no equiv.

instance var.

App global

variables can be public, private or protected

constants

Mask also lets you mimic m/f app behaviour and automatically move to the next field when this field is full (see AutoTab property). There is no equiv. to AutoTab on textbox.

DAOs will perform faster than Data Controls (can consolidate App into single DB login/connect) but they are still slow accessing non-MS Access type databases (e.g. Oracle, SQL Server) – VB suggests using Remote Data Objects (RDO) in the Enterprise Edition to get a faster interface to these "other" DBs.

DAOs don't automatically move data to/from controls on the Form. All this is now manual. Also appears that if DAO is used (at exclusion of Data Controls), then any listboxes and comboboxes would have to be manually loaded. In other words, runtime and development efficiency is a real tradeoff.

PowerBuilder has native interface to many DBs (don't have to change underlying DWs).

(de)Activate

//, /*…*/ -com't

+ -for concat.

Steps to add combo box into "main table" (where combo box is sourced from "Code Table" and shows Code Table descriptions in the dropdowns):

a) add initial main table data control and non-combo box field controls, as normal
b) add "code table" Data Control to Form (tying its RecordSource to code table in DB)
Add DB combo box to Form and do the following to its properties:
c) set its RowSource property to "code table" data control
d) set its ListField property to code desc
e) set its DataSource property to "main table" Data Control (i.e. where to make updates)
f) set its DataField property to "main table" code id (i.e. where to make updates)
g) set its BoundColumn property to the join field (i.e. the code id)

When Other Fields in Record are from Data Access Object:

- same steps as above, except skip step e, f. Also, step a) involves setting up DAO instead of Data Control (see DAO How-To section).

Note: on the combo box, use right-mouse/properties and choose "drop down list" and "extended matching" so that the user can type in the code (using chars entered, this does a multi-char match while "basic matching" does just uses first char to position & move in list). The default of "combo box" and "basic matching" forces the user to enter the code id, if they want to type in the field (i.e. when not using dropdown).

Note 2: ".Text" property for dbcombo box is current "ListField" value (i.e. typically code desc) while ".BoundText" is current "BoundColumn" value (i.e. typically code id).

To Dynamically Invoke an OLE Object on a Form (and run commands):
MS EXCEL Example

Dim x1 as Object 'declare this at Form level
Set x1 = CreateObject("Excel.Application")
… various object-specific commands … (see VB Sample Code)

If object is not closed in code, user can then "take over" to save, print, etc.

To Add an OLE Control onto a Form:

a) Put OLE onto Form
b) Insert object (specify type)
c) Choose type of link: "Linked" (to save by OLE-object) or "Embedded" (to save inside VB)
d) Specify if drag & drop allowed (e.g. to drop items like bitmaps into OLE object).

To use the OLE control, the user seems to have to right-mouse edit to get simple editing abilities or right-mouse open to open/save documents within the tool.

Chief problem with the Form produced is that all controls get meaningless default names. To change the data control name to a meaningful one (not Data1) entails fixing code for the default buttons, the fields, etc. You also have to change the DataSource for all text controls (to refer to meaningfully named DataControl).

In brief, here is how to setup a window that maintains one row at a time, using DAO:

1. Connect to DB, probably as App starts
Set db = OpenDatabase("Home_vb_DB.mdb")

2. Setup RecordSet (e.g. tablename or SQL Select or query), usually in form load

Set rs = db.OpenRecordset("Person_1")

3. Position to start of recordset, probably in Form load
rs.MoveFirst
f_SetFields <-- write this to move fields from recordset to Form Controls

4. Write f_SetFields (from rs), f_GetFields (to rs), f_ClearFields to manually move data between recordset and Form fields – see sample code.

