IsNull Function

Description

Returns a value that indicates whether an expression contains no valid data (Null).

Syntax

IsNull(expression)

The expression named argument can be any numeric or string expression.

Remarks

IsNull returns True if expression is Null, that is, it contains no valid data; otherwise, IsNull returns False. If expression consists of more than one variable, Null in any variable causes True to be returned for the entire expression.

The Null value indicates that the Variant contains no valid data. Null is not the same as Empty, which indicates that a variable has not yet been initialized. It is also not the same as a zero-length string, which is sometimes referred to as a null string.

Important

Use the IsNull function to determine whether an expression contains a Null value. Expressions that you might expect to evaluate True under some circumstances, such as If Var = Null and If Var <> Null, are always False. This is because any expression containing a Null is itself Null and therefore False.

See Also

IsArray Function, IsDate Function, IsEmpty Function, IsError Function, IsMissing Function, IsNumeric Function, IsObject Function, TypeName Function, Variant Data Type, VarType Function.

Example

This example uses the IsNull function to determine if a variable contains a Null.

MyCheck = IsNull(MyVar)    ' Returns False.
MyVar = ""
MyCheck = IsNull(MyVar)    ' Returns False.
MyVar = Null
MyCheck = IsNull(MyVar)    ' Returns True.

This example creates a list of registered functions, placing each registered function in a separate row on Sheet1. Column A contains the full path and filename of the DLL or code resource, column B contains the function name, and column C contains the argument data type code.

theArray = Application.RegisteredFunctions
If IsNull(theArray) Then
    MsgBox "No registered functions"
Else
    For i = LBound(theArray) To UBound(theArray)
        For j = 1 To 3
            Worksheets("Sheet1").Cells(i, j).Formula = theArray(i, j)
        Next j
    Next i
End If