problem with c# coding to populate data from mysql table

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i m making a textbox with a button so that when button is clicked it gives sum of specified column in that textbox it has to be done in c#.plz help

C#

MySqlConnection MyCon = new MySqlConnection("server=localhost; Database = nikz; user id=root; password=***; pooling=false;");
MyCon.Open();
MySqlCommand command = new MySqlCommand();
string SQL = "select sum(Actual_amt) from tds";
command.Connection = MyCon;
command.CommandText = SQL;
actamttxtbox.Text = SQL.ExecuteScalar();
command.ExecuteNonQuery();
MyCon.Close();

this is what i hav done and is giving errors

Posted 17-Jul-12 1:05am

nkhldhar

Updated 17-Jul-12 1:10am

StianSandberg

v2

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AmitGajjar 17-Jul-12 7:08am

Whats your problem ? what is your error ?

1 solution

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StianSandberg · Accepted Answer · 2012-07-17T01:12:00

Solution 1

variable SQL is a string. A string has no method ExecuteScalar()

change

C#

actamttxtbox.Text = SQL.ExecuteScalar();

to

C#

actamttxtbox.Text = (string)command.ExecuteScalar();

And you don't need cmd.ExecuteNonQuery();

I've cleaned up a little bit:

C#

MySqlConnection conn = new MySqlConnection("connection-string");
conn.Open();

using(MySqlCommand cmd = new MySqlCommand()){
  cmd.Connection = conn;
  cmd.CommandText = "select sum(Actual_amt) from tds";
  actamttxtbox.Text = cmd.ExecuteScalar().ToString();
}
conn.Close();

Posted 17-Jul-12 1:12am

StianSandberg

Updated 17-Jul-12 1:29am

v6

Comments

nkhldhar 17-Jul-12 7:16am

Cannot implicitly convert type 'object' to 'string'. An explicit conversion exists (are you missing a cast?)

nkhldhar 17-Jul-12 7:17am

edited but having this error

StianSandberg 17-Jul-12 7:17am

You are correct! Fixed it in my last edit :)

nkhldhar 17-Jul-12 7:21am

now this error pops up
The name 'MyCon' does not exist in the current context

StianSandberg 17-Jul-12 7:23am

ops.. sorry. a typo.. fixed it now. Changed your variable name and forgot to update cmd.Connection = conn;.. my bad..

nkhldhar 17-Jul-12 7:24am

and wat do i replace (string) with???do i need to keep brackets on

StianSandberg 17-Jul-12 7:25am

you should be able to run code as is now (after my last edit)

nkhldhar 17-Jul-12 7:26am

do i need to replace (string) with something?

StianSandberg 17-Jul-12 7:27am

no. That is a cast. Because cmd.ExecuteScalar() returns an object, you need to cast that object to a string. The actamttxtbox.Text property expects a string

nkhldhar 17-Jul-12 7:26am

i m having this error now
Unable to cast object of type 'System.Double' to type 'System.String'.

StianSandberg 17-Jul-12 7:28am

ok, it's a double.
try actamttxtbox.Text = cmd.ExecuteScalar().ToString();

nkhldhar 17-Jul-12 7:30am

AAhhhh!!! finallyyy!! thanks buddy :)

StianSandberg 17-Jul-12 7:31am

Please mark my answer as accepted :)