找到分钟。 vb.net 列表中的值答案

【问题标题】：To find min. value in a list in vb.net找到分钟。 vb.net 列表中的值
【发布时间】：2011-07-31 01:36:18
【问题描述】：

我有一个特定班级的列表。在此列表中，包含一个职位类别。该位置类包括 X 和 Y 坐标。我有当前坐标和列表中的坐标。我想计算 List 中每个项目的距离并找出哪个项目的距离最小。这是我的代码：

  For Each item As ITEMX In xHandle.ItemList

        Dim CurrX As Integer = txt_TrainX.Text
        Dim CurrY As Integer = txt_TrainY.Text
        Dim NextX As Integer = item.Position.x
        Dim NextY As Integer = item.Position.y

        Dim distance As Integer = DistanceBetween(CurrX, CurrY, NextX, NextY)


    Next

所以距离是我的坐标和项目之间的距离。我为列表中的每个项目计算它，但我如何找到最小的？

谢谢。

【问题讨论】：

标签： vb.net list max distance min

【解决方案1】：

在 VB.NET 中使用 Linq：

Dim CurrX As Integer = txt_TrainX.Text
Dim CurrY As Integer = txt_TrainY.Text

Dim NearestITEM = xHandle.ItemList.Min (Function(i) DistanceBetween(CurrX, CurrY, i.Position.x, i.Position.y));

有关 VB.NET 中 Linq 的一些信息和示例，请参阅http://msdn.microsoft.com/en-us/vbasic/bb688088

【讨论】：

【解决方案2】：

为最小值创建一个变量，并根据循环中的每个值检查它。

您应该从循环外的控件中解析文本，在循环内一遍又一遍地这样做是一种浪费。您还应该打开严格模式，这样您就不会进行不应该是隐式的隐式转换。

Dim minimal As Nullable(Of Integer) = Nothing

Dim CurrX As Integer = Int32.Parse(txt_TrainX.Text)
Dim CurrY As Integer = Int32.Parse(txt_TrainY.Text)

For Each item As ITEMX In xHandle.ItemList

  Dim NextX As Integer = item.Position.x
  Dim NextY As Integer = item.Position.y

  Dim distance As Integer = DistanceBetween(CurrX, CurrY, NextX, NextY)

  If Not minimal.HasValue or distance < minimal.Value Then
    minimal.Value = distance
  End If

Next

【讨论】：

感谢您的回答。我认为他们会提供帮助。

【解决方案3】：

以@Yahia 的 LINQ 回答为基础，获取项目和项目的距离。

Dim CurrX = CInt(txt_TrainX.Text)
Dim CurrY = CInt(txt_TrainY.Text)

Dim itemsWithDistance = (From item in xHandle.ItemList
                         Select New With {.Item = item, 
                                          .Distance = DistanceBetween(CurrX, CurrY, item.Position.x, item.Position.y)}).ToList()

' At this point you have a list of an anonymous type that includes the original items (`.Item`) and their distances (`.Distance`).
' To get the one with the smallest distance you can do.
Dim nearestItem = itemsWithDistance.Min(Function(i) i.Distance)

' Then to see what that distance was, you can
Console.WriteLine(nearestItem.Distance) 

' or you can access nearestItem.Item to get at the source item.

【讨论】：