Clean elegant solution to form-class level component collection initializing before Initialize Component?

Question

I am converting an old Vb6 solution to .net 2.0 in vs2010. I've been working in C# for about 3 years now and .net for 5. I don't recall having this problem in C#, but if I want initialize a readonly collection of DerivedControlFoo Is there a clean way to do it besides creating a sub to do it all off somewhere else? I'd love to be able to do it at the class level at the declaration for readability and simplicity.

Example:

Private _formattedFormulaText As IEnumerable(Of Label) = New List(Of Label) From { _
 FormulaLabels0, FormulaLabels1, lblBrownFormula, FormulaLabels3, lblGreenFormula, _
      lblOrangeFormula, lblRedFormula, FormulaLabels7, lblFormulaTotal}

Doing it the straightforward easy way, results in the collection being filled with {nothing,..,nothing}

score 0 · Accepted Answer · answered Feb 07 '11 at 16:37

This is not thread safe, but works very well for my purposes:

Solution in use:

 Private _formattedFormulaText As New Lazy(Of IEnumerable(Of Label))(Function() New List(Of Label) From { _
 FormulaLabels0, FormulaLabels1, lblBrownFormula, FormulaLabels3, lblGreenFormula, _
      lblOrangeFormula, lblSRedFormula, FormulaLabels7, lblFormulaTotal})

drawbacks - all code touching the variable has to add an accessor .value. My code has 5 of these lazy collections and 1-2 touchpoints per collection usually in the same function.

Drawback illustration:

Dim clearText = Sub(c As Control) c.Text = String.Empty
        _formattedFormulaText.ToList.ForEach(clearText)

becomes

Dim clearText = Sub(c As Control) c.Text = String.Empty
        _formattedFormulaText.Value.ToList.ForEach(clearText)

Not compliant with good practices for debugger display used in .net 4, but would be easy to add in using reflector

Please note a property could have been used to eliminate the need to .value in the touchpoints:

   Private ReadOnly Property FormattedText As IEnumerable(Of Label)
        Get
            Return _formattedFormulaText.Value
        End Get
    End Property

supporting class:

''' <summary>
''' translated from http://msdn.microsoft.com/en-us/vcsharp/bb870976.aspx
''' </summary>
Public Class Lazy(Of T)
    Private _func As Func(Of T)
    Private _result As T
    Private _hasValue As Boolean
    Public Sub New(ByVal func As Func(Of T))
        _func = func
        _hasValue = False
    End Sub
    Public ReadOnly Property Value As T
        Get
            If Me._hasValue = False Then
                _result = _func()
                _hasValue = True
            End If
            Return _result
        End Get
    End Property

End Class

design based on MSDN's article Lazy Computation in C# Also with assistance from Reflector against

assembly\NativeImages_v4.0.30319_32\mscorlib\246f1a5abb686b9dcdf22d3505b08cea\mscorlib.ni.dll

Clean elegant solution to form-class level component collection initializing before Initialize Component?

1 Answers1