How to show the top-so-many or bottom-so-many records in a filter in WinForms GridGroupingControl?

3 mins read

Filtering

The QueryRecordMeetsFilterCriteria event has to be handled to get this behavior. A Hashtable is used to handle the values that are to be filtered at the top and bottom. The following sample displays the first 2 and last 2 records in a filter. The Hashtable is filled by using the user defined function, SetPositionFilter().

To perform a filter that restricts the filtered set to a certain number of elements, you have to filter twice. In the first pass, you get the total set of records that satisfies the filter. Then these records are numbered by using an unbound column populated indirectly with the SetPositionFilter method. Once the unbound column is populated with a position index value, you can then apply a second filter to select the first so-many or last so-many records.

//events triggered on the form load.
this.gridGroupingControl1.TableDescriptor.QueryValue += new FieldValueEventHandler(unboundField_QueryValue);
this.gridGroupingControl1.QueryRecordMeetsFilterCriteria += gridGroupingControl1_QueryRecordMeetsFilterCriteria;
this.gridGroupingControl1.FilterBarSelectedItemChanged += gridGroupingControl1_FilterBarSelectedItemChanged;
// Gets the filterbar selected text. 
void gridGroupingControl1_FilterBarSelectedItemChanged(object sender, FilterBarSelectedItemChangedEventArgs e)
{
   if(searchtext != e.SelectedText && searchtext != null)
   {
      restrict = false;
   }
   SetPositionInFilter();
   searchtext = e.SelectedText;
}
//Gets the checkBox values in a hashtable.
private void unboundField_QueryValue(object sender, FieldValueEventArgs e)
{
   if(e.Field.Name == "print")
   {
      object value = recordPositions[e.Record.Id];
      if(value != null)
         e.Value = value;
   }
}
void gridGroupingControl1_QueryRecordMeetsFilterCriteria(object sender, QueryRecordMeetsFilterCriteriaEventArgs e)
{
   if(restrict)
   {
      e.Handled = true;
      e.Result = (bool)recordPositions[e.Record.Id];
   }
}
//Private method used for filtering Top-so-many and bottom-so-many values 
private void SetPositionInFilter()
{
   foreach (GridRecord rec in this.gridGroupingControl1.Table.Records)
   {
      int pos = -1;
      if(rec.ParentDetails != null && rec.ParentDetails.FilteredRecords != null)
      {
         pos = rec.ParentDetails.FilteredRecords.IndexOf(rec);
      }
      // Filters the Top and bottom 2 records.
      bool val = (pos > -1) && (pos < 2 || pos >= rec.ParentDetails.FilteredRecords.Count - 2);
      if(recordPositions.ContainsKey(rec.Id))
      {
         recordPositions[rec.Id] = val;
      }
      else
      {
         recordPositions.Add(rec.Id, val);
      }
   }
   restrict = true;
}

'events triggered on the form load.
Private Me.gridGroupingControl1.TableDescriptor.QueryValue += New FieldValueEventHandler(AddressOf unboundField_QueryValue)
Private Me.gridGroupingControl1.QueryRecordMeetsFilterCriteria += AddressOf gridGroupingControl1_QueryRecordMeetsFilterCriteria
Private Me.gridGroupingControl1.FilterBarSelectedItemChanged += AddressOf gridGroupingControl1_FilterBarSelectedItemChanged
‘Gets the filterbar selected text. 
Private Sub gridGroupingControl1_FilterBarSelectedItemChanged(ByVal sender As Object, ByVal e As FilterBarSelectedItemChangedEventArgs)
   If searchtext <> e.SelectedText AndAlso searchtext IsNot Nothing Then
      restrict = False
      SetPositionInFilter()
      searchtext = e.SelectedText
End Sub
'Gets the checkBox values in a hashtable.
Private Sub unboundField_QueryValue(ByVal sender As Object, ByVal e As FieldValueEventArgs)
   If e.Field.Name = "print" Then
      Dim value As Object = recordPositions(e.Record.Id)
      If value IsNot Nothing Then
         e.Value = value
      End If
   End If
End Sub
Private Sub gridGroupingControl1_QueryRecordMeetsFilterCriteria(ByVal sender As Object, ByVal e As QueryRecordMeetsFilterCriteriaEventArgs)
   If restrict Then
      e.Handled = True
      e.Result = CBool(recordPositions(e.Record.Id))
   End If
End Sub
'Private method used for filtering Top-so-many and bottom-so-many values 
Private Sub SetPositionInFilter()
   For Each rec As GridRecord In Me.gridGroupingControl1.Table.Records
       Dim pos As Integer = -1
       If rec.ParentDetails IsNot Nothing AndAlso rec.ParentDetails.FilteredRecords IsNot Nothing Then
          pos = rec.ParentDetails.FilteredRecords.IndexOf(rec)
       End If
       ‘Filtering Top and bottom 2 records.
       Dim val As Boolean = (pos > -1) AndAlso (pos < 2 OrElse pos >= rec.ParentDetails.FilteredRecords.Count - 2)
       If recordPositions.ContainsKey(rec.Id) Then
          recordPositions(rec.Id) = val
       Else
          recordPositions.Add(rec.Id, val)
       End If
   Next rec
   restrict = True
End Sub

Top and bottom two record value set as true on filtering