The problem is that you don't use an existing instance of a
method, but a new, empty one:
MailClient MailClient = new MailClient();
public void MailDataSqlInsertion()
String CmdText = "insert into dbo.MailTable_Data(Name,Course,Email,Phone,CompleteMail) Values('" + MailClient.Name + "','" + MailClient.Course + "','" + MailClient.Email + "','" + MailClient.phone + "','" +
You new to not create ne winstance here, but use the one that is passed to you.
There are two ways to do this:
1) Make the
instance a parameter to the
method, so you have to pass the data each time you use it.
2) Make the
class constructor require a
parameter and save it for when it's needed later.
The first option is the most flexible, as you can reuse the
instance for several messages in succession.
But whatever you do, don't do database work like that! Never concatenate strings to build a SQL command. It leaves you wide open to accidental or deliberate SQL Injection attack which can destroy your entire database. Use Parametrized queries instead.
When you concatenate strings, you cause problems because SQL receives commands like:
SELECT * FROM MyTable WHERE StreetAddress = 'Baker's Wood'
The quote the user added terminates the string as far as SQL is concerned and you get problems. But it could be worse. If I come along and type this instead: "x';DROP TABLE MyTable;--" Then SQL receives a very different command:
SELECT * FROM MyTable WHERE StreetAddress = 'x';DROP TABLE MyTable;
Which SQL sees as three separate commands:
SELECT * FROM MyTable WHERE StreetAddress = 'x';
A perfectly valid SELECT
DROP TABLE MyTable;
A perfectly valid "delete the table" command
And everything else is a comment.
So it does: selects any matching rows, deletes the table from the DB, and ignores anything else.
So ALWAYS use parameterized queries! Or be prepared to restore your DB from backup frequently. You do take backups regularly, don't you?