Bind Dictionary to GridView

Question

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.

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

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.

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

---

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

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

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

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()

The 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>

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
...               ...

What's wrong with the code?

Answer 1

Here is a 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>

Here is code to bind a dictionary to that Gridview

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

Here is the output

What if my Value of of some type "MyClass?"

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

In your example, Override the ToString function on this class

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

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

Summary

The Author's code had two problems.

• Problem 1 was generating an actual error and was solved by following my code example
• Problem 2 was the lack of a ToString function for the custom class used in the "Value" column of the Gridview