how to handle properties with this FxCopAnalyzer warning: "CA2227: Set "Images" as read-only by removing the setter for the property" - vb.net

Question

What is this programme about:
This program was developed with the VB.Net language, the .NET Framework 4.8 and Visual Studio 2019 CE. The idea of this program is to run a rudimentary database. The list is similar to a classic Internet forum—there are threads, there are different numbers of postings in the threads and in each post there are different numbers of pictures and long texts. If the thread is selected using the ComboBox, all posts with their images and texts are displayed one below the other. When you click on a specific post, only its images are displayed.
The user can create threads and posts. For reasons of legibility, only extended Latin letters are allowed when writing the text (e.g. René, Chloë).
When you close the program, you will be asked whether you want to save the data. These data are read in when the program is loaded. If images are not found, their paths will be displayed in a window.
The user also has the option of searching through all threads and viewing the results with various sorting options. In this case, only the posts found are listed in the ListBox, and here, too, the user can select the posts individually.
The program also reads in user data when it starts. A user can log in and, depending on his role, has certain power to make decisions. A “normal” user can create threads and posts, but only an administrator or moderator can edit and delete texts. If you are not logged in, you can only read threads and posts.
What I would like to know from you
I use the FxCopAnalyzer, which is currently giving me 8 warnings. I am aware that it sometimes exaggerates a little or criticizes certain things that were done on purpose. But I'd like to let you guys have a look to make it better. What exactly is this supposed to mean: "CA2227: Set "Images" (Bilder) as read-only by removing the setter for the property". Because when I remove the setter, I get an error message.
I feel the same way with other properties in other classes. So I need to know, how to fix this, and I need a general solution. I appreciate.
Class structure
There is the class Forum, the class Class_Thread and the class Class_Post. Class_Thread inherits from forum. In the Class_thread there is a list(of Class_Post) which contains instances of Class_Post. ("The thread knows what posts it has"). In FormMain, a List(of Class_Thread) is created, in which the instances of Class_Thread are.
In Class_Post's constructor, the following parameters are transferred: 1) the heading of the posting, 2) the text, 3) the number, 4) images as List(Of System.Drawing.Bitmap), 5) the date, 6) the image paths As List(Of String).
Class_Post.vb
#Disable Warning CA1707 ' Bezeichner dürfen keine Unterstriche enthalten
Public Class Class_Post : Inherits Class_Forum
Private _ueberschrift As String = ""
Private _text_dazu As String = ""
Private _nummer As UInt16
Private _bilder As List(Of System.Drawing.Bitmap)
Private _erstelldatum_dieses_Posts As Date
Private _pfade_der_Bilder As List(Of String)
Public Property Ueberschrift As String
Get
Return _ueberschrift
End Get
Set(value As String)
_ueberschrift = value
End Set
End Property
Public Property Text_dazu As String
Get
Return _text_dazu
End Get
Set(value As String)
_text_dazu = value
End Set
End Property
Public Property Nummer As UShort
Get
Return _nummer
End Get
Set(value As UShort)
_nummer = value
End Set
End Property
Public Property Bilder As List(Of Bitmap)
Get
Return _bilder
End Get
Set(value As List(Of Bitmap))
_bilder = value
End Set
End Property
Public Property Erstelldatum_dieses_Posts As Date
Get
Return _erstelldatum_dieses_Posts
End Get
Set(value As Date)
_erstelldatum_dieses_Posts = value
End Set
End Property
Public Property Pfade_der_Bilder As List(Of String)
Get
Return _pfade_der_Bilder
End Get
Set(value As List(Of String))
_pfade_der_Bilder = value
End Set
End Property
Public Sub New(ByVal Ueberschrift As String, ByVal Text As String, ByVal nr As UInt16, ByVal uebergebene_Bilder As List(Of System.Drawing.Bitmap), ByVal _date As Date, ByVal Pfade As List(Of String))
Me.Ueberschrift = Ueberschrift
Me.Text_dazu = Text
Me.Nummer = nr
Me.Bilder = uebergebene_Bilder
Me.Erstelldatum_dieses_Posts = _date
Me.Pfade_der_Bilder = Pfade
End Sub
End Class
#Enable Warning CA1707 ' Bezeichner dürfen keine Unterstriche enthalten
This is in FormMain, where a new Instance of Class_Post is created This Sub is using a second Form from which the data is taken.
Private Sub Button_neueAntwort_Click(sender As Object, e As EventArgs) Handles Button_neueAntwort.Click
' doppelt abgesichert, falls die Variable SI aus irgendeinem Grunde nicht (-1) ist, obwohl sie das sollte.
If SI <> (-1) OrElse ComboBox1.SelectedItem IsNot Nothing Then
Using FA As New Form_Antwort
Dim DR As DialogResult = FA.ShowDialog(Me)
If DR = DialogResult.Yes Then
Dim neuerPost As New Class_Post(FA.Titel_des_Posts, FA.Beschreibung, CUShort(Liste_mit_allen_Threads(SI).Posts_in_diesem_Thread.Count + 1), FA.NeueListeBitmaps, Date.Now, FA.Liste_mit_Pfaden)
Liste_mit_allen_Threads(SI).Posts_in_diesem_Thread.Add(neuerPost)
alle_Posts_in_diesem_Thread_anzeigen()
End If
End Using
Else
MessageBox.Show("Bitte zuerst einen Thread auswählen.", "Info", MessageBoxButtons.OK, MessageBoxIcon.Information)
End If
End Sub

Answer 1

Thanks to Jimi and Craig, I can come up with a solution here. The thing is, unfortunately I let the FxCopAnalyzer influence me a bit. It had suggested using getters and setters instead of the normal fields, and that's why the warning I reported about came up. But the solution looks very simple, just use properties:
Public Class Class_Post : Inherits Class_Forum
Public ReadOnly Property Ueberschrift As String = ""
Public ReadOnly Property Text_dazu As String = ""
Public ReadOnly Property Nummer As UInt16
Public ReadOnly Property Bilder As List(Of System.Drawing.Bitmap)
Public ReadOnly Property Erstelldatum_dieses_Posts As Date
Public ReadOnly Property Pfade_der_Bilder As List(Of String)
Public Sub New(ByVal Ueberschrift As String, ByVal Text As String, ByVal nr As UInt16, ByVal uebergebene_Bilder As List(Of System.Drawing.Bitmap), ByVal _date As Date, ByVal Pfade As List(Of String))
Me.Ueberschrift = Ueberschrift
Me.Text_dazu = Text
Me.Nummer = nr 'kann maximal 65535 werden
Me.Bilder = uebergebene_Bilder
Me.Erstelldatum_dieses_Posts = _date
Me.Pfade_der_Bilder = Pfade
End Sub
End Class
Edit:
Of course, this is only true until you decide to create a button where a moderator wants to delete an image. Then, ReadOnly has to be removed again and the FxCopAnalyzer complains again.