没有可访问的“Sum”接受此数目的类型实参

   Private m_skus As System.Collections.Generic.Dictionary(Of String, SKUItem)
 Public ReadOnly Property Stock() As Integer
            Get
                Return Me.m_skus.Values.Sum(Of SKUItem)(Function(sku As SKUItem) sku.Stock)
            End Get
End Property

提示错误:

没有可访问的“Sum”接受此数目的类型实参，因此重载决策失败。
Dictionary
[解决办法]

  Private m_skus As System.Collections.Generic.Dictionary(Of String, SKUItem)
    Public ReadOnly Property Stock() As Integer
        Get
            Return Me.m_skus.Values.Sum((Function(sku As SKUItem) sku.Stock))
        End Get
    End Property