Develop Reference

WPF how to access other variable from same viewmodel?

To display items on Telerik:RadGridView usually I use DataContext="{Binding [someViewModel]}" and ItemSource="{Binding objectList, Mode=TwoWay}".
and for my column I'll access the objectfield. The overall picture will be something like below:
<telerik:RadGridView DataContext="{Binding [someViewModel]}"
ItemSource="{Binding objectList, Mode=TwoWay}">
<telerik:RadGridView.Columns>
<telerik:GridViewDataColumn>
<telerik:GridViewDataColumn.CellTemplate>
<DataTemplate>
<CheckBox IsEnabled="{Binding enabledVar}"
IsChecked="{Binding isChecked, Mode=Twoway}"
</DataTemplate>
</telerik:GridViewDataColumn.CellTemplate>
</telerik:GridViewDataColumn>
</telerik:RadGridView.Columns>
</telerik:RadGridView>
Imagine there will be 10 items in objectList. Each of the item in objectList will have a variable isChecked which to manipulate the checkbox IsChecked property.
I have another variable in the same viewmodel named enabledVar which to control the ten checkbox IsEnabled property. enabledVar is not part of the objectList but I couldn't get the value. May I know how to handle such case?
Updates:
I've found some new direction but not sure if it helps.
<CheckBox IsEnabled="{Binding enabledVar,
RelativeSource={RelativeSource Mode=FindAncestor,
AncestorType=telerik:RadGridView}}"
but then of course, still failed.
Any helps would be very much appreciated.

if using Ancestor you have to bind to DataContext
<CheckBox IsEnabled="{Binding Path=DataContext.enabledVar,
RelativeSource={RelativeSource Mode=FindAncestor,
AncestorType=telerik:RadGridView}}"
Another aproach could be to use element binding set name
<telerik:RadGridView x:Name="myGrid" ...
And then in the celltemplate bind to it
<CheckBox IsEnabled="{Binding Path=DataContext.enabledVar, ElementName=myGrid}"
Hope this helps.

The code suggested in Update will not work because GridViewDataColumn is not part of the Visual tree, and hence can not access DataContext.
You will have to make use of proxy data binding, like suggested here. You can get more examples by searching "wpf proxy databinding".

Bind to Parent Object Property with RelativeSource

I've built a WPF based Treeview with
Item
-Subitem
If Subitem is selected, I would like to display also Properties of Item.
<StackPanel Grid.Column="2" DataContext="{Binding ElementName=myTreeView, Path=SelectedItem}">
<TextBox Text="{Binding Path=Name, Mode=TwoWay}" />
<TextBox Text="{Binding RelativeSource={???} Path=Name, Mode=TwoWay}" />
</StackPanel>
I guess I need to use a RelativeSource statement, but not quite sure how to do so.

{Binding RelativeSource={RelativeSource AncestorType={x:Type typeOfAncestor}}, Path=Name, Mode=TwoWay}

JesseJames has given you the correct way to use RelativeSource but the best you will be able to do with RelativeSource is bind to the TreeViewItem itself, which is just the container for your data object i.e ViewModel, meaning you won't be able to access your data objects properties(easily).
I think in this case binding to the container object would break the View-ViewModel approach you are using. Your best bet would be to create a Parent object within your ViewModel and bind to that object. So that now each object in your collection has a reference to it's parent which can now be bound to directly.
<StackPanel Grid.Column="2" DataContext="{Binding ElementName=myTreeView, Path=SelectedItem}">
<TextBox Text="{Binding Path=Name, Mode=TwoWay}" />
<TextBox Text="{Binding Parent.Name}" />
</StackPanel>
Also note that the SelectedItem property returns your data object and not the container.

I looked at your code, try binding simply to Name. It appears that your data context should already be set to the TreeViewItem due to the following line: <StackPanel Grid.Column="2" DataContext="{Binding ElementName=myTreeView, Path=SelectedItem}">. The RelativeResource binding is probably looking further up the logical tree and that's why your binding is failing.

