Working with DTO Collections
Collections are objects that contain other objects.
Instantiating a Collection
Visual Basic
Use the Set keyword to set a variable to the collection object.
Dim result as DtoResult
Dim my_session as New DtoSession
Dim my_databases as DtoDatabases
result = my_session.Connect("myserver", "username", "pw")
if not(result=0) Then
’ error handling for Connect method
end if
’ Use Set when an object or collection
’ is the return type
Set my_databases = my_session.Databases
ASP
When using ASP, you normally need to instantiate only two objects directly: DtoSession and DtoDictionary. Instantiating an object with Active Server Pages uses the Create Object syntax on the built-in Server object of IIS.
Set my_session = Server.CreateObject("DTO.DtoSession.2")
Note:
If you want the object to exist between HTTP calls, you must use the IIS built-in object Session to maintain the object’s state, as shown in the following example.
Set Session("my_session") = Server.CreateObject("DTO.DtoSession.2")
However, if you create new objects, such as databases, DSNs, tables, columns, indexes, or segments, you use this same syntax. The progid for each object follows the convention shown in the preceding example.
For other collections, you can use the Set syntax documented previously for Visual Basic.
Looping through a Collection
Visual Basic
There are two ways to loop through collections in Visual Basic: using a For loop and using a counter.
The following shows the Visual Basic syntax to loop through a collection using a For/Next statement.
’ obtain categories collection
Dim my_categories as DtoCategories
Dim category as DtoCategory
Set my_categories = my_session.Categories
’ loop through collection
For Each category In my_categories
settings = category.Settings
Next
The following shows the Visual Basic syntax to loop through a collection using a counter.
Dim column as DtoColumn
Dim table as DtoTable
Set table = dictionary.Tables("Billing")
Dim i as long
for i=1 to table.Columns.count
set column=table.Columns(i)
’perform operations with this column
next i
ASP
Here is sample ASP code that displays a list of categories for PSQL configuration:
<%
Set Session("my_session") = Server.CreateObject("DTO.DtoSession.2")
result = Session("my_session").Connect("myserver", "username", "pw")
’ Error handling for Connect method not shown
Set my_categories = Session("my_session").Categories
’ Now loop through and print categories in a unordered HTML list (<UL></UL>)
%>
<ul>
<% For each category in my_categories %>
<%
’ The = (equal) sign displays the variable
%>
<%
’ in the HTML stream and is a short cut
%>
<%
’ for the Response.Write() built-in
%>
<%
’ VBScript method.
%>
<li><%=cat.CategoryId> - <%=cat.Name%></li>
<% Next %>
</ul>
Obtaining Number of Members
Visual Basic
Use the Count property to determine the number of objects in the collection.
Dim num_items as Integer
Dim my_session as New DtoSession
Dim result as DtoResult
result = my_session.Connect("myserver", "username", "pw")
’ Error handling for Connect method not shown
Set my_databases = my_session.Databases
num_items = my_databases.Count
ASP
Use the Count property to determine the number of objects in the collection.
<%
Set Session("my_session") = Server.CreateObject("DTO.DtoSession.2")
result = Session("my_session").Connect("myserver", "username", "pw")
’ Error handling for Connect method not shown
Set my_databases = Session("my_session").Databases
num_items = my_databases.Count
’ Now write output to HTML stream
Response.Write("<p>Number of databases = " & num_items)
%>
Obtaining a Specific Member
Visual Basic and ASP
Use the Item property to obtain a specific member object of a collection.
Elements within collections can be accessed using their ordinals. Some collections support accessing elements using the element’s unique property, such as name. All ordinals are 1-based.
Since Item is a default property of the collection object, the following two statements are identical:
Collection.Item(index)
Collection(index)
Note: If you want the object to exist between HTTP calls, you must use the IIS built-in object Session to maintain the object’s state, as shown in the following example.