ItemsSource vs DataContext in the binding case

[Tai]

Hi

My main question is about binding case in the scene that we have multiple sources for a control(a combobox inside a datagrid)(or having both datacontext and itemssource). Then how can we know which source the binding will use? (any syntax to clarify that)

Assuming a datagrid has an itemssource="List of Players" datacontext="Manager"
 , and has a combobox as a kind of column. We also assume that each player has an Inventory property which is a collection type.

 then inside the <datagrid.columns> ,
1. The current source of each column(for binding) is a Player(this is how i understand it so far). We can only bind to the property of the player not to the property of the datacontext "manager". There is no way to bind to the property of the "Manager". Am i correct?
        2. However, if we move to the combobox columns, then assume i will let combobox's itemssource ='player 's inventory', then the current source for comboboxItem will be each item in the inventory. And if i use the binding, it can only bind to the property of those items.
However, sometimes i see the code that we can also bind to the property of the player inside the combobox's property especially Selected Value and SelectedItem. I am a little confused here
can you help me?

thank you

              

[Pavel Pavlov]

Hi Tai,

Here are some clarifications :

When you have a DataContext  for RadGridView ... it will not be the DataContext for the combo .
At cell level the DataContext is the business object relevant to the row.

So for example :
Lets imagine the RadGridView is bound to a collection of Employee objects.
If you use ItemsSource ={Binding Countries} ,

RadGridView will  search for a Countries property on the Employee object.

Now lets say you need to bind to a collection that is not in the Employee object , but in the DataContext itself.

In such case you will need to expose the collection as a static resource  and use syntax like :
ItemsSource = {Binding Countries , Source={StaticResource ....}

In case all this sounds obscure, just let me know your business scenario , and I will try to provide a small sample for you.


Kind regards,
Pavel Pavlov
the Telerik team

[Mark]

Hi,
I am completely new to silverlight, so forgive me if I'm missing something obvious.   We have a similar scenario.   I have a telerik radgridview to which I am dynamically adding data using a wpf service.  I have added a comboboxcolumn in the code which goes to get the relavant data from another web service function call.   The problem I have at the moment is I can't see how to programatically select the correct item in the comboboxcolumn.   Currently the data come into the combobox, but the combobox does not show up at all until I select the row, and then the combobox cell.   Then I have to click the dropdown arrow and I find the selections.   what I want is for the combobox to show up automatically with the correctly selected item in the combobox.  

We are using VS 2010 and Silverlight 3.  Although we would like to use Silverlight 4, our corporate policy from "the mother ship" will not able to support it at this time, so we can only use SL 3.

Since I am quite new to silverlight, I'm hoping to get advice and examples on best practices.  Perhaps I went down the wrong path with doing this dynamically in the codebehind, but one of my objectives is to create generic solutions to the degree possible, and usually I get that through code.   However, if XAML based configuration is much easier (from the examples I've seen XAML seems prefered) then I would want to know that as well.  Anyway, thanks in advance for the help!

The dbml file has two tables: 

REF_TestTable (which has a foreign key REF_Facility_LDS_LineID that links to the Primary Key ID field of the next table)
REF_Facility_LDS_Line

Here is the relavant code for the project:

Main Page Code Behind

Imports Telerik.Windows.Controls

Imports Telerik.Windows.Controls.GridView

Imports System.Windows.Data

  

Partial Public Class MainPage

    Inherits UserControl

  

    Public Sub New()

        InitializeComponent()

        AddHandler Me.RadGridView1.CellEditEnded, AddressOf radGridView_CellEditEnded

    End Sub

  

    Private Sub webService_GetRowsCompleted(ByVal sender As Object, ByVal e As ServiceReference1.GetRowsCompletedEventArgs)

        Me.RadGridView1.ItemsSource = e.Result

        DirectCast(Me.RadGridView1.Columns("EntryDate"), GridViewDataColumn).DataFormatString = "{0:MM/dd/yyyy}"

        Dim webService As New ServiceReference1.Service1Client

        AddHandler webService.GetREF_Facility_LDS_LineCompleted, AddressOf webService_GetREF_Facility_LDS_LineCompleted

        webService.GetREF_Facility_LDS_LineAsync()

    End Sub

  

    Private Sub webService_GetREF_Facility_LDS_LineCompleted(ByVal sender As Object, ByVal e As ServiceReference1.GetREF_Facility_LDS_LineCompletedEventArgs)

        Try

            Dim column As New Telerik.Windows.Controls.GridViewComboBoxColumn

  

            column.ItemsSource = e.Result

            column.Header = "LDS"

            column.SelectedValueMemberPath = "ID"

            column.DisplayMemberPath = "LubeDistributionSystem"

            column.UniqueName = "cboLDS"

