Why did I have to manually set the .value from the .text on losing focus in an unbound textbox - vba

Question

I have an unbound textbox to accept the delete older than: number of days. It is in the report header. I set it to 30 days but I want the user to be able to change it. I was banging my head trying to figure out why entering 40 was not being accepted and it reverted back to 30 every time. I finally decided on using the lost_focus event to set .value to .text. That worked.
Further research showed that when the textbox get's focus text and value are both the same, 30 in my case. Changing the number in the text box to 40 shows the values of text at 40 and value at 30. Unless I specifically set Value to the value of text Access changes text to the value of value. This is different behavior than other places in Access such as forms.
Can anyone tell me why this might be? I can't find any setting that might do this. Is it because it's in a report header? what is the difference between this and every other text box I've ever used?

Answer 1

From a "best practices" viewpoint, Access Reports are not intended to be used interactively despite the ability to manipulate some unbound controls. Although workarounds can be implemented that function sufficiently well, such solutions are often incomplete and buggy and function differently depending on the active view: Report View vs. Print Preview. Appropriate design patterns include using Access Forms for specifying report options which then open the Report in a static configuration.
This may not satisfy the question "Why?" if seeking a deeper answer as to why Microsoft implemented inconsistent binding behavior in Access, or why they allowed interactive controls in reports at all if they don't behave the same way as in forms. But Access has plenty of other quirky behaviors that have no known/published explanation.
Regarding the priority of the Value property updating the Text property (and not vice versa): Value is the key field because it contains the actual data for the control (bound or unbound). Although it is natural to have a single control for both display and input (uh, that's how almost all controls work), the processes of displaying data and parsing user input are two distinct functions. The visual representation returned by the Text property can be manipulated using the various formatting properties, and technically could display an incomplete representation of the underlying Value data. If there are any conflicts between the stored Value property and the Text property, it is natural that the existing Value property has precedent.
My guess is that the automatic binding behavior was "relaxed" for reports to allow more flexible custom reporting output. First consider an Access Form in Datasheet view: An unbound Form control shows the same value for all records. Even if the control is edited while on a particular row, the updated value is displayed for all rows. The same control object is essentially repainted for each row and there is no concept of individual instances of the control that can hold different values. Bound controls have built-in code that repaint the control with data from the particular row, but there are still not multiple instances each "holding" the individual values. The visual output differs from an intuitive object-oriented paradigm where our minds what to assign each visual row its own in-memory instance of the controls--it just doesn't work like that in Access.
Unlike the Form behavior just described, the Report's Print Preview (and actual printed output) allows unbound controls to display different data per row using the Detail_Format() event. Within the Detail_Format() event, one can set the Value property of a control at which time the Text property is automatically updated according to various formatting properties. This update Text is then output for the current row. Perhaps (just guessing) that this behavior would not function properly if the Text property updated the value property. I suspect it would cause recursive events during report generation. Because reports are not meant to be interactive, relevant text-input parsing code was "disconnected" so that it doesn't behave like on a form.
All that explanation doesn't make Access any less frustrating nor remove its limitations, but at least learn to adapt and design things in the "Access-esque" way rather than fighting it.

Answer 2

your best bet is to design a form with the unbound combo boxes and have your data displayed in a subreport. I like to design my reports so that when values are updated the query for the recordsource of the report is generated doing this requires 2 queries to exist, one with all data possible and a filtered one as subreport recordsource. This will control the data for printing and also allow users to close or navigate away from the report and return to the data later.
Private Sub ComboBox1_AfterUpdate()
Dim Query1 as Object
Dim Temp_Name as Variant
Temp_Name = SubReport.SourceObject
SubReport.SourceObject = Empty
Set Query1 = Me.Form.Application.DBEngine.Workspaces(0).Databases(0).QueryDefs ("SubReport_Query")
Query1.SQL = "Select * Unfiltered_Query WHERE Field1 <= " ComboBox1 & ";"
SubReport.SourceObject = Temp_Name
End Sub