id=User2;Password=Password2;";

        SQLHelper sqlHelper1 = new SQLHelper(connectionString1);
        SQLHelper sqlHelper2 = new SQLHelper(connectionString2);

        DataTable result1 = sqlHelper1.ExecuteQuery("SELECT * FROM Table1");
        DataTable result2 = sqlHelper2.ExecuteQuery("SELECT * FROM Table2");

        Console.WriteLine("Result from Database1:");
        result1.Print();

        Console.WriteLine("\nResult from Database2:");
        result2.Print();
    }
}

在這個示例中，我們創建了兩個 SQLHelper 實例，分別使用不同的連接字符串連接到兩個不同的數據庫。然后我們分別執行查詢并打印結果。