C# 是否在LINQ select结果中添加计算字段？

我有一个LINQ查询（与EF一起使用）

基本上，我想根据另一列的值在selectresults中添加一列

我在DB表中有

PaymentDate

列，但没有

PaymentDate

列。如果

PaymentDate

列中的值为空，则表示付款为假，如果其中包含某个日期，则表示付款为真

这是我的问题，请指导我怎么做

 var selectedResults=
    from InvoiceSet in Invoices
    join BookedAreasSet in BookedAreas 
    on InvoiceSet.InvoiceID equals BookedAreasSet.InvoiceID
    join AreaSet in Areas on BookedAreasSet.AreaID equals AreaSet.AreaID
    select new     {InvoiceSet.InvoiceNumber,InvoiceSet.Amount,InvoiceSet.TotalDiscount,InvoiceSet.GST,       InvoiceSet.PaymentDate,InvoiceSet.ShoppingCentreID,BookedAreasSet.BookedAreaID,
AreaSet.Name,Here I want to add calculated value column based on InvoiceSet.PaymentDate value}

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我想你应该能做这样的事情

var selectedResults=
    from InvoiceSet in Invoices
    join BookedAreasSet in BookedAreas 
    on InvoiceSet.InvoiceID equals BookedAreasSet.InvoiceID
    join AreaSet in Areas on BookedAreasSet.AreaID equals AreaSet.AreaID
    select new { InvoiceSet.InvoiceNumber,InvoiceSet.Amount,InvoiceSet.TotalDiscount,InvoiceSet.GST,       
        InvoiceSet.PaymentDate,InvoiceSet.ShoppingCentreID,BookedAreasSet.BookedAreaID,
        AreaSet.Name,Paid = (InvoiceSet.PaymentDate == null) }