将字典绑定到 GridView

Question

参考这个帖子：Algorithm to count the time that occured on the same period，如何将字典绑定到GridView？请看答案。

我尝试添加一个 GridView，然后在代码隐藏：GV.DataSource = timeRangeCounts 并绑定它，但作为回报：

The data source for GridView with id 'GV' did not have any properties or attributes from which to generate columns. Ensure that your data source has content.

我该怎么做？请看下面的代码：

---

第一个帮助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

第二个辅助类用于帮助字典了解一个键（TimeRange 类型）与另一个键的不同之处：

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

第三个帮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

所以使用上面我们应该可以写出这个算法：

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()

网格视图：

<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，但结果是这样的：

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？

Answer 1

这是一个网格视图

    <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>

这是将字典绑定到该 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

如果我的值属于“MyClass”类型怎么办？

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

在您的示例中，覆盖此类上的 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“价值”是时间TimeRangeCounter

总结

作者的代码有两个问题。

• 问题 1 产生了一个实际错误，按照我的代码示例解决了
• 问题 2 是 Gridview 的“值”列中使用的自定义类缺少 ToString 函数