CODEWITHSUNDEEP
wpfbinding
Marcom
Marcom

Reputation: 4751

Set datacontext dependency property

I am trying to set datacontext of a control using the following code: 

public object GlobalContext
{
    set { this.SetValue(global.DataContext as DependencyProperty , value);  }
}

Where global is a control, in this case a stackpanel.

When I mouse over global.DataContext it says its a dependency property so I figured it should work, but I get the following error:

A 'Binding' cannot be set on the 'GlobalContext' property of type 'ResourceModuleAccessView'. A 'Binding' can only be set on a DependencyProperty of a DependencyObject.

Any way I can make this work?

Edit 1: In the user control I have: 

 <StackPanel x:Name="global" Orientation="Horizontal">

and in the places where I am trying to reuse the control: 

    <my:ResourceModuleAccessView  

        ControlName="Usage Monitoring"
        GlobalContext="{Binding Path=moduleAccess.GlobalAccess[ResourceModule.UsageMonitoring]}"          
          GroupContext="{Binding Path=moduleAccess.Items[ResourceModule.UsageMonitoring]}" />

Upvotes: 0

Views: 1247

Answers (2)

aL3891
aL3891

Reputation: 6275

Your GlobalContext class must inheirit from DependencyObject if you are going to use it as a binding target or use the SetValue method. Also, you should pass the static DataContext*Property* from FrameworkElement to setValue, thats the actual dependecy property object, you're passing the datacontext object twice. In other words the call should be

SetValue(FrameworkElement.DataContextProperty,value);

i suspect there is something else wrong than this code though, can you post your xaml?

-edit-

Thanks for adding the code, since you're binding To your class (you class is a binding target as opposed to a binding source), you must make it a DependecyObject and make your GlobalContext a DependecyProperty.

Also note that when the binding system sets a dependecy property, it doesnt use the regular clr property, it uses the DependencyProperty object directly. This means that if you want to register a call back for when the property is changed, you must do that in the call to Register when you create the DependecyProperty

Upvotes: 2

ColinE
ColinE

Reputation: 70160

The DataContext property, which is defined on FrameworkElement is a dependency property, i.e. it is a property that is 'backed' by the WPF dependency property framework. However the type of this property is object. The fact that it is a dependency property tells you how it is stored, not the type of the data stored within it.

Upvotes: 0

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