How to create a DLL file in ASP.NET 4.0?

Please tell me how to create a DLL file in asp.net 4.0

This is my code. Please tell me if there is any problem with this code.

namespace databaselogic
{


public class mycomponent
{
public DataSet getdata(string sql1)
{
SqlConnection con = new SqlConnection("datasource=.\\sqlexpress;attachdbfile=e:\\aspnet\\databaselogic2\\app_data\\peers.mdf;integrated security=true;user instance=true");
SqlDataAdapter da = new SqlDataAdapter(sql1, con);
DataSet ds=new DataSet ();
da.Fill (ds,"d");
return (ds);
}
}
}