Click or drag to resize

IsNull Function

X#
-- 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: 2.21
Syntax
 FUNCTION IsNull(
	eExpression
) AS LOGIC CLIPPER
Request Example View Source

Parameters

eExpression (Optional)
Type: Usual
Specifies the expression to evaluate.

Return Value

Type: Logic
Logical
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.
Examples
X#
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