Error passing parameter to Sqlcommand by parameterizing table

Question

I’m trying to pass parameter in mine select and this bursting the exception:

It is necessary to declare the table variable "@p_tabela".

using (SqlConnection conn = new SqlConnection(connectionString)
{
    try
    {
        conn.Open();
        var sql = "SELECT Id FROM @p_tabela";
        SqlCommand command = new SqlCommand(sql, conn);

        command.Parameters.Add(new SqlParameter("@p_tabela", tabela));

        using (SqlDataReader reader = command.ExecuteReader()) // Estoura erro aqui
        {
            if (reader.Read())
            {
                return true;
            }
        }

        return false;
    }
    catch (Exception ex)
    {
        Console.WriteLine(ex.Message);
    }
    finally
    {
        conn.Close();
    }
}

I’ve tried this too:

• command.Parameters.AddWithValue("@p_tabela", tabela);

• SqlCommand command = new SqlCommand(command, conn); command.Parameters.Add("@p_tabela", SqlDbType.VarChar); command.Parameters["@p_tabela"].Value = tabela;

Second try use from here: https://docs.microsoft.com/pt-br/dotnet/api/system.data.sqlclient.sqlcommand.parameters?view=netframework-4.8 Error image:

Answer 1

The interpolation system SqlCommand only allows using variables in certain locations, the table name is not an allowed location. So the way would be to do with normal interpolation. But remember this is dangerous in many cases, if the data comes from outside make sure you are very good at it, otherwise you will do wrong things and have safety holes. It would be something like that:

$"SELECT Id FROM {tabela}"

I put in the Github for future reference.

Do not forget the comment above, there is a lot wrong with this code (even because you can see that you do not understand why you are doing certain things, this is dangerous), even if it works.