I was wondering whether it’s possible to validate a required size for an icon

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Asked: May 13, 20262026-05-13T12:05:25+00:00 2026-05-13T12:05:25+00:00

I was wondering whether it’s possible to validate a required size for an icon

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I was wondering whether it’s possible to validate a required size for an icon before trying:

Dim myIcon = New Icon(theIcon, requestedSize).

This falls over for negative numbers, so that’s an easy check.

It appears it falls over if the number is less than half of the smallest icon.
I’ve looked at the icon class but can see nothing for extracting the sizes.

ETA:

This is pretty annoying. You can put Int32.MaxValue in and it chooses the largest icon. Why it doesn’t choose the smallest icon, as long as size > 0 I don’t know.
If I can determine the size of the smallest icon, then I can do that myself – with no need to throw an exception.

ETA:

Here’s some VB code for anyone who’s interested:

//Returns an array of IconMetaData which contains, amongst other things, the size of
// each image in the icon.

<Extension()> _
Public Function GetMetaData(ByVal icon As Icon) As IconMetaData()
    Using s As New System.IO.MemoryStream
        icon.Save(s)
        Using r As New BinaryReader(s)
            s.Position = 0
            Dim Header As New IconHeader(r)
            Dim Data As New List(Of IconMetaData)
            For i As Integer = 0 To Header.NumberOfIcons - 1
                Dim d As New IconMetaData(r)
                *See note below. 
                If d.Height <> 0 AndAlso d.Width <> 0 Then
                    Data.Add(d)
                End If
            Next
            Return Data.ToArray
        End Using
    End Using
End Function

Private Class IconHeader

    Public ReadOnly NumberOfIcons As Short

    Public Sub New(ByVal r As BinaryReader)
        r.ReadInt16() //Reserved
        r.ReadInt16() //Type, 0=Bitmap, 1=Icon
        Me.NumberOfIcons = r.ReadInt16
    End Sub

End Class

Public Class IconMetaData

    Public ReadOnly Width As Byte
    Public ReadOnly Height As Byte
    Public ReadOnly ColorCount As Byte
    Public ReadOnly Planes As Short
    Public ReadOnly BitCount As Short

    Friend Sub New(ByVal r As BinaryReader)
        Me.Width = r.ReadByte
        Me.Height = r.ReadByte
        Me.ColorCount = r.ReadByte
        r.ReadByte() //Reserved
        Me.Planes = r.ReadInt16
        Me.BitCount = r.ReadInt16
        r.ReadInt32() //Bytes in res
        r.ReadInt32() //Image offset
    End Sub

End Class

*Note: From the couple of icons i’ve tested this with, the first entry has dimensions of (0,0). I don’t know why, and I can’t be sure that all icons have this entry, or that it’s always the first. Therefore, I check each one.

ETA: On further investigation, i’ve found that 0 is used to indicate an icon of size 256.