Spread Windows Forms 9.0 Product Documentation
IsNull Method
Example 


Gets whether the control contains a null value.
Syntax
'Declaration
 
Public Overridable Function IsNull() As Boolean
'Usage
 
Dim instance As SuperEditBase
Dim value As Boolean
 
value = instance.IsNull()
public virtual bool IsNull()

Return Value

true if the control contains the null value; false otherwise
Remarks

When this property returns true, the control contains the null value.

When the AllowNull property is set to true, the control accepts null values, and the user can provide a null value in the following ways:

The AllowNull property must be set to true for the IsNull method and NullColor property to work correctly.

Example
privatevoidForm1_Load(objectsender,System.EventArgse)
{
control.AllowNull=true;
}

privatevoidcontrol_MouseDown(objectsender,System.Windows.Forms.MouseEventArgse)
{
boolbvalue;
bvalue=control.IsNull();
if(bvalue)
{
control.Value=500;
}
}
PrivateSubForm1_Load(ByValsenderAsSystem.Object,ByValeAsSystem.EventArgs)HandlesMyBase.Load
control.AllowNull=True
EndSub

PrivateSubcontrol_MouseDown(ByValsenderAsObject,ByValeAsSystem.Windows.Forms.MouseEventArgs)HandlesCurrency1.MouseDown
DimbvalueAsBoolean
bvalue=control.IsNull()
IfbvalueThen
control.Text=500
EndIf
EndSub
Requirements

Target Platforms: Windows 2000 Professional (SP4), Windows 2000 Server, Windows 2003 Server (SP1), Windows Server 2012 R2, Windows 2008, Windows XP (SP2), Windows Vista, Windows 7, Windows 8, Windows 8.1, Windows 10

See Also

Reference

SuperEditBase Class
SuperEditBase Members
AllowNull Property
NullColor Property
SetNull Method
Text Property
Clear Method
ClearAll Method

 

 


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