I have a custom control that has a SelectedValue property. It is basically a ComboBox control, if that helps. Anyway, I have a business object that I'm binding to this control. In some cases, the business object property that I'm binding to the control is a System.GUID, in other cases, it is a System.Int32 or System.String.
My delimea is that if the custom control's internal _selectedValue member is Nothing, because the user never selected a value or the selection was cleared, I want to return a valid data type to my custom business object.
So if I'm binding to a property on my business object that is a System.GUID and _selectedValue is Nothing, then I want to return System.GUID.Empty.
System.Int32 and _selectedValue Is Nothing, then 0.
System.String and _selectedValue Is Nothing, then System.String.Empty.
I'll be fine with hardcoding the "default null value" into my custom control based on a given data type, but don't know how to implement this. It would look something like this..
Get
Select Case "Custom Business Object Property Type"
Case System.GUID
Return System.GUID.Empty
Case System.Int32
Return 0
Case System.String
Return System.String.Empty
Case System.DateTime
Return System.DateTime.MinValue
End Select
End Get
I'm not sure how to detect which default value to pass back when the _selectedValue is Nothing. Any help is appreciated. Thanks!
Greg
'================================================
'Code from the form where I'm using the custom control and business object
'================================================
'Private member variable for form
Private _myCustomBusinessObject as New MyCustomBusinessObject()
Public Sub Form_Load....
'Load Data Into Custom Business Object
_myCustomBusinessObject.Load(1)
'Bind Custom Control's SelectedValue to _myCustomBusinessObject.PersionGUID
myCustomControl.DataBindings.Add("SelectedValue", _myCustomBusinessObject,
"PersonGUID")
End Sub
'================================================
'Code from the custom control
'================================================
'Private member variable for custom control
Private _selectedValue As System.Object = Nothing
'Custom Control SelectedValue Property
Public Property SelectedValue() As System.Object
Get
Return _selectedValue
End Get
Set (ByVal Value as System.Object)
'Is this value valid, if so set member variable
If ValidValue(Value) Then
_selectedValue = Value
Else
_selectedValue = Nothing
End If
End Get
End Property
'================================================
'Code from the custom business object
'================================================
'Private member variable for custom business object
Private _personGUID as System.GUID = System.GUID.Empty
'PersonGUID Public Property
Public Property PersonGUID() As System.GUID
Get
Return _personGUID
End Get
Set (ByVal Value as System.GUID)
_personGUID = Value
End Set
End Property
Custom Control With SelectedValue Property - How to determine correct "default" data type to return?
FloridaAviator
in that case:
if (o is int)
{
// maybe you should return int.MaxValue/MinValue
return 0;
}
if (o is string)
{
return string.empty;
}
if (o is GUID)
{
return GUID.empty;
}
Hope this is what you have meant.
Bjornar
Dim x As Type = Me.DataBindings.Item("SelectedValue").DataSource.GetType Dim y As System.Reflection.PropertyInfo = x.GetProperty(Me.DataBindings.Item("SelectedValue").BindingMemberInfo.BindingField) Select Case y.PropertyType.FullName.ToLower
Case "system.guid"
Return System.Guid.Empty
Case "system.datetime"
Return System.DateTime.MinValue
Case "system.boolean"
Return False
Case "system.string"
Return System.String.Empty
Case Else
Return 0
End Select