Hi, I would like to implement some functionality that a normal .NET Dataset offers in a esCollection...

The functionality would be creating custom columns which hold calculated values over the collection. After this i need to be able to create a esEntityCollectionView(of EntityColletion) over it... Is this possible with the EntityCollection? Here is a code snippet of how I would accomplish this with a dataset. I really have NO idea of how to do this with the esCollection....

Dim ddc1 As DataColumn = New DataColumn()
ddc1.ColumnName = "maxWorkStop"
ddc1.DataType = GetType(System.DateTime)
ddc1.Expression = "max(child(workitems).Stop)"

Dim ddc2 As DataColumn = New DataColumn()
ddc2.ColumnName = "minWorkStart"
ddc2.DataType = GetType(System.DateTime)
ddc2.Expression = "min(child(workitems).Start)"

Dim ddc3 As DataColumn = New DataColumn()
ddc3.ColumnName = "maxTaskStop"
ddc3.DataType = GetType(System.DateTime)
ddc3.Expression = "max(Child(subtasks).maxWorkStop)"

Dim ddc4 As DataColumn = New DataColumn()
ddc4.ColumnName = "minTaskStart"
ddc4.DataType = GetType(System.DateTime)
ddc4.Expression = "min(Child(subtasks).minWorkStart)"

dataSet1.Tables("Task").Columns.Add(ddc1)
dataSet1.Tables("Task").Columns.Add(ddc2)
dataSet1.Tables("Task").Columns.Add(ddc3)
dataSet1.Tables("Task").Columns.Add(ddc4)

Okay, this is a wide topic. First let me say that EntitySpaces will not work with DataSets or create collections over mulitple DataTables (this is by design and I could go into my diatribe as to why but will spare you from it) he he. Here is a post in our FAQ forum about extended properties.

Extended Properties

Also, there is a protected member that you can access from your "Custom" classes called "Table", this is the DataTable, you can add columns and such with expression that way too. You can even add those expression columns and expose them as Extended properties.

Is it still possible to get an aggregate value in a column when the parent/child relationship is handled in a relation to the table itself (through a parentId field)?

So if I have three fields:

1. FieldId
2. ParentId
3. DateField

Can I then get the maximum dateField value where the ParentId is the current FieldId? This isn't really ES anymore is it?

Am I doing something wrong here? I call the AddAggregateColumns function before the collection is loaded...

'===============================================================================
'                     EntitySpaces(TM) by EntitySpaces, LLC
'                 A New 2.0 Architecture for the .NET Framework
'                          http://www.entityspaces.net
'===============================================================================
'                       EntitySpaces Version # 2008.1.0623.0
'                       MyGeneration Version # 1.2.0.7
'                       Date Generated       : 13-8-2008 13:01:07
'-------------------------------------------------------------------------------

Imports System
Imports System.Collections.Generic
Imports System.Text
Imports System.Data

Imports EntitySpaces.Interfaces

Namespace BLL

	Partial Public Class EpPlan 
        Inherits esEpPlan

        Protected Overrides Function GetLocalBindingProperties() As System.Collections.Generic.List(Of EntitySpaces.Core.esPropertyDescriptor)
            Dim props As New List(Of EntitySpaces.Core.esPropertyDescriptor)
            props.Add(New EntitySpaces.Core.esPropertyDescriptor(Me, "MinStart", GetType(DateTime)))
            props.Add(New EntitySpaces.Core.esPropertyDescriptor(Me, "MaxFinish", GetType(DateTime)))
            Return props
            'Return MyBase.GetLocalBindingProperties()
        End Function

        Public Property MinStart() As DateTime
            Get
                Return CType(Me.GetColumn("Min_Start"), DateTime)
            End Get
            Set(ByVal value As DateTime)
                Me.SetColumn("Min_Start", value)
            End Set
        End Property

        Public Property MaxFinish() As DateTime
            Get
                Return CType(Me.GetColumn("Max_Finish"), DateTime)
            End Get
            Set(ByVal value As DateTime)
                Me.SetColumn("Max_Finish", value)
            End Set
        End Property

        Public Sub AddAggregateColumns()
            Dim max As New DataColumn
            Dim min As New DataColumn
            max.ColumnName = "Max_Finish"
            max.Expression = "Max(Finish_Date)"

            min.ColumnName = "Min_Start"
            min.Expression = "Min(Start_Date)"

            Me.Table.Columns.Add(min)
            Me.Table.Columns.Add(max)
        End Sub
	End Class

End Namespace

In my supplied example, if everything is databound, when you change a value in the 'Child' data, the aggregate column is also automatically updated.

