xamarin iOS system.data.sqlclient打开方法不起作用

Question

我正在尝试连接到我为Xamarin iOS应用设置的SQL服务器，我遵循了一些指南，建议使用system.data.sqlclient。 当我运行代码时，open方法会弹出this error

这是我编写的用于连接数据库的类（敏感数据已被替换）：

class clsDBConnector
{

    SqlConnectionStringBuilder builder = new SqlConnectionStringBuilder();
    SqlConnection connection = new SqlConnection();
    public clsDBConnector()
    {
        builder.DataSource = "my_server";
        builder.UserID = "my_userid";
        builder.Password = "my_password";
        builder.InitialCatalog = "my_db";
        connection.ConnectionString = builder.ConnectionString;
    }

    public void Connect()
    {
        connection.Open();
    }
    public void Close()
    {
        connection.Close();
    }

    public SqlDataReader Query(string sql)
    {
        SqlCommand command = new SqlCommand(sql, connection);
        return command.ExecuteReader();
    }
}

这是我在视图控制器中创建的用于使用它的功能：

public void displayData(ref List<string> test)
    {
        clsDBConnector dbConnector = new clsDBConnector();
        SqlDataReader dr;
        string sqlStr;
        dbConnector.Connect();
        sqlStr = "SELECT testName FROM dbo.tblTest";
        dr = dbConnector.Query(sqlStr);
        while (dr.Read())
        {
            test.Add(dr[0].ToString());
        }
    {