This document is a superset of the Visual Basic coding conventions found in the Visual Basic "Programmer's Guide."
NOTE: The third-party controls mentioned in this article are manufactured by vendors independent of Microsoft. Microsoft makes no warranty, implied or otherwise, regarding these controls' performance or reliability.
- standardize the structure, coding style and logic of an application.
- create precise, readable, and unambiguous source code.
- be consistent with other language conventions (most importantly, the Visual Basic Programmers Guide and standard Windows C Hungarian notation).
- be efficient from a string size and labor standpoint, thus allowing a greater opportunity for longer and fuller object names.
- define the minimal requirements necessary to do the above.
Setting Environment OptionsUse Option Explicit. Declare all variables to save programming time by reducing the number of bugs caused by typos (for example, aUserNameTmp vs. sUserNameTmp vs. sUserNameTemp). In the Environment Options dialog, set Require Variable Declaration to Yes. The Option Explicit statement requires you to declare all the variables in your Visual Basic program. Save Files as ASCII Text. Save form (.FRM) and module (.BAS) files as ASCII text to facilitate the use of version control systems and minimize the damage that can be caused by disk corruption. In addition, you can:
- use your own editor
- use automated tools, such as grep
- create code generation or CASE tools for Visual Basic
- perform external analysis of your Visual Basic code
Object Naming Conventions for Standard ObjectsThe following tables define the MCS standard object name prefixes. These prefixes are consistent with those documented in the Visual Basic Programmers Guide.
Prefix Object Type Example
ani Animation button aniMailBox
bed Pen Bedit bedFirstName
cbo Combo box and drop down list box cboEnglish
chk Checkbox chkReadOnly
clp Picture clip clpToolbar
cmd (3d) Command button (3D) cmdOk (cmd3dOk)
com Communications comFax
ctr Control (when specific type unknown) ctrCurrent
dat Data control datBiblio
dir Directory list box dirSource
dlg Common dialog control dlgFileOpen
drv Drive list box drvTarget
fil File list box filSource
frm Form frmEntry
fra (3d) Frame (3d) fraStyle (fra3dStyle)
gau Gauge gauStatus
gpb Group push button gpbChannel
gra Graph graRevenue
grd Grid grdPrices
hed Pen Hedit hedSignature
hsb Horizontal scroll bar hsbVolume
img Image imgIcon
ink Pen Ink inkMap
key Keyboard key status keyCaps
lbl Label lblHelpMessage
lin Line linVertical
lst List box lstPolicyCodes
mdi MDI child form mdiNote
mpm MAPI message mpmSentMessage
mps MAPI session mpsSession
mci MCI mciVideo
mnu Menu mnuFileOpen
opt (3d) Option Button (3d) optRed (opt3dRed)
ole OLE control oleWorksheet
out Outline control outOrgChart
pic Picture picVGA
pnl3d 3d Panel pnl3d
rpt Report control rptQtr1Earnings
shp Shape controls shpCircle
spn Spin control spnPages
txt Text Box txtLastName
tmr Timer tmrAlarm
vsb Vertical scroll bar vsbRate
Object Naming Convention for Database Objects
NOTE: Using a suffix for queries allows each query to be sorted with its associated table in Microsoft Access dialogs (Add Table, List Tables Snapshot).
Prefix Object Type Example
db ODBC Database dbAccounts
ds ODBC Dynaset object dsSalesByRegion
fdc Field collection fdcCustomer
fd Field object fdAddress
ix Index object ixAge
ixc Index collection ixcNewAge
qd QueryDef object qdSalesByRegion
qry (suffix) Query (see NOTE) SalesByRegionQry
ss Snapshot object ssForecast
tb Table object tbCustomer
td TableDef object tdCustomers
Menu Naming ConventionsApplications frequently use an abundance of menu controls. As a result, you need a different set of naming conventions for these controls. Menu control prefixes should be extended beyond the initial mnu label by adding an additional prefix for each level of nesting, with the final menu caption at the end of the name string. For example:
When this convention is used, all members of a particular menu group are listed next to each other in the object drop-down list boxes (in the code window and property window). In addition, the menu control names clearly document the menu items to which they are attached.
