c#忍者脚本无效toke'='；在类结构中，成员声明

cs1519错误代码。我在《忍者》中使用了c#，我有以下错误

    [Display(Name = "Buy", GroupName = "01. Profile", Order = 20)]
    public System.Windows.Media.Brush BuyLadderBrush// here it showing class member declaratione expected
    { get; set; } =  Brushes.LightGreen ; //in this line am getting invalid token ';' and '=' eror
    [Browsable(false)]
    public string BuyLadderBrushSerializable

二,

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你的项目目标是哪一个C#和.NET版本？4.5.NET我在eby上使用这个ninjatrader，我需要在ninjascript上工作。

    protected void DisposeUnmanagedGraphics()
    {
        BuyLadderBrushDx?.Dispose(); BuyLadderBrushDx = null;//all this case expression expected  error 
        SellLadderBrushDx?.Dispose(); SellLadderBrushDx = null;
        PositiveDeltaBrushDx?.Dispose(); PositiveDeltaBrushDx = null;
        NegativeDeltaBrushDx?.Dispose(); NegativeDeltaBrushDx = null;
        ChartBackgroundBrushDx?.Dispose(); ChartBackgroundBrushDx = null;
    }