                
'-- we need the row in the combobox to be selected for the item that corresponds to the radgridview column REF_Facility_LDS_LineID

            
            Me.RadGridView1.Columns.Insert(4, column)

  

        Catch ex As Exception

  

        End Try

    End Sub

  

    Private Sub GetData_Click(ByVal sender As System.Object, ByVal e As System.Windows.RoutedEventArgs) Handles cmdGetData.Click

        Dim webService As New ServiceReference1.Service1Client

  

        AddHandler webService.GetRowsCompleted, AddressOf webService_GetRowsCompleted

  

        webService.GetRowsAsync()

    End Sub

  

    Private Sub AddNew_Click(ByVal sender As System.Object, ByVal e As System.Windows.RoutedEventArgs) Handles cmdAddNew.Click

        Dim webService As New ServiceReference1.Service1Client

        webService.InsertDataAsync(Me.txtName.Text, Me.txtServerName.Text)

        AddHandler webService.GetRowsCompleted, AddressOf webService_GetRowsCompleted

        webService.GetRowsAsync()

    End Sub

  

    Private Sub radGridView_CellEditEnded(ByVal sender As Object, ByVal e As Telerik.Windows.Controls.GridViewCellEditEndedEventArgs)

        If e.EditAction = Telerik.Windows.Controls.GridView.GridViewEditAction.Cancel Then

            Exit Sub

        End If

  

        If e.EditAction = Telerik.Windows.Controls.GridView.GridViewEditAction.Commit Then

  

            Dim webService As New ServiceReference1.Service1Client

            Dim ID As Integer

            Dim Name As String

            Dim ServerName As String

            Dim Category As String

            Dim Active As Boolean

            Dim EntryDate As Date

            Dim REF_Facility_LDS_LineID As String

  

            ID = RadGridView1.SelectedItems.Item(0).ID

            Name = RadGridView1.SelectedItems.Item(0).Name

            ServerName = RadGridView1.SelectedItems.Item(0).ServerName

            Category = RadGridView1.SelectedItems.Item(0).Category

            Active = RadGridView1.SelectedItems.Item(0).Active

            EntryDate = RadGridView1.SelectedItems.Item(0).EntryDate

            REF_Facility_LDS_LineID = RadGridView1.SelectedItems.Item(0).REF_Facility_LDS_LineID

  

            webService.UpdateDataAsync(ID, Name, ServerName, Category, Active, EntryDate, REF_Facility_LDS_LineID)

  

        End If

  

    End Sub

  

End Class

Main Page XAML

<UserControl xmlns:my2="clr-namespace:Telerik.Windows.Controls;assembly=Telerik.Windows.Controls.Input"  x:Class="Silverlight_Test3.MainPage"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d"
    d:DesignHeight="697" d:DesignWidth="812"
    xmlns:my="clr-namespace:System.Windows.Controls;assembly=System.Windows.Controls.Data" xmlns:my1="http://schemas.telerik.com/2008/xaml/presentation" xmlns:telerikGridView="clr-namespace:Telerik.Windows.Controls;assembly=Telerik.Windows.Controls.GridView" xmlns:dataInput="clr-namespace:System.Windows.Controls;assembly=System.Windows.Controls.Data.Input">

    <Grid x:Name="LayoutRoot" Background="AliceBlue" Height="623" Width="738">
        <TextBox Height="23"
                 HorizontalAlignment="Left"
                 Margin="64,41,0,0"
                 Name="txtName"
                 VerticalAlignment="Top"
                 Width="147" />
        <TextBox Height="23" HorizontalAlignment="Left" Margin="239,41,0,0" Name="txtServerName" VerticalAlignment="Top" Width="147" />
        <Button Content="Get Data" Height="38" HorizontalAlignment="Left" Margin="576,41,0,0" Name="cmdGetData" VerticalAlignment="Top" Width="147" />
        <Button Content="Add New" Height="38" HorizontalAlignment="Left" Margin="415,41,0,0" Name="cmdAddNew" VerticalAlignment="Top" Width="139" />
        <dataInput:Label Content="Telerik Grid" Height="18" HorizontalAlignment="Left" Margin="12,80,0,0" Name="lblTelerikGrid" VerticalAlignment="Top" Width="242" />
        <dataInput:Label Content="Name" Height="18" HorizontalAlignment="Left" Margin="64,12,0,0" Name="lblName" VerticalAlignment="Top" Width="147" />
        <dataInput:Label Content="Server Name" Height="18" HorizontalAlignment="Left" Margin="239,12,0,0" Name="lblServerName" VerticalAlignment="Top" Width="147" />
        <telerikGridView:RadGridView
            AutoGenerateColumns="True"
            HorizontalAlignment="Left"
            Margin="12,104,0,0"
            Name="RadGridView1"
            VerticalAlignment="Top"
            Width="710"
            Height="493"
            SelectionMode="Extended"
            DataContext="{Binding}">
        </telerikGridView:RadGridView>
    </Grid>
</UserControl>

