IsNull Function |  |
-- todo --
Returns true (.T.) if an expression evaluates to a null value; otherwise, IsNull( ) returns false (.F.).
Namespace: XSharp.VFP
Assembly: XSharp.VFP (in XSharp.VFP.dll) Version: 2.19
SyntaxFUNCTION IsNull( eExpression ) AS LOGIC CLIPPER
[ClipperCallingConventionAttribute(new string[] { ... })] public static bool IsNull( Usual eExpression = default )
Parameters
- eExpression (Optional)
- Type: Usual
Specifies the expression to evaluate.
Return Value
Type: LogicLogical
Remarks
Use IsNull( ) to determine if the contents of a field, memory variable, or array element contains a null value,
or if an expression evaluates to a null value.
ExamplesX#
1Store .NULL. To mNullvalue // Store a null value to a memory variable 2Clear 3? mNullvalue // Display the value of the memory variable 4? IsNull(mNullvalue) // Returns .T., indicating a null value 5? TYPE('mNullvalue') // Returns L, indicating a logical value 6? (mNullvalue = .NULL.) // Returns .NULL., bad test for null values
See Also