How to add database query results to an array - arrays

Question

I am trying to select string values from an Access database and then place them into an array of strings so that I can perform a loop statement on the array.
However I don't know how to place the result of the query into an array. I know how to query the database but all I need is how to put the result in an array.
My select statement is Select motonum from moto. I want to put motonum in an array.
The whole code to read the data is:
connect2()
If Not cnn2.State = ConnectionState.Open Then
'open connection
cnn2.Open()
'MessageBox.Show("chk2")
End If
cmd5.Connection = cnn2
cmd5.CommandText = "Select motonum from moto"
myData5 = cmd5.ExecuteReader
While myData5.Read
'code to return results here
End While`

Answer 1

There are any number of different ways to approach this, depending on the actual needs of your project. First and foremost, I would ask if you actually require a string array as the return type. For most cases, an array is less useful that a List(Of String) or other types which implement IEnumerable.
Here are two options, both of which involve a List(Of String). However, one returns the List to the caller, which can then choose to employ the many useful methods of the List type in working with the data:
THIS is the way I would recommend:
Public Function getListOfMotonum() As List(Of String)
Dim SQL As String = "SELECT motonum FROM moto"
Dim output As New List(Of String)()
' Set the connection string in the Solutions Explorer/Properties/Settings object (double-click)
Using cn = New SqlConnection(Properties.Settings.[Default].MyConnectionString)
Using cmd = New SqlCommand(SQL, cn)
cn.Open()
Try
Dim dr = cmd.ExecuteReader()
While dr.Read()
output.Add(dr("motonum").ToString())
End While
Catch e As SqlException
' Do some logging or something.
MessageBox.Show("There was an error accessing your data. DETAIL: " & e.ToString())
End Try
End Using
End Using
Return output
End Function
Here is a trivial example of code which consumes the output of this function:
Private Sub PrintListToConsole()
Dim MyMotonumList = Me.getListOfMotonum()
For Each item As String In MyMotonumList
Console.WriteLine(item)
Next
End Sub
If your project REQUIRES a string array, the approach may vary. You can return a string from the same function with a couple minor modifications:
' Change the return type in the function signature:
Public Function getArrayOfMotonum() As String()
Dim SQL As String = "SELECT motonum FROM moto"
Dim output As New List(Of String)()
' . . . Same Data Access code as above:
' Just use the .ToArray method of the List class HERE:
Return output.ToArray()
End Function
Or, you can use the same method in your client code, consuming the original function which returns a list:
Private Sub PrintArrayToConsole()
Dim MyMotonumArray = Me.getArrayOfMotonum()
For Each item As String In MyMotonumArray
Console.WriteLine(item)
Next
End Sub
Returning the List from your function provides a more flexible return type, with many useful methods.
As a side note, allow me to recommend the Using block when consuming data access resources. This handles the proper tear down and disposal of the Connection and Command objects for you.