Are the fields created by the query API also updated dynamically without a roundtrip to the database?

Edit:

If I add the aggregate columns after the collection is loaded, then I receive an Null reference exception. It seems that the Table property in the EpPlan class is Null... So adding any columns is not possible...

 The addAggregateColumns function loops through the Entities in the collection, and calls AddAggregateColumns for every entity. The code for that is a few posts earlier...

Does work (well, at least adding the columns does LOL):

Dim coll as new EpPlanCollection
coll.addAggregateColumns()
coll.LoadAll()

Doesn't work:

Dim coll as new EpPlanCollection
coll.LoadAll()
coll.addAggregateColumns()

Ok let me rephrase as to what I'm trying to accomplish with a small example:

The dataset looks like this:

| ID | PARENT_ID | START_DATE | FINISH_DATE |
|  1 |      NULL |       NULL |        NULL |
|  2 |         1 | 01-01-2008 |  01-10-2008 |
|  3 |         1 | 01-10-2008 |  01-15-2008 |
|  4 |         1 | 01-15-2008 |  01-21-2008 |
|  5 |      NULL |       NULL |        NULL |
|  6 |         5 | 02-01-2008 |  02-09-2008 |
|  7 |         5 | 02-09-2008 |  02-12-2008 |
|  8 |         5 | 02-12-2008 |  02-17-2008 |
|  9 |         5 | 02-17-2008 |  02-25-2008 |
| 10 |      NULL |       NULL |        NULL |
| 11 |        10 | 03-01-2008 |  03-10-2008 |
| 12 |        10 | 03-10-2008 |  03-11-2008 |
| 13 |        10 | 03-11-2008 |  03-12-2008 |
| 14 |        10 | 03-12-2008 |  03-13-2008 |

I need to add two columns:

1. Min_Start
2. Max_Finish

These columns should get the Min(START_DATE) and Max(FINISH_DATE) of the rows where the PARENT_ID is equal to the ID of the 'current-row'. This is the dataset that should be returned:

| ID | PARENT_ID | START_DATE | FINISH_DATE |  MIN_START | MAX_FINISH |
|  1 |      NULL |       NULL |        NULL | 01-01-2008 | 01-21-2008 |
|  2 |         1 | 01-01-2008 |  01-10-2008 |       NULL |       NULL |
|  3 |         1 | 01-10-2008 |  01-15-2008 |       NULL |       NULL |
|  4 |         1 | 01-15-2008 |  01-21-2008 |       NULL |       NULL |
|  5 |      NULL |       NULL |        NULL | 02-01-2008 | 02-25-2008 |
|  6 |         5 | 02-01-2008 |  02-09-2008 |       NULL |       NULL |
|  7 |         5 | 02-09-2008 |  02-12-2008 |       NULL |       NULL |
|  8 |         5 | 02-12-2008 |  02-17-2008 |       NULL |       NULL |
|  9 |         5 | 02-17-2008 |  02-25-2008 |       NULL |       NULL |
| 10 |      NULL |       NULL |        NULL | 03-01-2008 | 03-13-2008 |
| 11 |        10 | 03-01-2008 |  03-10-2008 |       NULL |       NULL |
| 12 |        10 | 03-10-2008 |  03-11-2008 |       NULL |       NULL |
| 13 |        10 | 03-11-2008 |  03-12-2008 |       NULL |       NULL |
| 14 |        10 | 03-12-2008 |  03-13-2008 |       NULL |       NULL |

Now here's the catch (i think):

When I change the FINISH_DATE value of Row 14 to 03-29-2008 (In a databound DataGridView), I need the MAX_FINISH of row 10 to be instantly changed to 03-29-2008 too...

I need it to be instantly changed. a re-query is not an option since this will affect performance dramatically...

toch bedankt ;-)