Invali attempt to call metadata when reader is closed c# winform -

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this edited code removed try catch see getting exceptions. alse marked edited code. code getting on nerves have been googling problem , tried found. checked every connection other code there seems no problem them. each , every connection closed.

    querystring = "select * product prd_code = @c or prd_name=@pn ";     sqlcommand command = new sqlcommand(querystring, con);     command.parameters.addwithvalue("@c", convert.toint32(txtpcode.text));     command.parameters.addwithvalue("@pn", txtpname.text.tostring());     con.open();     //edited here     using (sqldatareader dr = command.executereader())     {     // , here     if (dr != null && fr.hasrows && dr.read() == true)     {         if (txtpcode.text == "")         {             txtpcode.text = dr["prd_code"].tostring();         }         else if (txtpname.text == "")         {             txtpname.text = dr["prd_name"].tostring();         }                     txtpcompany.text = dr["prd_company"].tostring();         txtunitprice.text = dr["prd_price"].tostring();         txtdiscount.text = dr["prd_dis"].tostring();         txtfinalrate.text = dr["prd_final"].tostring();         }          else         {             messagebox.show("no such record exists");              if (txtpname.text == "")             {                 txtpcode.text = "";             }             else if (txtpcode.text == "")             {                  txtpname.text = "";             }             con.close();         }      }     }        

  using (var reader = command.executereader())       {            if (reader.hasrows)               {                  if(reader.read())                  {                     if (txtpcode.text == "")                    {                        txtpcode.text = dr["prd_code"].tostring();                    }                    else if (txtpname.text == "")                    {                        txtpname.text = dr["prd_name"].tostring();                    }                    txtpcompany.text = dr["prd_company"].tostring();                    txtunitprice.text = dr["prd_price"].tostring();                    txtdiscount.text = dr["prd_dis"].tostring();                    txtfinalrate.text = dr["prd_final"].tostring();                 }             }       }

have @ what c# using block , why should use it?


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