asp.net - 将字典绑定(bind)到 GridView

Question

引用此帖子:Algorithm to count the time that occured on the same period 、如何将字典绑定(bind)到GridView上？请看一下答案。

我尝试添加一个 GridView，然后在代码隐藏中:GV.DataSource = timeRangeCounts 并绑定(bind)它，但作为返回:

ID 为“GV”的 GridView 数据源没有任何用于生成列的属性或特性。确保您的数据源有内容。

我怎样才能做到这一点？请看下面的代码:

<小时/>

第一个帮助器类用于保存精确匹配和子范围匹配的计数:

Public Class TimeRangeCounter
    Property ExactRangeMatch as Integer
    Property SubRangeMatch as Integer
End Class

第二个帮助器类用于帮助字典了解一个键(TimeRange 类型)与另一个键有何不同:

Public Class TimeRangeEqualityComparer 
    Implements IEqualityComparer(Of TimeRange)

    Public Overloads Function Equals(left As TimeRange, right As TimeRange) _
            As Boolean Implements IEqualityComparer(Of TimeRange).Equals           

        Return left.ToString = right.ToString   
    End Function

    Public Overloads Function GetHashCode(range As TimeRange) _
            As Integer Implements IEqualityComparer(Of TimeRange).GetHashCode

        return range.ToString().GetHashCode()
    End Function

End Class

第三个辅助类存储范围的开始和结束时间:

Public Class TimeRange 
    Private readonly _start
    Private readonly _end

    Public Readonly Property Start 
        Get
           return _start
        End Get
    End Property

    Public Readonly Property [End] 
        Get
           return _end
        End Get
    End Property

    Public Sub New(start As String, [end] As string)
        Me._start = start
        Me._end = [end]
    End Sub

    Public Overrides Function ToString() as String
       Return String.Format("{0}-{1}", Start, [End])
    End Function

End Class

所以使用上面的内容我们应该能够编写这个算法:

Dim columnLength As Integer = 5
Dim timeStart() As String = {"08.00", "08.00", "10.00", "08.00", "08.00"}
Dim timeEnd() As String = {"08.50", "11.50", "11.00", "09.00", "08.50"}
Dim comparer As New TimeRangeEqualityComparer()
Dim timeRangeCounts As New Dictionary(Of TimeRange, TimeRangeCounter)(comparer)

'Count exact range matches while building dictionary
For i = 0 to columnLength - 1
  Dim key As TimeRange = New TimeRange(timeStart(i), timeEnd(i))

  If timeRangeCounts.ContainsKey(key)
      timeRangeCounts(key).ExactRangeMatch += 1
  Else
      Dim counter =  New TimeRangeCounter()
      counter.ExactRangeMatch = 1
      timeRangeCounts(key) = counter
  End If        

Next           

'Count sub ranges          
For Each kvp in timeRangeCounts
    For Each key in timeRangeCounts.Keys
        If kvp.key.Start >= key.Start AndAlso _ 
           kvp.Key.End <= key.End AndAlso _
           kvp.key.ToString <> key.ToString then           

            kvp.Value.SubRangeMatch += 1
        End If
    Next
Next

'Console.WriteLine(timeRangeCounts)
    GV.DataSource = timeRangeCounts
    GV.DataBind()

GridView :

<asp:GridView ID="GV" runat="server">
    <Columns>
        <asp:BoundField DataField="Key" HeaderText="Dictionary Key" />
        <asp:BoundField DataField="Value" HeaderText="Dictionary Value" />
    </Columns>
</asp:GridView>

然后我尝试运行它，但结果如下:

Dictionary Key    Dictionary Value
08:00:00-08:50:00 TimeRangeCounter
08:00:00-09:40:00 TimeRangeCounter
10:00:00-11:40:00 TimeRangeCounter
...               ...

代码有什么问题吗？

Answer 1

这是一个 Gridview

    <asp:GridView ID="GV" runat="server" AutoGenerateColumns="false">
        <Columns>
            <asp:BoundField DataField="Key" HeaderText="Dictionary Key" />
            <asp:BoundField DataField="Value" HeaderText="Dictionary Value" />
        </Columns>
    </asp:GridView>

这里是将字典绑定(bind)到 Gridview 的代码

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
    Dim D As New Dictionary(Of Integer, String)
    D.Add(1, "One")
    D.Add(2, "Two")
    D.Add(3, "Three")
    GV.DataSource = D
    GV.DataBind()
End Sub

这是输出

如果我的值是某种类型“MyClass”怎么办？

Gridview 将针对每个“Value”单元格执行 MyClass 的 ToString 函数。

在您的示例中，重写此类上的 ToString 函数

Public Class TimeRangeCounter
    Property ExactRangeMatch as Integer
    Property SubRangeMatch as Integer
End Class

这是必要的，因为您的“值”是时间TimeRangeCounter

摘要

作者的代码有两个问题。

• 问题 1 生成了一个实际错误，并通过遵循我的代码示例解决了
• 问题 2 是 Gridview 的“Value”列中使用的自定义类缺少 ToString 函数