Web Service:

Imports System.ServiceModel
Imports System.ServiceModel.Activation
Imports System.Collections.Generic
Imports System.Text

<ServiceContract(Namespace:="")>
<AspNetCompatibilityRequirements(RequirementsMode:=AspNetCompatibilityRequirementsMode.Allowed)>
Public Class Service1

    <OperationContract()> _
    Public Function GetRows() As List(Of REF_TestTable)

        Dim db As New DataClasses1DataContext()

        Dim selected_rows = From rows In db.REF_TestTables

        Return selected_rows.ToList()

    End Function

    <OperationContract()> _
    Public Function GetREF_Facility_LDS_Line() As List(Of REF_Facility_LDS_Line)

        Dim db As New DataClasses1DataContext()

        Dim selected_rows = From rows In db.REF_Facility_LDS_Lines

        Return selected_rows.ToList()

    End Function

    <OperationContract()> _
    Public Sub InsertData(ByVal Name As String, ByVal ServerName As String)
        Dim db As New DataClasses1DataContext()

        Dim row As New REF_TestTable() With { _
         .Name = Name, _
         .ServerName = ServerName, _
         .Category = "P", _
         .Active = True, _
         .EntryDate = Today.ToShortDateString, _
         .REF_Facility_LDS_LineID = "1"
        }

        ' Add the new object to the collection.
        db.REF_TestTables.InsertOnSubmit(row)

        ' Submit the change to the database.
        db.SubmitChanges()
    End Sub

    <OperationContract()> _
    Public Sub UpdateData(ByVal ID As Integer, ByVal Name As String, ByVal ServerName As String, ByVal category As String, ByVal Active As Boolean, ByVal EntryDate As Date, ByVal REF_Facility_LDS_LineID As String)
        Dim db As New DataClasses1DataContext()

        Dim rowQuery = From REF_TestTable In db.REF_TestTables Where REF_TestTable.ID = ID
                       Select REF_TestTable

        For Each REF_TestTable As REF_TestTable In rowQuery
            REF_TestTable.Name = Name
            REF_TestTable.ServerName = ServerName
            REF_TestTable.Category = category
            REF_TestTable.Active = Active
            REF_TestTable.EntryDate = EntryDate.ToShortDateString
            REF_TestTable.REF_Facility_LDS_LineID = REF_Facility_LDS_LineID
        Next

        ' Submit the change to the database.
        db.SubmitChanges()
    End Sub

End Class

[Pavel Pavlov]

Hello Mark,

From the code pasted  , I can see that one of the things preventing the combo column to behave is the
missing setting of the DataMemberBinding .

Please set the DataMemberBinding  of the ComboBoxColumn  and there is a great chance for things start working better.

Greetings,
Pavel Pavlov
the Telerik team

[Mark]

Hi,
Thank you for the information about the DataBindingMember.  I was in the process of trying to figure out how to use it.  In my scenario where I am tyring to do this in the code behind, and with the data as I presented it, would you be so kind as to show me an example.  I tried a number of attempts to figure it out, but could not get it to work.   The combobox should have as it's selected item the related REF_Facility_LDS_LineID from the RadDataGrid.

[Pavel Pavlov]

Hello Mark,

Since I do not have your database here , I will give a sample with some imaginary tables.

Lets say we have the following data structure:
We have a table with Persons. Each person holds a foreign key to the countries table in a field called CountryID .
The countries table has two fields- ID and CountryName.

We need the RadGridView to display  the persons colelction so we set :
RadGridView.ItemsSource  to the persons collection.

We need a combo column , displaying  the country for each person ,
So we set up the column the following way
1. Set the ItemsSource of the combo column  to the Counties collection
2. Set DataMemberBinding = new Binding(){Path="CountryID"}
3. Set the DisplayMemberPath = "CountryName"
4. Set the SelectedValueMemberPath to "ID"

* In case you can not achieve the same with your data, just send me your database  or a simplified version of it , and I will prepare a small sample app for you  with your data structure.





Sincerely yours,
Pavel Pavlov
the Telerik team

[Mark]

Thanks for the reply.  I'm not sure how to apply that to my scenario.   Where would I put this:  

2. Set DataMemberBinding = new Binding(){Path="CountryID"}

??

could you provide a code example that corresponds to what I've done already so that I know how to integrate your advice?  I tried several things and none of them worked.   Thank you.

Mark

[Pavel Pavlov]

Hello Mark,

I would gladly provide a working sample project . Please let me know the structure of the relevant tables and fields in your db. + field names and data types , so I can create the sample applicable to your case.
I will need info about the primary table used as ItemsSource for the RadGridView  and the foreign table containing the ItemsSource for the combo .