Menu Caption Sequence Menu Handler Name
Naming Conventions for Other ControlsFor new controls not listed above, try to come up with a unique three character prefix. However, it is more important to be clear than to stick to three characters.
For derivative controls, such as an enhanced list box, extend the prefixes above so that there is no confusion over which control is really being used. A lower-case abbreviation for the manufacturer would also typically be added to the prefix. For example, a control instance created from the Visual Basic Professional 3D frame could uses a prefix of fra3d to avoid confusion over which control is really being used. A command button from MicroHelp could use cmdm to differentiate it from the standard command button (cmd).
Third-party ControlsEach third-party control used in an application should be listed in the application's overview comment section, providing the prefix used for the control, the full name of the control, and the name of the software vendor:
Prefix Control Type Vendor
cmdm Command Button MicroHelp
Variable and Routine NamingVariable and function names have the following structure: <prefix><body><qualifier><suffix>
Part Description Example
<prefix> Describes the use and scope of the variable. iGetRecordNext
<body> Describes the variable. iGetNameFirst
<qualifier> Denotes a derivative of the variable. iGetNameLast
<suffix> The optional Visual Basic type character. iGetRecordNext%
The following tables define variable and function name prefixes that are based on Hungarian C notation for Windows. These prefixes should be used with all variables and function names. Use of old Basic suffixes (such as %, &, #, etc.) are discouraged.
Variable and Function Name Prefixes:
NOTE: the values in the Converged column represent efforts to pull together the naming standards for Visual Basic, Visual Basic for Applications, and Access Basic. It is likely that these prefixes will become Microsoft standards at some point in the near future.
Prefix Converged Variable Use Data Type Suffix
b bln Boolean Integer %
c cur Currency - 64 bits Currency @
d dbl Double - 64 bit Double #
dt dat Date and Time Variant
e err Error
f sng Float/Single - 32 Single !
h Handle Integer %
i Index Integer %
l lng Long - 32 bit Long &
n int Number/Counter Integer %
s str String String $
u Unsigned - 16 bit Long &
udt User-defined type
vnt vnt Variant Variant
Scope and Usage Prefixes:
Hungarian notation is as valuable in Visual Basic as it is in C. Although the Visual Basic type suffixes do indicate a variable's data type, they do not explain what a variable or function is used for, or how it can be accessed. Here are some examples:
m Local to module or form
st Static variable
(no prefix) Non-static variable, prefix local to procedure
v Variable passed by value (local to a routine)
r Variable passed by reference (local to a routine)
bSend - A Boolean flag defining the success of the last Send operation
hSend - A Handle to the Comm interface
Hungarian notation is also widely used by Windows C programmers and constantly referenced in Microsoft product documentation and in industry programming books. Additionally, the bond between C programmers and programmers who use Visual Basic will become much stronger as the Visual C++ development system gains momentum. This transition will result in many Visual Basic programmers moving to C for the first time and many programmers moving frequently back and forth between both environments.
The Body of Variable and Routine NamesThe body of a variable or routine name should use mixed case and should be as long as necessary to describe its purpose. In addition, function names should begin with a verb, such as InitNameArray or CloseDialog.
For frequently used or long terms, standard abbreviations are recommended to help keep name lengths reasonable. In general, variable names greater than 32 characters can be difficult to read on VGA displays.
When using abbreviations, make sure they are consistent throughout the entire application. Randomly switching between Cnt and Count within a project will lead to unnecessary confusion.
Qualifiers on Variable and Routine NamesRelated variables and routines are often used to manage and manipulate a common object. In these cases, use standard qualifiers to label the derivative variables and routines. Although putting the qualifier after the body of the name might seem a little awkward (as in sGetNameFirst, sGetNameLast instead of sGetFirstName, sGetLastName), this practice will help order these names together in the Visual Basic editor routine lists, making the logic and structure of the application easier to understand. The following table defines common qualifiers and their standard meaning:
Qualifier Description (follows Body)
First First element of a set.
Last Last element of a set.
Next Next element in a set.
