填充：SelectCommand.Connection属性尚未初始化

Question

After a while using the website, loading contents, etc.. this message shows "Fill: SelectCommand.Connection property has not been initialized"! I think this is because the sql connection, but not sure... I'd like to know what can i do to prevent this, every time this happens i have to upload a file (SQL class, that make the connection) and the website starts to work again.

My SQL connection:

public class SQL
{

    SqlCommand comandos;
    public SqlConnection sql()
    {
        string Server = @"server"; 
        string Username = "user"; 
        string Password = "pass"; 
        string Database = "database";
        string ConnectionString = "Data Source=" + Server + ";";
        ConnectionString += "User ID=" + Username + ";";
        ConnectionString += "Password=" + Password + ";";
        ConnectionString += "Initial Catalog=" + Database;

        SqlConnection Connection = new SqlConnection();
        try
        {
            Connection.ConnectionString = ConnectionString;
            Connection.Open();
            return Connection;
        }
        catch (Exception)
        {
            if (Connection != null)
            {
                Connection.Dispose();
        }
        return null;
        }
    }

    public void FazerComando(string comando)
    {
        comandos = new SqlCommand(comando, sql());
        comandos.ExecuteNonQuery();
    }

    public DataTable Execute(string comando)
    {
        SqlDataAdapter SQLDataAdapter = new SqlDataAdapter(comando, sql());
        DataTable dtResult = new DataTable();
        SQLDataAdapter.Fill(dtResult);
        return dtResult;
    }
}

Answer 1

This might be related to your problem, but in any case, it's something that should be addressed: You're not disposing your connections when you're done with them. You should use using :

    public void FazerComando(string comando)
    {
        using (var conn = sql())
        {
            comandos = new SqlCommand(comando, conn);
            comandos.ExecuteNonQuery();
        }
    }
    public DataTable Execute(string comando)
    {
        using (var conn = sql())
        {
            SqlDataAdapter SQLDataAdapter = new SqlDataAdapter(comando, conn);
            DataTable dtResult = new DataTable();
            SQLDataAdapter.Fill(dtResult);
            return dtResult;
        }
    }

Answer 2

I've never taken that approach before. We usually just use the connection string in web config, expecially with linq, it works very well. I suggest you have a look at http://blogs.msdn.com/b/visualstudio/archive/2012/06/11/world-of-samples-at-your-fingertips.aspx and follow the trail. You should find a good example of a recommended best practice for connections. The connection string will then be read at the first lauch of your app, and connection pooling (v imortant) used to best effect.

Oh and you are not disposing of your connection, which will cause a memory leek and iis to clear out your app pool when the memeory usage becomes too large -- all v bad

As the other respondant says whilst I was looking up the baet prac link...

HTH