Combobox selections

I have this combobox which contains a data tempate with a checkbox and a textbox. All is working but I would like to make it a little bit easier to select a value. Right now I have to click on the chechbox to change the value of the check box. Now I would like to be able to just click on the item in the combobox which also should toggle the checkbox.
Is this possible? If yes then how?
Here is a picture of my solution right now
Here is the code for my combobox
<ComboBox Name="employeeComboBox" Margin="2,0,2,0"
ScrollViewer.CanContentScroll="False"
DataContext="{Binding EmployeesOverviewViewModel, Source={StaticResource ViewModelLocator}}"
ItemsSource="{Binding Employees}">
<ComboBox.ItemTemplate>
<DataTemplate>
<StackPanel Orientation="Horizontal">
<CheckBox IsChecked="{Binding Path=IsSelected}" Margin="2,0,2,2" VerticalAlignment="Center"/>
<TextBlock Text="{Binding Path=Name}" VerticalAlignment="Center"/>
</StackPanel>
</DataTemplate>
</ComboBox.ItemTemplate>
</ComboBox>

Change your DataTemplate to this:
<DataTemplate>
<CheckBox IsChecked="{Binding Path=IsSelected}"
Margin="2,0,2,2"
Content="{Binding Path=Name}"
VerticalAlignment="Center"/>
</DataTemplate>
and it should work.

Why don't you use the Content property on the CheckBox?
<CheckBox Content="Hello, World" />
This way, the checkbox would toggle even when you click on the text (content).
As for your specific case, you can bind Name to Content instead of creating a separate TextBlock for it, and it should work as you want it to.

Whats happning here is, Your Checkbox and text are two different entities, you need to make them one, by simply using checkbox's text property and binding it. that way whenever you click on text your checkbox gets selected.

WPF Multiple ItemSources?

Is it possible to have multiple ItemSources for a single control?
Given the code below:
<ComboBox Margin="137,101,169,183" ItemsSource="{Binding collection}" SnapsToDevicePixels="True"
<ComboBox.ItemTemplate>
<DataTemplate>
<StackPanel Orientation="Horizontal">
<CheckBox Command="{Binding CheckCommand}" IsChecked="{Binding IsChecked}" Content="{Binding Name}"/>
<TextBlock Text="" />
</StackPanel>
</DataTemplate>
</ComboBox.ItemTemplate>
</ComboBox>
The TextBlock within the ComboBox DataTemplate requires data from another property within the VM than that of the ComboBox. How can this be achieved?
Thanks.

You can use RelativeSource-FindAncestor to reach up the visual tree and grab a different DataContext.
For example (assuming the command is what you want):
Command=”{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type ComboBox}}, Path=CheckCommand}”
This should also serve as a good resource.
Edit: Typo and resources.

If i remember correctly, DataTemplates run within their own scope and cannot directly use ElementNames defined outside the DataTemplate. You could however get around it by using StaticResource and referring to that directly from TextBlock inside the template.
I haven't tried Ragepotatos's approach to go outside DataTemplate scope but would love to know if that works out for you too.

How to read the checkbox value in RowHeaderTemplate?

<my:DataGrid.RowHeaderTemplate>
<DataTemplate>
<Grid>
<CheckBox Name="dgChkSelect" Checked="dgChkSelect_Checked" Unchecked="dgChkSelect_Unchecked" Tag="{Binding}" />
<!--IsChecked="{Binding Path=IsSelected,Mode=TwoWay,RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type my:DataGridRow}}}"-->
</Grid>
</DataTemplate>
</my:DataGrid.RowHeaderTemplate>
Hi all, I want to loop through the datagrid data to retrieve those records has been checked.
Anyone know how to do this?

You were in the right path add IsChecked="{Binding Path=IsSelected, Mode=TwoWay}". Dont have the rest of the relative source stuff. Datagrid's itemsource will be searched for the property IsSelected; Make sure you have a property. On a separate note why aren't you using
DataGridCheckBoxColumn.