如何将附加参数传递给谓词？

发布于 2024-09-14 21:27:30 字数 271 浏览 3 评论 0原文

我的问题是通过传递特定日期从（日历）列表中查找确切的一个日历对象。我了解了谓词，但不确定是否向其传递参数。

colorcode 是列表（日历），日历类有一个名为 DtmDate 的属性，我想与它进行比较并返回所需的对象。

Dim a As Calendar = colourcode.Find(AddressOf New Calendar.FindByDate)

我从谷歌得到了谓词样本并达到了现在。但不知道如何将我的参数（即日期）传递给它。

原文

My issue is to Find exact one Calendar object from a List Of(Calendar) by passing a particular date. I got to know about the predicate but not sure about passing parameter to it.

colorcode is List Of (Calendar) and calendar class has a property called DtmDate with which I want to compare and return the desired object.

Dim a As Calendar = colourcode.Find(AddressOf New Calendar.FindByDate)

I got the predicate samples from Google and reached till now. But not sure how to pass my parameter i.e. date to it.

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聆听风音 2024-09-21 21:27:30

您必须创建自己的谓词。您可以使用 lambda 来做到这一点，并通过将局部变量“提升”到其中，您可以对其进行参数化。下面是 .NET 3.5/Visual Studio 2008 的一个有点愚蠢的示例：

Dim lookFor As String = "e"
Dim predicate = Function(s as String) s.Contains(lookFor)

Dim list As New List(Of String)
list.Add("alfa")
list.Add("beta")
list.Add("gamma")
list.Add("delta")
Dim foundString As String = list.Find(predicate)

请注意如何更改 lookFor 的值以搜索其他字符串。

在 .NET 4/Visual Studio 2010 中，Visual Basic 具有更具表现力的 lambda 表达式：

You will have to create your own predicate. You can do that using a lambda and by "lifting" local variables into it you can parametrize it. Here is an somewhat silly example for .NET 3.5/Visual Studio 2008:

Dim lookFor As String = "e"
Dim predicate = Function(s as String) s.Contains(lookFor)

Dim list As New List(Of String)
list.Add("alfa")
list.Add("beta")
list.Add("gamma")
list.Add("delta")
Dim foundString As String = list.Find(predicate)

Notice how you can change the value of lookFor to search for other strings.

In .NET 4/Visual Studio 2010 Visual Basic has more expressive lambda expressions:

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