Brinkster Articles, All About Variables Part 3: Checking for Specific SubTypes

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All About Variables Part 3 : Checking for specific SubTypes
[Part 1 | Part 2 | Part 3]

There are six different functions that will assist you in determining if a particular variable is one Subtype or another. Below I have listed all of the SubType checking functions:

IsArray(VariableToCheck)
IsDate(VariableToCheck)
IsEmpty(VariableToCheck)
IsNull(VariableToCheck)
IsNumeric(VariableToCheck)
IsObject(VariableToCheck)

All of the above functions return a boolean value (true or false). Some of the above are self explanatory, however a few are not as clear. I will go over the ones that need explaining:

IsEmpty(VariableToCheck)
     What makes a variable empty? If the variable has been created, but has not been assigned a value yet it is considered to be empty. This is different from a value that is empty ("") or equal to NULL.

IsNull(VariableToCheck)
     What makes a variable null? A variable is null only when it equals null. You can set a variable equal to null.

IsNumeric(VariableToCheck)
This will return true if the variable can be converted to a numeric SubType without generating an error.

Example:

myVar = "Hello"
If IsNumeric(myVar) Then
     Response.Write("Variable is numeric.")
Else      Response.Write("Variable is NOT numeric.")
End If

Result:
Variable is NOT numeric.

Another way to determine the variable SubType is the VarType() function.

Syntax:
VarType(VariableToCheck)

The above function will return a number representing the various subtypes. I have listed them for you below:

Subtypes	Value	Description
vbEmpty	0	Not assigned a value
vbNull	1	No matching SubType
vbInteger	2	Integer
vbLong	3	Long
vbSingle	4	Single
vbDouble	5	Double
vbCurrency	6	Currency
vbDate	7	Date
vbString	8	String
vbObject	9	Object
vbError	10	Error
vbBoolean	11	Boolean (true or false)
vbVariant	12	Variant, array of variants only
vbDataObject	13	Data Access
vbDecimal	14	Decimal
vbByte	17	Byte
vbArray	8192	Array

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