Readonly PropertyGrid

Question

I'm using a PropertyGrid in an application I am writing to allow users to view and sometimes edit instances of my objects. Sometimes the user may have a file open in read/write mode where they can make changes to the file through the property grid. In other cases they may have a file open in read only mode, and should not be able to make any changes to the objects through the PropetyGrid. My classes also have dynamic properties which are returned by implementing ICustomTypeDescriptor. Which is why I really want to take advantage of the built in flexibility of a PropertyGrid control.

There doesn't seem to be an easy way to set a Property-grid to a read only mode. If I disable a PropertyGrid this also prevents the user from scrolling the list. So I'm thinking the best way to do this is to add ReadOnlyAttributes to the properties at run-time. Is there some other way?

Answer 1

Since you are implementing ICustomTypeDescriptor there is no need to add any attributes; you can just override IsReadOnly on the PropertyDescriptor. I'm thinking it should be pretty simple to write an intermediary type that mimics (via ICustomTypeDescriptor and TypeConverter) a wrapped type but always returns readonly PropertyDesciptor instances? Let me know if you want an example (it isn't trivial though).

You might also want to check whether something like this offers it built it.

Answer 2

I have found a very quick solution for thoses who do not care about the propertygrid being grayed out.

TypeDescriptor.AddAttributes(myObject, new Attribute[]{new ReadOnlyAttribute(true)});
propertyGrid1.SelectedObject = myObject;

Answer 3

My advice would be to write a custom control that inherits from the propertygrid control, and in that custom control, have a boolean value of readonly, and then override some things and check, if(readonly) then cancel the action

Answer 4

I ran into this one. I wanted a control that was read only but not grayed out.

Inherit from the property grid control and create your own read only version by adding the following code to override key presses

#Region "Non-greyed read only support"

Private isReadOnly As Boolean
Public Property [ReadOnly]() As Boolean
    Get
        Return Me.isReadOnly
    End Get
    Set(ByVal value As Boolean)
        Me.isReadOnly = value
    End Set
End Property


Protected Overrides Function ProcessDialogKey(ByVal keyData As Keys) As Boolean
    If Me.isReadOnly Then Return True
    Return MyBase.ProcessDialogKey(keyData)
End Function

Public Function PreFilterMessage(ByRef m As Message) As Boolean
    If m.Msg = &H204 Then 'WM_RBUTTONDOWN
        If Me.isReadOnly Then Return True
    End If
    Return False
End Function
#End Region