Commenting Code VB Classic, like all the VB-based languages, uses a single quote (') or the original class-style basic "REM" (most developers just use a quote). VB Classic does NOT have a multiple line comment.
Directives - #
Directives are sometimes called compiler or preprocessor directives. A # is used for directives within VB Classic code. VB Classic offers only an #If..then/#ElseIf/#Else directive.
VB Classic is a non-OOP language with some OOP features. It offers both Subs and Functions. A Sub does not return a value while a Function does. When Subs and Functions are used in a class module, they become the methods of the class.
When an object instance is created from a class, VB6 calls a special parameter-less sub named Class_Initialize. Since you cannot specify parameters for this sub, you also cannot overload it.
When a class is destroyed, VB6 calls a special sub called Class_Terminate.
VB6 has limited support for interfaces. You can create an interface of abstract methods and properties and then implement them in one or more descendant classes. It's a single level implementation though (you cannot inherit beyond that). The parent interface class is a pure abstract class (all methods and properites are abstract, you cannot implement any of them in the parent class).
In the single level descendant class, you have to implement all methods and properties and you cannot add any. Your first line of code is Implements InterfaceName.
VB Classic is a loosely typed language. Declaring variables is optional unless you use the Option Explicit statement to force explicit declaration of all variables with Dim, Private, Public, or ReDim. Using Option Explicit is strongly recommended to avoid incorrectly typing an existing variable and to avoid any confusion about variable scope.
Undeclared variables are variants. To specifically declare a variant, use:
Dim x As Variant
Dim x
Common data types include Byte (0..255), Boolean, Integer (2-byte integers), Long (4-byte integers), Currency, Single (32-bit number), Double (64-bit number), Date, String, and variant.
Variables declared with Dim at the module level are available to all procedures within the module. At the procedure level, variables are available only within the procedure.
When an object instance is destroyed, VB6 calls a special parameter-less sub named Class_Terminate. For example, when the variable falls out of scope. Since you cannot specify parameters for this sub, you also cannot overload it.
When an object instance is created from a class, VB6 calls a special sub called Class_Initialize.
In VB Classic, you have to add an empty string to the value being compared in order to get consistent results. For example, add &"" to your string varilable or it's code equivalent &vbNullString. Then compare to an empty string or verify it's length to 0 with Len.
In addition to Add and Item, collections also offer Count and Remove. Notice that Add uses the format of Value, Key (which is backwards from many other languages).
Commenting Code VB Classic, like all the VB-based languages, uses a single quote (') or the original class-style basic "REM" (most developers just use a quote). VB Classic does NOT have a multiple line comment.
Directives - #
Directives are sometimes called compiler or preprocessor directives. A # is used for directives within VB Classic code. VB Classic offers only an #If..then/#ElseIf/#Else directive.
When an object instance is destroyed, VB6 calls a special parameter-less sub named Class_Terminate. For example, when the variable falls out of scope. Since you cannot specify parameters for this sub, you also cannot overload it.
When an object instance is created from a class, VB6 calls a special sub called Class_Initialize.
When an object instance is created from a class, VB6 calls a special parameter-less sub named Class_Initialize. Since you cannot specify parameters for this sub, you also cannot overload it.
When a class is destroyed, VB6 calls a special sub called Class_Terminate.
Crystal Reports was very popular with VB Classic developers and came bundled with Visual Basic 3 through 6. VB6 offers both Crystal Reports and the new Microsoft Data Report Designer.
VB Classic
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