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I am trying to
list
some
properties
names by
category
attribute and put them into a
variable
. For example, to get all
properties
names which "belong" to category
Appearance
and put them into a
variable
.
I have a similar example which resets specific properties, but I have to add them one by one (which I want to avoid) and not get them by category name.
vb.net Code:
Dim _Form As Form = CType(Me, Form)
Dim ListOfPropertyNames As New List(Of String) From {"BackColor", "ForeColor"}
For Each _Property In ListOfPropertyNames
Dim _PropertyDescriptor As PropertyDescriptor = TypeDescriptor.GetProperties(_Form)(_Property)
If _PropertyDescriptor.CanResetValue(_Form) Then
If _PropertyDescriptor.GetValue(_Form) IsNot Nothing Then
_PropertyDescriptor.ResetValue(_Form)
End If
End If
Next
Just looking at the documentation for the PropertyDescriptor class I can see that it has an Attributes property. Without having tested anything, I would guess you could use something like this:
vb.net Code:
Dim category = DirectCast(_PropertyDescriptor.Attributes(GetType(CategoryAttribute)), CategoryAttribute)
If category.Category = someParticularCategoryName AndAlso _PropertyDescriptor.CanResetValue(_Form) Then
vb.net Code:
Dim PropertyCollection As List(Of PropertyDescriptor) = TypeDescriptor.
GetProperties(_Control).
OfType(Of PropertyDescriptor).
Where(Function(item) item.Category = "Appearance").
OrderBy(Function(item) item.Category).
ThenBy(Function(item) item.DisplayName).
ToList()
Edited
after
jmcilhinney
's correction
below
!!!
Ha! The Category property is right below the Attributes property in the documentation and I didn't even notice it because I was specifically looking for attributes. Mind you, it does mention the CategoryAttribute in the description of the Category property, so I probably should have seen it.
As for your code, it may not matter anyway as the LINQ provider may optimise it but it seems to me that the Where should come before the OrderBy and, given that you're filtering by Category, you should be sorting only by DisplayName. Have you read something that indicates that sorting before filtering is preferred? If you consider the amount of work that would be done if each of those three operations were done literally as written then 'OrderBy(Function(item) item.Category).ThenBy(Function(item) item.DisplayName).Where(Function(item) item.Category = "Appearance")' would be much less efficient than 'Where(Function(item) item.Category = "Appearance").OrderBy(Function(item) item.DisplayName)'.
As for your code, it may not matter anyway as the LINQ provider may optimise it but it seems to me that the Where should come before the OrderBy and, given that you're filtering by Category, you should be sorting only by DisplayName. Have you read something that indicates that sorting before filtering is preferred? If you consider the amount of work that would be done if each of those three operations were done literally as written then 'OrderBy(Function(item) item.Category).ThenBy(Function(item) item.DisplayName).Where(Function(item) item.Category = "Appearance")' would be much less efficient than 'Where(Function(item) item.Category = "Appearance").OrderBy(Function(item) item.DisplayName)'.
Hm, you are right! And it does the "work" even if I use it without
OrderBy
and
ThenBy
.
vb.net Code:
Dim PropertyCollection As List(Of PropertyDescriptor) = TypeDescriptor.
GetProperties(_Control).
OfType(Of PropertyDescriptor).
Where(Function(item) item.Category = "Appearance").
ToList()
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