将字典绑定到 GridView [英] Bind Dictionary to GridView

问题描述

参考此线程:算法统计同一时期发生的时间，如何将字典绑定到GridView?请看一下答案.

Referring to this thread: Algorithm to count the time that occured on the same period, how to bind the dictionary to the GridView? Pls take a look to the answer.

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

I tried to add a GridView and then on the code-behind: GV.DataSource = timeRangeCounts and bind it, but in return:

id 为GV"的 GridView 的数据源没有任何可用于生成列的属性或属性.确保您的数据源有内容.

我该怎么做?请看下面的代码:

How can I do that? Please take a look at the code below:

第一个辅助类用于保存精确和子范围匹配的计数:

The first helper class is used to hold the counts of exact and sub range matches:

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)与另一个键的区别:

The second helper class is used to help the dictionary know how one key (of type TimeRange) differs from another:

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

第三个辅助类存储一个范围的开始和结束时间:

The Third helper class stores the start and end times of a range:

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

所以使用上面的我们应该可以写出这个算法:

So using the above we should be able to write this algorithm:

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，但结果如下:

Then I tried to run it but the result is like:

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?

推荐答案

这里是 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

如果我的值是某种类型的MyClass"怎么办?

Gridview 将根据值"单元格执行 MyClass 的 ToString 函数.

The Gridview will execute the ToString function of MyClass, per "Value" cell.

在您的示例中，覆盖此类上的 ToString 函数

In your example, Override the ToString function on this class

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

This is necessary because your "Value" is of time TimeRangeCounter

总结

作者的代码有两个问题.

The Author's code had two problems.

• 问题 1 产生了实际错误，并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

这篇关于将字典绑定到 GridView的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！