Calling Stored procedure

[thai anh vu]

I've got a problem when calling a stored procedure

HERE IS MY STORED

DELIMITER $$

DROP PROCEDURE IF EXISTS `eiwms`.`fn_Supplier_CreateSupplier`$$
CREATE PROCEDURE `eiwms`.`fn_Supplier_CreateSupplier` (
IN suppName varchar(100), IN suppPhone INT(11),
IN suppAddress varchar(200), IN suppChar varchar(200))
BEGIN
INSERT INTO supplier(Name, SupplierPhone, Address, Characteristic)
VALUES(suppName, suppPhone, suppAddress, suppChar);
END$$

DELIMITER ;

AND THE SEGMENT OF CODE TO CALL STORED PROCEDURE
MySqlCommand cmd = new MySqlCommand("eiwms.fn_Supplier_CreateSupplier", con);
cmd.CommandType = CommandType.StoredProcedure;

cmd.Parameters.Add("suppName", txtName.Text);
cmd.Parameters.Add("suppPhone", int.Parse(txtPhone.Text));
cmd.Parameters.Add("suppAddress", txtAddress.Text);
cmd.Parameters.Add("suppChar", txtChar.Text);

con.Open();
cmd.ExecuteNonQuery();

THE FOLLOWING ERROR ALWAYS APPEARS WHEN I EXECUTE THE STORED:
Invalid attempt to access a field before calling Read().

I don't know how to fix it.
I need you help.
Thanks a lot