vb.net LINQ to Object grouping by create date - vb.net

Question

I have a .net webapi endpoint that currently returns an array of objects (JSON).
I'm trying to group the items by the created date, but i can't work out the LINQ statement to achieve this.
Class:
Public Class mImage
Public Property fileName As String
Public Property id As Guid
Public Property description As String
Public Property createDate As DateTime
End Class
Public Class mImageParent
Public Property groupDate As DateTime
Public Property images As List(Of mImage)
Public Property groupCount As Integer
End Class
My current JSON return looks like this:
obj: [
{"fileName":"a","id":"1","createDate":"1-1-2020"},
{"fileName":"b","id":"2","createDate":"1-1-2020"},
{"fileName":"c","id":"3","createDate":"2-1-2020"}
]
Where i'm trying to return it as:
obj: {"groupDate":"1-1-2020",
"images": [
{"fileName":"a","id":"1","createDate":"1-1-2020"},
{"fileName":"b","id":"2","createDate":"1-1-2020"}
]},
{"groupDate":"2-1-2020",
"images": [
{"fileName":"c","id":"3","createDate":"2-1-2020"}
]}
Current Code that just selects without grouping LINQ(vb.net):
Dim imageResult = (From p In db.file_images Where p.user_id = userIdParam).ToList()
For each p in imageResult
mImageList.Add(New mImage With {.id = p.image_id, .description = p.image_desc, .fileName = p.image_file, .createDate= p.create_timestamp})
Next
I can't sort out how to select into groups. The for..each is required because some other stuff goes on before the item is added to the list.
The syntax i have (not working, can't work out the select into):
Dim imageResultGroup = (From p in db.file_images where p.user_id = userIDParam).GroupBy(Function(g) g.create_timestamp).Select(Function(grp) New mImageParent with {.groupDate = grp.Key, images = grp.ToList()})

Answer 1

The following method will return an anonymous object that has the following properties:
createdDate - the grouped on date
images - a collection of mImage
VB.Net Code:
Dim groupedImages =
From fileImage As mImage In fileImages
Select fileImage
Group By createdDate = fileImage.createDate
Into images = Group
Order By createdDate
With a little refactoring, you can rename the createdDate property to groupDate.