Prev Previous element in a set.
Cur Current element in a set.
Min Minimum value in a set.
Max Maximum value in a set.
Save Used to preserve another variable that must be reset later.
Tmp A "scratch" variable whose scope is highly localized within the
code. The value of a Tmp variable is usually only valid across
a set of contiguous statements within a single procedure.
Src Source. Frequently used in comparison and transfer routines.
Dst Destination. Often used in conjunction with Source.
User Defined TypesDeclare user defined types in all caps with _TYPE appended to the end of the symbol name. For example:
sName As String
sState As String * 2
lID as Long
Dim custNew as CUSTOMER_TYPE
Naming ConstantsThe body of constant names should be UPPER_CASE with underscores (_) between words. Although standard Visual Basic constants do not include Hungarian information, prefixes like i, s, g, and m can be very useful in understanding the value and scope of a constant. For constant names, follow the same rules as variables. For Example:
<mnUSER_LIST_MAX ' Max entry limit for User list (integer value,
' local to module)
gsNEW_LINE ' New Line character string (global to entire
Variant Data TypeIf you know that a variable will always store data of a particular type, Visual Basic can handle that data more efficiently if you declare a variable of that type.
However, the variant data type can be extremely useful when working with databases, messages, DDE, or OLE. Many databases allow NULL as a valid value for a field. Your code needs to distinguish between NULL, 0 (zero), and "" (empty string). Many times, these types of operations can use a generic service routine that does not need to know the type of data it receives to process or pass on the data. For example:
Sub ConvertNulls(rvntOrg As Variant, rvntSub As Variant)
' If rvntOrg = Null, replace the Null with rvntSub
If IsNull(rvntOrg) Then rvntOrg = rvntSub
vnt1 = "10.01" : vnt2 = 11 : vnt3 = "11" : vnt4 = "x4"
vntResult = vnt1 + vnt2 ' Does vntResult = 21.01 or 10.0111?
vntResult = vnt2 + vnt1 ' Does vntResult = 21.01 or 1110.01?
vntResult = vnt1 + vnt3 ' Does vntResult = 21.01 or 10.0111?
vntResult = vnt3 + vnt1 ' Does vntResult = 21.01 or 1110.01?
vntResult = vnt2 + vnt4 ' Does vntResult = 11x4 or ERROR?
vntResult = vnt3 + vnt4 ' Does vntResult = 11x4 or ERROR?
iVar1 = 5 + val(sVar2) ' use this (explicit conversion)
vntVar1 = 5 + vntVar2 ' not this (implicit conversion)
Commenting Your CodeAll procedures and functions should begin with a brief comment describing the functional characteristics of the routine (what it does). This description should not describe the implementation details (how it does it) because these often change over time, resulting in unnecessary comment maintenance work, or worse yet, erroneous comments. The code itself and any necessary in-line or local comments will describe the implementation.
Parameters passed to a routine should be described when their functions are not obvious and when the routine expects the parameters to be in a specific range. Function return values and global variables that are changed by the routine (especially through reference parameters) must also be described at the beginning of each routine.
Routine header comment blocks should look like this (see the next section "Formatting Your Code" for an example):
Every non-trivial variable declaration should include an in-line comment describing the use of the variable being declared.
Section Comment Description
Purpose What the routine does (not how).
Inputs Each non-obvious parameter on a separate line with
Assumes List of each non-obvious external variable, control, open file,
and so on.
Returns Explanation of value returned for functions.
Effects List of each effected external variable, control, file, and
so on and the affect it has (only if this is not obvious)
Variables, controls, and routines should be named clearly enough that in- line commenting is only needed for complex or non-intuitive implementation details.
An overview description of the application, enumerating primary data objects, routines, algorithms, dialogs, database and file system dependencies, and so on should be included at the start of the .BAS module that contains the project's Visual Basic generic constant declarations.
NOTE: The Project window inherently describes the list of files in a project, so this overview section only needs to provide information on the most important files and modules, or the files the Project window doesn't list, such as initialization (.INI) or database files.