I was giving example with imaginary data as I do not know the structure of your DB .

If you paste me the table names and the fields relevant to the problem , I can create here a small mock of the DB and build a working project/sample over it.

Greetings,
Pavel Pavlov
the Telerik team

[Mark]

SET ANSI_NULLS ON
GO

SET QUOTED_IDENTIFIER ON
GO

SET ANSI_PADDING ON
GO

CREATE TABLE [dbo].[REF_TestTable](
    [ID] [bigint] IDENTITY(1,1) NOT NULL,
    [Name] [varchar](50) NULL,
    [ServerName] [varchar](50) NULL,
    [Category] [varchar](1) NULL,
    [Active] [bit] NULL,
    [EntryDate] [date] NULL,
    [REF_Facility_LDS_LineID] [bigint] NULL,
    [Comments] [text] NULL,
    [Information] [text] NULL,
    [TestField1] [text] NULL,
    [TestField2] [text] NULL,
 CONSTRAINT [PK_REF_TestTable] PRIMARY KEY CLUSTERED
(
    [ID] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
) ON [PRIMARY] TEXTIMAGE_ON [PRIMARY]

GO

SET ANSI_PADDING OFF
GO

ALTER TABLE [dbo].[REF_TestTable]  WITH CHECK ADD  CONSTRAINT [FK_REF_TestTable_REF_Facility_LDS_Line] FOREIGN KEY([REF_Facility_LDS_LineID])
REFERENCES [dbo].[REF_Facility_LDS_Line] ([ID])
GO

ALTER TABLE [dbo].[REF_TestTable] CHECK CONSTRAINT [FK_REF_TestTable_REF_Facility_LDS_Line]
GO

ALTER TABLE [dbo].[REF_TestTable] ADD  CONSTRAINT [DF_REF_TestTable_EntryDate]  DEFAULT (getdate()) FOR [EntryDate]
GO

/****** Object:  Table [dbo].[REF_Facility_LDS_Line]    Script Date: 11/04/2010 13:01:01 ******/
SET ANSI_NULLS ON
GO

SET QUOTED_IDENTIFIER ON
GO

SET ANSI_PADDING ON
GO

CREATE TABLE [dbo].[REF_Facility_LDS_Line](
    [ID] [bigint] IDENTITY(1,1) NOT NULL,
    [REF_SAM_FacilityID] [int] NULL,
    [LubeDistributionSystem] [varchar](50) NULL,
    [Line] [varchar](50) NULL,
    [EntryDate] [date] NULL,
 CONSTRAINT [PK_REF_Facility_LDS_Line] PRIMARY KEY CLUSTERED
(
    [ID] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
) ON [PRIMARY]

GO

SET ANSI_PADDING OFF
GO

ALTER TABLE [dbo].[REF_Facility_LDS_Line]  WITH CHECK ADD  CONSTRAINT [FK_REF_Facility_LDS_Line_REF_SAM_Facility1] FOREIGN KEY([REF_SAM_FacilityID])
REFERENCES [dbo].[REF_SAM_Facility] ([ID])
GO

ALTER TABLE [dbo].[REF_Facility_LDS_Line] CHECK CONSTRAINT [FK_REF_Facility_LDS_Line_REF_SAM_Facility1]
GO

ALTER TABLE [dbo].[REF_Facility_LDS_Line] ADD  CONSTRAINT [DF_REF_Facility_LDS_Line_EntryDate]  DEFAULT (getdate()) FOR [EntryDate]
GO

Great thanks a lot!   Here are the two tables I'm working with.  You can find the source code I'm working with in my original post.  Much obliged!

Mark

[Pavel Pavlov]

Hello Mark,

I am attaching a sample with RadGridView set up according to the field names in your DB .

For simplicity and to avoid setup and sending of DB , I am using a small mockup classes that replicate the structure of your DB tables.

I have replaced the following VB code :

Dim column As New Telerik.Windows.Controls.GridViewComboBoxColumn

            column.ItemsSource = e.Result
            column.Header = "LDS"
            column.SelectedValueMemberPath = "ID"
            column.DisplayMemberPath = "LubeDistributionSystem"
            column.UniqueName = "cboLDS"

with the respective settings in XAML  ( see the XAML in MainPage.xaml.vb) .
the line column.ItemsSource = e.result  is replaced with :

CType(Me.RadGridView1.Columns("MyComboColumn"), GridViewComboBoxColumn).ItemsSource = GetSourceForComboColumn()

To see this in action please run the app and press the GetData button.

Copying the XAML to your project and setting the items source as demonstrated should do trick for your project.


Kind regards,
Pavel Pavlov
the Telerik team