If Not dic1.TryGetValue(key1,val1) Then val1 = New Foo が多すぎて困る

DictExtension.vb

Imports System.Runtime.CompilerServices

Module DictExtension
    <Extension()>
    Public Function GetOr(Of K, V)(ByVal dict As IDictionary(Of K, V), key As K, ByVal f As Func(Of V)) As V
        Dim val As V = Nothing
        If Not dict.TryGetValue(key, val) Then
            val = f()
            dict.Add(key, val)
        End If
        Return val
    End Function
End Module