I want to develop generalized application which can works with all type of databases (Oracle, MySQL, SQLite). So I have provide different data source to the each form from one common place. 

And I also want to use parametrized query who can accept multiple parameters. I am unable to to pass multiple parameters using DbParameter, it works fine with single parameter query but 
not with many. 

So please help me...

```
            dbconnect dc = new dbconnect();//class which contain data source name
            DbConnection con;
            DbCommand cmd;
            DbDataReader dr;
            DbProviderFactory df;
            DataAdapter da;

            df = DbProviderFactories.GetFactory(dbconnect.dbprovider);
            con = df.CreateConnection();
            con.ConnectionString = dbconnect.sqlstr;
            con.Open();
            cmd = df.CreateCommand();
            cmd.CommandText = "update customer set" + " name='@name'," + "address='@address'," + "phone='@phone' " + "where code='@code';";
            cmd.Connection = con;
            DbDataAdapter daa = df.CreateDataAdapter();
            daa.UpdateCommand = cmd;

            DbParameter param = df.CreateParameter();

            param.ParameterName = "@name";
            param.Value = txtname.Text;

            param.ParameterName = "@address";
            param.Value = txtadd.Text;

            param.ParameterName = "@phone";
            param.Value = txtphone.Text;

            param.ParameterName = "@code";
            param.Value = txtcode.Text;
            daa.UpdateCommand.Parameters.Add(param);
            daa.UpdateCommand.ExecuteNonQuery();

            **But this not working.** 

```