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RadTreeView.GetItemByPath fails with hierarchical data binding

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answered on 14 Apr 2010, 08:04 AM

treeviewcontainerbindingssearch.zip

Hi Bjorn Sundby,

I am not sure that I understand your scenario correctly. However, I prepared a sample project, demonstrating how you can search an item in the ItemsSource collection of the RadTreeView. When the targeted item is found, it is expanded, selected and checked. The RadTreeView ItemsSource collection is bound to an ObservableCollection using HierarchicalDataTemplate and it works as expected on our side.

Can you take a look at the project and let me know if it helps?

Best wishes,
Tina Stancheva
the Telerik team

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answered on 14 Apr 2010, 09:58 AM

Thank you for Your quick response.

I was able to find my problem based on Your working sample.
It turned out that the data source model requires an override for the ToString method to let the TreeView know the name of the node.
So by adding the following code to my hierarchical data model item class; everything worked fine.

    
            public override string ToString()  
        
            {  
        
                return this.Name;  
        
            }

B.Sundby

answered on 14 Jul 2010, 09:20 PM

Hello Tina,

I have downloaded and run the project you attached in April, and I am able to use it successfully, however I can't seem to apply the same method to my project. GetItemByPath always returns null, for me. I can use ContainerFromItemRecursive, however that only works when the item has been rendered, visually.

I have a few questions for you:

Can you expand a bit on how the GetItemByPath method works?
Does my business object absolutely need to override it's ToString() method to output it's Name or Display property? In the example project, I was able to form paths with the object's names rather than their ToString() result and successfully find them in the tree. Can you explain how this works, exactly?
In order for GetItemByPath to return the object, is it necessary for the hierarchical business objects to be grouped into an ObservableCollection<>? Or will a List<> satisfy? I am aware that an ObservableCollection<> is needed to fire changes on the business objects up to the UI control, however is it necessary for use with GetItemByPath?

What settings on the RadTreeView might disable or disrupt the use of GetItemByPath? Is there some Style Property or Template Property that when altered my render the GetItemByPath method useless?
What steps must I take to ensure that GetItemByPath will find my business object?

Thanks in advance for answering my questions,
- Aaron

answered on 20 Jul 2010, 08:47 AM

treeviewcontainerbindingssearchmodified.zip

Hi Aaron,

When using the GetItemByPath() method with databound RadTreeView there are two approaches. The first approach is to override the ToString() method. Its value will be used as path segment. The second approach is to use the telerik:TextSearch.TextPath attached property to indicate which property will be used for matching.

I will try to explain the GetItemByPath() method in more details, hopefully that will enable you to find the cause for your issues.

The method takes the string that is passed through the path parameter and searches through the RadTreeView Items collection to find the first match. The matching mechanism splits the path into parts using the provided separator and compares it to the value of each TreeViewItem. Then if a RadTreeView item is a match, the method traverse the children of that item for a match to the next part of the path and so on.

However, when the RadTreeView is databound, the expression that is used to evaluate each RadTreeViewItem will return different values depending on whether a TextSearch.TextPath attached property is set and if it isn't - what does the ToString() method of the corresponding business classes return.
If the TextSearch.TextPath property isn't set and the ToString() method isn't overridden, the expression used to evaluate each RadTreeViewItem in the matching mechanism, will return the name of the corresponding business class, for example _289938_TreeViewContainerBindings.Company and will use that value to match it with the path parameter. Therefore if the passed path parameter is for example comp.Name, the GetItemByPath() method won't find any matches. And, if you pass comp.ToString()(=_289938_TreeViewContainerBindings.Company) as a path, the method will compare two identical strings at all times and won't return the corresponding to the path RadTreeViewItem, but the first match.

However, if the ToString() method is overridden, for example to return the Name property of the business class, the expression used to evaluate each RadTreeViewItem in the matching mechanism, will return also the Name property. Therefore as the path can be passed both comp.ToString() and comp.Name to the GetItemByPath() method to get the corresponding RadTreeViewItem.

In the second approach, the value of the TextSearch.TextPath property will be used as a path segment. I modified the example project to illustrate this approach so that you can see how it works and choose the best suited approach for you. Also, in the modified project all collections are of type List which actually doesn't affect the result of the GetItemByPath() method.

I hope this information will help you. However, if you need more info, please let me know and I will be more than happy to further assist you.

Best wishes,
Tina Stancheva
the Telerik team