Formatting Your CodeBecause many programmers still use VGA displays, screen real estate must be conserved as much as possible, while still allowing code formatting to reflect logic structure and nesting.
Standard, tab-based, block nesting indentations should be two to four spaces. More than four spaces is unnecessary and can cause statements to be hidden or accidentally truncated. Less than two spaces does not sufficiently show logic nesting. In the Microsoft Knowledge Base, we use a three-space indent. Use the Environment Options dialog to set the default tab width.
The functional overview comment of a routine should be indented one space. The highest level statements that follow the overview comment should be indented one tab, with each nested block indented an additional tab. For example:
'Purpose: Locate first occurrence of a specified user in UserList array.
'Inputs: rasUserList(): the list of users to be searched
' rsTargetUser: the name of the user to search for
'Returns: the index of the first occurrence of the rsTargetUser
' in the rasUserList array. If target user not found, return -1.
'VB3Line: Enter the following lines as one line
Function iFindUser (rasUserList() As String, rsTargetUser as String) _
Dim i As Integer ' loop counter
Dim bFound As Integer ' target found flag
iFindUser = -1
i = 0
While i <= Ubound(rasUserList) and Not bFound
If rasUserList(i) = rsTargetUser Then
bFound = True
iFindUser = i
OperatorsAlways use an ampersand (&) when concatenating strings, and use the plus sign (+) when working with numerical values. Using a plus sign (+) with non-numerical values, may cause problems when operating on two variants. For example:
vntVar1 = "10.01"
vntVar2 = 11
vntResult = vntVar1 + vntVar2 ' vntResult = 21.01
vntResult = vntVar1 & vntVar2 ' vntResult = 10.0111
ScopeVariables should always be defined with the smallest scope possible. Global variables can create enormously complex state machines and make the logic of an application extremely difficult to understand. Global variables also make the reuse and maintenance of your code much more difficult. Variables in Visual Basic can have the following scope:
In a Visual Basic application, only use global variables when there is no other convenient way to share data between forms. You may want to consider storing information in a control's Tag property, which can be accessed globally using the form.object.property syntax.
Scope Variable Declared In: Visibility
Procedure-level Event procedure, sub, or Visible in the
function procedure in which
it is declared
Form-level, Declarations section of a form Visible in every
Module-level or code module (.FRM, .BAS) procedure in the
form or code
Global Declarations section of a code Always visible
module (.BAS, using Global
If you must use global variables, it is good practice to declare all of them in a single module and group them by function. Give the module a meaningful name that indicates its purpose, such as GLOBAL.BAS.
With the exception of global variables (which should not be passed), procedures and functions should only operate on objects that are passed to them. Global variables that are used in routines should be identified in the general comment area at the beginning of the routine. In addition, pass arguments to subs and functions using ByVal, unless you explicitly want to change the value of the passed argument.
Write modular code whenever possible. For example, if your application displays a dialog box, put all the controls and code required to perform the dialog's task in a single form. This helps to keep the application's code organized into useful components and minimizes its runtime overhead.
Third-party ControlsNOTE: The products discussed below are manufactured by vendors independent of Microsoft. Microsoft makes no warranty, implied or otherwise, regarding these products' performance or reliability.
