将字典绑定到GridView

Question

将字典绑定到GridView

asp.netvb.netdata-bindinggridviewdictionary

3

提到这个主题：Algorithm to count the time that occured on the same period，如何将字典绑定到 GridView？请查看答案。

我尝试添加一个 GridView 然后在代码后端中使用 GV.DataSource = timeRangeCounts 并绑定它，但是返回的结果为：

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？请查看下面的代码：

第一个帮助类用于保存准确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（类型为TimeRange）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

因此，我们可以使用上述方法编写以下算法：

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？

- mrjimoy_05

请展示一下您Gridview的代码，谢谢！ - Brian Webster

@Brian Webster：抱歉回复晚了。我已经添加了它，请看一下。它得到了结果，但是字典值没有返回任何值，只返回了“TimeRangeCounter”。 - mrjimoy_05

添加了 ToString() 的重写有帮助吗？ - Brian Webster

1个回答

网页内容由stack overflow 提供, 点击上面的

可以查看英文原文，
原文链接

- Brian Webster · Accepted Answer

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

这是输出结果

输入图像描述

如果我的某个类型的值是"MyClass?"怎么办？

Gridview将对"Value"单元格执行MyClass的ToString函数。

在您的示例中，重写此类的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“Value”是时间类型 TimeRangeCounter。

摘要

作者的代码存在两个问题。

问题1导致实际错误，通过遵循我的代码示例解决了该问题
问题2是Gridview中“Value”列使用自定义类时缺少ToString函数