MySqlDataAdapter SelectCommand Statement - mysql

Question

I have the following functional code:
Call ConnSettings()
Dim objDs As New DataSet
Dim Query As String
Query = "the query"
Cmd = New MySqlCommand(Query, MysqlConn)
Dim dAdapter As New MySqlDataAdapter
dAdapter.SelectCommand = Cmd
''Dim dAdapter As New MySqlDataAdapter(Query, MysqlConn)
Try
MysqlConn.Open()
dAdapter.Fill(objDs)
MysqlConn.Close()
Catch ex As Exception
MessageBox.Show(ex.Message)
Finally
MysqlConn.Dispose()
End Try
I have noticed that the code is equally functional if I also use
Dim dAdapter As New MySqlDataAdapter(Query, MysqlConn)
instead of:
Cmd = New MySqlCommand(Query, MysqlConn)
Dim dAdapter As New MySqlDataAdapter
dAdapter.SelectCommand = Cmd
Obviously, I would like to use a single line instead of three. However, I am fairly new to VB and would like to know if there are any issues with doing that.

Answer 1

Let's try to improve your code....
First ConnSettings doesn't initialize a global connection variable but a local one and returns it
Public Function ConnSettings() As MySqlConnection
Dim conn As MySqlConnection
conn = new MySqlConnection(yourConnectionStringHere)
conn.Open()
return conn
End Function
Now the code that needs a MySqlConnection could call this ConnSettings and put the return value in a Using Statement
objDS = new DataSet()
Try
Using conn = ConnSettings()
Using dAdapter = New MySqlDataAdapter(theQuery, conn)
dAdapter.Fill(objDs)
End Using
End Using
Catch(ex as Exception
MessageBox.Show(ex.Message)
End Try
This code puts the connection returned in a Using Statement. When the code flows out of the Using Statement the connection is closed and disposed (same for the MySqlDataAdapter) As you can see there is no need for the Finally clause and the Try/Catch block is present just because you want to give an error message to your user (while this is a common practice there is no really sense to put your user in the unconfortable position to try to understand these technically dense messages, better use a log file and advise your user to send the log to you)
In this context also the code inside the ConnSettings is a bit useless. What you really need is just the connectionstring and you could write the creation of the MySqlConnection directly in the calling code.