AllowNull Property | Spread Windows Forms 13.0 Product Documentation

AllowNull Property

In This Topic

Gets or sets whether the control considers a null value valid.

Syntax

Visual Basic
C#

'Declaration
 
Public Overridable Property AllowNull As Boolean

'Usage
 
Dim instance As SuperEditBase
Dim value As Boolean
 
instance.AllowNull = value
 
value = instance.AllowNull

public virtual bool AllowNull {get; set;}

Property Value

Boolean value: true to allow null as user input; false otherwise

Remarks

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

Press F2.
Delete the contents of the edit control.
Call the SetNull method.
Call the ClearAll method.
Select the contents of the control and call the Clear method.

This property is available from the SuperEditBase class.

This property must be set to true for the NullColor property to work correctly.

You can return whether a control contains the null value by calling the IsNull method.

Example

private void Form1_Load(object sender, System.EventArgs e)
{
   control.NullColor = Color.Coral;
   control.AllowNull = true;
   control.CausesValidation = true;
   control.Text = "";
}

private void button1_Click(object sender, System.EventArgs e)
{
   control.ResetNullColor();
}

Visual Basic

Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
   control.NullColor = Color.Coral
   control.AllowNull = True
   control.CausesValidation = True
   control.Text = ""
End Sub

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
   control.ResetNullColor()
End Sub

Reference

SuperEditBase Class
SuperEditBase Members
NullColor Property
Text Property
SetNull Method
IsNull Method

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