The following table lists standard third-party vendor name prefix characters to be used with control prefixes:
The following table lists standard third-party control prefixes:
MicroHelp (VBTools) m
Pioneer Software p
Crescent Software c
Sheridan Software s
Other (Misc) o
Control Control Abbr Vendor Example VBX File
Type Name Name
Alarm Alarm almm MicroHelp almmAlarm MHTI200.VBX
Animate Animate anim MicroHelp animAnimate MHTI200.VBX
Callback Callback calm MicroHelp calmCallback MHAD200.VBX
Combo Box DB_Combo cbop Pioneer cbopComboBox QEVBDBF.VBX
Combo Box SSCombo cbos Sheridan cbosComboBox SS3D2.VBX
Check Box DB_Check chkp Pioneer chkpCheckBox QEVBDBF.VBX
Chart Chart chtm MicroHelp chtmChart MHGR200.VBX
Clock Clock clkm MicroHelp clkmClock MHTI200.VBX
Button Command cmdm MicroHelp cmdmCommandButton MHEN200.VBX
Button DB_Command cmdp Pioneer cmdpCommandButton QEVBDBF.VBX
Button (Group) Command cmgm MicroHelp cmgmBtton MHGR200.VBX
Button Command cmim MicroHelp cmimCommandButton MHEN200.VBX
CardDeck CardDeck crdm MicroHelp crdmCard MHGR200.VBX
Dice Dice dicm MicroHelp dicmDice MHGR200.VBX
List Box (Dir) SSDir dirs Sheridan dirsDirList SS3D2.VBX
List Box (Drv) SSDrive drvs Sheridan drvsDriveList SS3D2.VBX
List Box (File) File List film MicroHelp filmFileList MHEN200.VBX
List Box (File) SSFile fils Sheridan filsFileList SS3D2.VBX
Flip Flip flpm MicroHelp flpmButton MHEN200.VBX
Scroll Bar Form Scroll fsrm MicroHelp fsrmFormScroll ???
Gauge Gauge gagm MicroHelp gagmGauge MHGR200.VBX
Graph Graph gpho Other gphoGraph XYGRAPH.VBX
Grid Q_Grid grdp Pioneer grdpGrid QEVBDBF.VBX
Scroll Bar Horizontal hsbm MicroHelp hsbmScroll MHEN200.VBX
Scroll Bar DB_HScroll hsbp Pioneer hsbpScroll QEVBDBF.VBX
Graph Histo hstm MicroHelp hstmHistograph MHGR200.VBX
Invisible Invisible invm MicroHelp invmInvisible MHGR200.VBX
List Box Icon Tag itgm MicroHelp itgmListBox MHAD200.VBX
Key State Key State kstm MicroHelp kstmKeyState MHTI200.VBX
Label Label (3d) lblm MicroHelp lblmLabel MHEN200.VBX
Line Line linm MicroHelp linmLine MHGR200.VBX
List Box DB_List lstp Pioneer lstpListBox QEVBDBF.VBX
List Box SSList lsts Sheridan lstsListBox SS3D2.VBX
MDI Child MDI Control mdcm MicroHelp mdcmMDIChild ???
Menu SSMenu mnus Sheridan mnusMenu SS3D3.VBX
Marque Marque mrqm MicroHelp mrqmMarque MHTI200.VB
Picture OddPic odpm MicroHelp odpmPicture MHGR200.VBX
Picture Picture picm MicroHelp picmPicture MHGR200.VBX
Picture DB_Picture picp Pioneer picpPicture QEVBDBF.VBX
Property Vwr Property pvrm MicroHelp pvrmPropertyViewer MHPR200.VBX
Option (Group) DB_RadioGroup radp Pioneer radqRadioGroup QEVBDBF.VBX
Slider Slider sldm MicroHelp sldmSlider MHGR200.VBX
Button (Spin) Spinner spnm MicroHelp spnmSpinner MHEN200.VBX
Spreadsheet Spreadsheet sprm MicroHelp sprmSpreadsheet MHAD200.VBX
Picture Stretcher strm MicroHelp strmStretcher MHAD200.VBX
Screen Saver Screen Saver svrm MicroHelp svrmSaver MHTI200.VBX
Switcher Switcher swtm MicroHelp swtmSwitcher ???
List Box Tag tagm MicroHelp tagmListBox MHEN200.VBX
Timer Timer tmrm MicroHelp tmrmTimer MHTI200.VBX
ToolBar ToolBar tolm MicroHelp tolmToolBar MHAD200.VBX
List Box Tree trem MicroHelp tremTree MHEN200.VBX
Input Box Input (Text) txtm MicroHelp inpmText MHEN200.VBX
Input Box DB_Text txtp Pioneer txtpText QEVBDBF.VBX
Scroll Bar Vertical vsbm MicroHelp vsbmScroll MHEN200.VBX
Scroll Bar DB_VScroll vsbp Pioneer vsbpScroll QEVBDBF.VBX
ID článku: 110264 - Poslední kontrola: 8. 1. 2003 - Revize: 1