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Description |
| Empty |
Used to indicate an uninitialized variable value. A variable value is uninitialized when it is first created and no value is assigned to it, or when a variable value is explicitly set to empty.
Example:
Dim x 'the variable x is uninitialized!
x="ff" 'the variable x is NOT uninitialized anymore
x=Empty 'the variable x is uninitialized!
Note: This is not the same as Null!!
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| IsEmpty() |
Used to test if a variable is uninitialized.
Example:
If (IsEmpty(x)) 'is x uninitialized?
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| Nothing |
Used to indicate an uninitialized object value, or to disassociate an object variable from an object to release system resources.
Example: Set myObject=Nothing
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| Is Nothing |
Used to test if a value is an initialized object.
Example:
If (myObject Is Nothing) 'is it unset?
Note: If you compare a value to Nothing, you will not get the right result! Example: If (myObject = Nothing) 'always false!
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| Null |
Used to indicate that a variable contains no valid data.
One way to think of Null is that someone has explicitly set the value to "invalid", unlike Empty where the value is "not set".
Note: This is not the same as Empty or Nothing!!
Example:
x=Null 'x contains no valid data
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| IsNull() |
Used to test if a value contains invalid data.
Example:
if (IsNull(x)) 'is x invalid?
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