5. Write button code (Add, Update, Delete) – see sample code.

6. Code MoveNext, MovePrevious, MoveFirst, MoveLast buttons – see sample code.

2. Write VB code (probably generally in Form Load or Search button)
- declare QueryDef variable and then assigning to query
Q = db.QueryDefs("QueryName")

- assign parameters to the query -- assignment, no set.
Q.Parameters("LastName") = sLName

- Finally, assign the recordset to the Query OpenRecordSet
Set rs = Q.OpenRecordset

Note: you can't provide the name of the parameterized query to the Data Control Record Source in design (it won't even show up in RecordSource dropdown). In other words, you'll have to "fake out" a record source that retrieves, at least, the fields that you need to design time – usually the fields that correspond to bound controls (you might get these fields in RecordSource in design by selecting the whole table or, if it's big, creating a query that will intentionally return nothing using a restrictive Where Clause: e.g. Where 1=2).

2. assign sql to a variable: mysql = Select * from bob (or Insert xx into Bob)

3. To execute "action" query: db.execute mysql (e.g. Insert, Update, Delete) to indicate how many record affected (for action query), use db.RecordsAffected.

4. To execute "non-action" query (Select): set rs=db.OpenRecordset(mysql, dbOpenDynaset)

To check data returned from SQL, do rs.MoveFirst, rs.MoveNext to move to needed row(s) and use: rs("desc") to get particular columns from recordset.

dc_x.RecordSource = "Select a, b, from T where c =" & pnum à Number

dc_x.RecordSource = "Select a, b, from T where d =' " & pchar & " ' " à char

- In GetFocus, set IFlag = 0
- In Change, set IFlag = 1
- In LostFocus, "IF IFlag = 1 THEN … code for when item is changed.

** it appears that you've already lost focus by the time this event fires so you have to set focus back to get the user to fix it. Use a global like "validation-in-progress" to ensure you don't get infinite loops resetting focus. See code sample.

2. Row/Col: fires when moving into a new cell (but not when selecting a row). The "current row/column" are the row/col just clicked.

3. SelChange: fires when a row (or column) has been selected for a grid (i.e. selected at the "side"). The "current row" is the row just selected.

2. To look at variables (or expressions):
a) find debug window (a small pop-up) and type "Print sText" (i.e. where sText is the variable of interest). To redo an earlier Print, put cursor in that line, hit Enter.

b) choose "Tool-Add Watch" and enter a variable-name to watch. If debug window is large enough, you can see the value of that variable (or expression) as you hit breakpoints or step through code.

3. Stepping: "Step Into" button steps to next line and into a procedure, if a procedure is being called. "Step Over" button steps to the next line treating a procedure call as a single line.

4. Skipping Over/Back: Put cursor on line you want executed next and choose Run-Set Next Statement. That line will be executed next.

Which Error routine is invoked? If there was an "On Error" in the current proc, that one is executed. Otherwise, it goes back up the calling chain to execute the nearest parents' "On Error" (if any).

The Err object has properties to diagnose the error (it contains last found error, until it is explicitly reset).

In error handling, you might check for a situation or two that you can anticipate (and that the user might take corrective action to fix) and then have a "Case Else" to simply log the error and then do some sort of nice application shutdown.

Alternatively, you can set "On Error Resume Next" to basically ignore error but then explicitly check Err object (as part of your regular code flow) on the next line.

a) Get into Crystal reports from VB add-in menu. (ignore spurious errors that Crystal reports mentions for queries).
b) choose File-New to create a new report, then select report style.
c) after choosing DB, drag-and-drop fields (from a table) in DB field pop-up to the report form (use right mouse to change fonts/formats for fields on report).
d) do print preview to see if report seems correct. If so, save it with ".rpt" extension.

Tie Report into VB App

a) go to tools-custom controls and pick Crystal reports. Then from toolbar, select Crystal reports and place it on the Form.
b) use right-mouse, properties to select the report for the control
c) you can setup a command button (or menu item) to invoke report, with code like:

'dynamically tie to report
crEmployee.ReportFileName = "c:\vb\empl.rpt"

'direct to printer (0 for preview, 2 to save to file)
crEmployee.Destination = 1

'sends report to destination
iResult = crEmployee.PrintReport
If iResult = …

Multi-Table Report

a) go to Crystal report DB menu and define links between tables (if links not already defined in DB itself)
b) now create report by selecting fields from either table.