为什么在方法的返回类型上获得此不一致的可访问性错误？

Question

I am working on a .NET project. In a DAO class (using ADO.NET but this is not important) I have a method like this:

public static List<Inoltro> GetListaInoltriUltimiGiorni(int IdUor, string Protocollista, int NumeroGiorni, DBConnection config)
{
    string query = PROT_INOLTRO.INOLTRI_ULTIMI_N_GIORNI_BY_UOR_AND_PROTOCOLLISTA;

    List<Inoltro> result = new List<Inoltro>();

    using (SqlConnection con = ArxeiaConnection.getARXEIAStringConnection(config.Tenant + "_" + config.Database))
    {
        using (SqlCommand cmd = new SqlCommand(query, con))
        {
            try
            {
                cmd.Parameters.AddWithValue("@IdUor", IdUor);
                cmd.Parameters.AddWithValue("@Protocollista", Protocollista);
                cmd.Parameters.AddWithValue("@NumeroGiorni", NumeroGiorni);

                con.Open();

                using (SqlDataReader reader = cmd.ExecuteReader())
                {
                    if (reader.HasRows)
                    {
                        // Read advances to the next row.
                        while (reader.Read())
                        {
                            .........................................
                            .........................................
                            .........................................
                        }
                    }
                }
            }
            catch (Exception ex)
            {
                con.Close();
                throw ex;
            }
        }
    }

    return result;
}

As you can see I am creating and returning this object:

List<Inoltro> result = new List<Inoltro>();

The problem is that Visual studio give me the following error on this method signature:

Inconsistent accessibility: return type List<Inoltro> is less accessible than method MyClass.GetListaInoltriUltimiGiorni(....)

Why? What am I missing? How can I fix it?

Answer 1

Your method is public but Inoltro is internal . You cannot have a public method that exposes an internal type. Either make the method internal or the type public .

While we are looking at your code, a few things come to mind.

First, the try catch is unnecessary, since the using already does a Close on the connection if an exception is thrown. Eliminate the try catch .

Second, for your future reference, never say throw ex; in a catch . Say throw; to re-throw an exception. The difference is subtle. throw; re-throws the exact exception that was caught. throw ex; re-throws the exception but resets the stack trace to the current trace, not the original trace.

The only time you want to do throw ex; is when you deliberately want to obscure where an exception came from, for instance, because there is a trust boundary between the current code and the caller. However, in that case it would be better still to throw a new, generic exception.

Third, I don't understand why you have both a while and an if to check to see if the set has rows. Surely if the set is empty then the Read will return false, so there was never a need for the if , right?

Fourth, this is just a style point; normally we would format

using (SqlConnection con = ArxeiaConnection.getARXEIAStringConnection(config.Tenant + "_" + config.Database))
{
    using (SqlCommand cmd = new SqlCommand(query, con))
    {

as

using (SqlConnection con = ArxeiaConnection.getARXEIAStringConnection(config.Tenant + "_" + config.Database))
using (SqlCommand cmd = new SqlCommand(query, con))
{

It is common to have a using whose body is only another using , and in that scenario the unnecessary braces and indentation do not make the code easier to understand.