how to access all contols on a page and select a few based upon certain condition and changing their properties.

Question

on a page out of many controls like text boxes, text blocks, buttons i want all of these not enabled on page load event except a few selected one for instance a back button. i did it the following way.

this.IsEnabled = false;
this.backButton.IsEnabled = true;

after disabling all controls it is not possible to enable a particular one.

interestingly if i use it this way.

 this.backButton.IsEnabled = false;
 this.IsEnabled = true;

in this case the back button does not get enabled again.

please suggest me a way out it seems that isenabled one property once changed can not be changed again in the same event procedure.

i also tried to search how to loop through all the controls but it didn't worked.

Answer 1

Hi Samul,

The elements in XAML are organized as a tree (a so called Visual Tree). In order to traverse the tree you need to use a recursive procedure.

The following code disables all controls on the page except one provided as a parameter:

DisableElements(this, "BackButtonName");

// ...

public void DisableElements(DependencyObject root, string doNotDisableControlName)
{
    for (int i = 0; i < VisualTreeHelper.GetChildrenCount(root); i++)
    {
        DependencyObject child = VisualTreeHelper.GetChild(root, i);

        if (child != null)
        {
            Control ctrl = child as Control;
            if (ctrl != null)
            {
                if (ctrl.Name != doNotDisableControlName)
                    ctrl.IsEnabled = false;
            }

            if (VisualTreeHelper.GetChildrenCount(child) > 0)
                DisableElements(child, doNotDisableControlName);
        }
    }
}

Leszek

---

My Apps

Answer 2

thanks i used it but after using it i am not able to enable back my controls.

i used this.isenabled = true

on click event of edit button so that a user can edit the data.

i also tried to do enable by the way you showed me to disable the controls.

so now also tell me how to solve this new problem coming. it should not come but i don't know why it is happening

i debugged the code and in the event that i am using to enable controls no child is returned.

you used the call and in that since grid being at i = 0 and having more child get disabled. so i used the same code to enable as shown.

 public void EnableElements(DependencyObject root) 
        {
            for (int i = 0; i < VisualTreeHelper.GetChildrenCount(root); i++) 
            {
                DependencyObject child = VisualTreeHelper.GetChild(root, i);
               
                    Control ctrl = child as Control;
                    if (ctrl != null) 
                    {
                        ctrl.IsEnabled = true;
                        if (VisualTreeHelper.GetChildrenCount(child) > 0)
                            EnableElements(child);
                    }
                
            }
        }

the problem is

 DependencyObject child = VisualTreeHelper.GetChild(root, 0);

even this is returning the child correctly then also i can't enable it

Answer 3

finally i did it

here is the corrected code

public void EnableElements(DependencyObject root) 
        {
            for (int i = 0; i < VisualTreeHelper.GetChildrenCount(root); i++) 
            {
                DependencyObject child = VisualTreeHelper.GetChild(root,i);
                if (child != null)
                {
                    Control ctrl = child as Control;
                    if (ctrl != null)
                    {
                        ctrl.IsEnabled = true;
                    }
                    if (VisualTreeHelper.GetChildrenCount(child) > 0)
                        EnableElements(child);
                }
                        
                        
                
            }
        }