Fill: SelectCommand.Connection error on derived iDBCommand

Question

Before you dowonvote this, please have a look first. I know there numerous threads here with this errormessage, but I haven't found one with this particular problem. I've created a custom command class implementing the IDbCommand interface like this:

internal class Prozedur : IDbCommand
    {
        private static SqlCommand command = new SqlCommand() ;
        private SqlConnection connection;
        string commandtext;
        CommandType commandType;

        public Prozedur(string abfrage)
        {
            commandtext = abfrage;

            commandType = CommandType.StoredProcedure;
            connection = (SqlConnection)new Verbindung();
            SqlCommand command = new SqlCommand(commandtext, connection);

        }

        public static explicit operator SqlCommand(Prozedur v)
        {
            return command;
        }
    ...

I'am using the object like this:

    internal class Tabelle : DataTable
    {
        DataTable tabelle = new DataTable();

        internal Tabelle(string abfrage)
        {
            Prozedur p = new Prozedur(abfrage);

            SqlDataAdapter adapter = new SqlDataAdapter((SqlCommand)p);
            adapter.Fill(tabelle);
        }
    }

However, on the adapter.Fill(tabelle) i get the Error “Fill: SelectCommand.Connection property has not been initialized.”. But if i look at the object p, the connection is there:

Update

If i change the code like this

    internal class Tabelle : DataTable
    {
        DataTable tabelle = new DataTable();

        internal Tabelle(string abfrage)
        {
            Prozedur p = new Prozedur(abfrage);
            SqlCommand c = (SqlCommand)p;
            //added this line
            c.Connection = p.Connection;

            SqlDataAdapter adapter = new SqlDataAdapter((SqlCommand)p);

            adapter.Fill(tabelle);
        }
    }

I get a compiler error for p.Connection; C# Cannot implicitly convert type to. An explicit conversion exists (are you missing a cast?).

The code for the connection is this:

        public IDbConnection Connection
        {
            get
            {

                return connection;
            }

            set
            {
                connection = (SqlConnection)value;
            }
        }

Answer 1

The problem was in the convert method. When I change the code as below it works. Basically I had to make all variables static and return a new SqlCommandObject in the convert method.

 internal class Prozedur : IDbCommand
    {
        private static SqlCommand command = new SqlCommand();
        private static SqlConnection connection;
        static string commandtext;
        CommandType commandType;

        public Prozedur(string abfrage)
        {
            commandtext = abfrage;
            commandType = CommandType.StoredProcedure;
            connection = (SqlConnection)new Verbindung();
        }

        public static explicit operator SqlCommand(Prozedur v)
        {
            return new SqlCommand() { CommandText = commandtext, Connection = connection, CommandType = command.CommandType };
        }
...

And it works like this without static variables:

    internal class Prozedur : IDbCommand
    {
        private SqlCommand command = new SqlCommand();
        private SqlConnection connection;
        string commandtext;
        CommandType commandType;

        public Prozedur(string abfrage)
        {
            commandtext = abfrage;
            commandType = CommandType.StoredProcedure;
            connection = (SqlConnection)new Verbindung();
        }

        public static explicit operator SqlCommand(Prozedur v)
        {
            return new SqlCommand() { CommandText = v.CommandText, Connection = (SqlConnection)v.Connection, CommandType = v.CommandType };
        }
...