update-checkbox-state-programmatically-treeview-xamarin

This repository demonstrates how to update the checkbox state of nodes programmatically in the Syncfusion Xamarin.Forms TreeView control. The sample shows how to check or uncheck TreeView nodes in response to application logic, user actions outside the TreeView, or ViewModel changes. It covers how to manipulate the checked state directly from code.

Sample

Behaviour

public class TreeViewBehavior : Behavior<SfTreeView>
{
    SfTreeView TreeView;
 
   protected override void OnAttachedTo(SfTreeView bindable)
    {
        base.OnAttachedTo(bindable);
 
        TreeView = bindable;
        TreeView.Loaded += TreeView_Loaded;
    }
 
    private void TreeView_Loaded(object sender, TreeViewLoadedEventArgs e)
    {
        UpdateCheckBoxState();
        TreeView.CheckBoxMode = CheckBoxMode.Recursive;
    }
 
    private void UpdateCheckBoxState()
    {
        var checkedNodes = TreeView.GetCheckedNodes();
        foreach (var node in checkedNodes)
        {
            if (node.ParentNode == null && node.HasChildNodes)
            {
                //Update child nodes based on parent's checked state.
                SetChildChecked(node);
            }
 
            else
            {
                //Update parent node based on child's checked state.
                SetParentChecked(node);
            }
        }
    }
 
    private void SetChildChecked(TreeViewNode node)
    {
        foreach (var child in node.ChildNodes)
        {
            child.IsChecked = true;
            if (child.HasChildNodes)
            {
                SetChildChecked(child);
            }
        }
    }
 
    private void SetParentChecked(TreeViewNode node)
    {
        if (node.ParentNode == null) return;
 
        if (node.ParentNode.ChildNodes.All(x => x.IsChecked == true))
            node.ParentNode.IsChecked = true;
 
        else node.ParentNode.IsChecked = null;
 
        if(node.ParentNode != null)
        {
            SetParentChecked(node.ParentNode);
        }
    }
}

Requirements to run the demo

To run the demo, refer to System Requirements for Xamarin

Troubleshooting

Path too long exception

If you are facing path too long exception when building this example project, close Visual Studio and rename the repository to short and build the project.