IsNull
Returns a Boolean indicating whether an expression contains no valid data (Null).
Syntax: IsNull( expression )
- expression
- required A Variant containing a numeric or string expression.
IsNull returns True if expression is Null; otherwise, False. If expression contains more than one variable, Null in any constituent variable causes the whole expression to evaluate to Null, and IsNull to return True.
The Null value indicates that a Variant holds no valid data. Null is not the same as Empty (a variable that has not yet been initialized), nor the same as a zero-length string (""), which is sometimes called a null string.
Important
Use IsNull to determine whether an expression contains a Null value. Comparisons such as If Var = Null and If Var <> Null are always False, because any expression involving Null is itself Null, and a Null comparison is treated as False.
Example
This example uses IsNull to determine whether a variable contains a Null.
Dim MyVar As Variant
Dim MyCheck As Boolean
MyCheck = IsNull(MyVar) ' False — MyVar is Empty.
MyVar = ""
MyCheck = IsNull(MyVar) ' False — empty string is not Null.
MyVar = Null
MyCheck = IsNull(MyVar) ' True.