Alternative solution of Treeview. bringlateral view method in WPF

Alternative solution of Treeview. bringlateral view method in WPF

Zhou yinhui

Treeview in WPF. the bringshortview () method is not so easy to use and will not work in many cases. Here is an alternative solution. Calling the selectitem () method can expand and present the specified item on the Treeview:

Public static class treeviewhelper

{

/// <Summary>

/// Expands all children of a Treeview

/// </Summary>

/// <Param name = "Treeview"> the Treeview whose children will be expanded </param>

Public static void expandall (this Treeview)

{

Expandsubcontainers (Treeview );

}

 

/// <Summary>

/// Expands all children of a Treeview or treeviewitem

/// </Summary>

/// <Param name = "parentcontainer"> the Treeview or treeviewitem containing the children to expand </param>

Private Static void expandsubcontainers (itemscontrol parentcontainer)

{

Foreach (Object item in parentcontainer. Items)

{

Treeviewitem currentcontainer = parentcontainer. itemcontainergenerator. containerfromitem (item) as treeviewitem;

If (currentcontainer! = NULL & currentcontainer. Items. Count> 0)

{

// Expand the item

Currentcontainer. isexpanded = true;

 

// If the item's children are not generated, they must be expanded

If (currentcontainer. itemcontainergenerator. status! = Generatorstatus. containersgenerated)

{

// Store the event handler in a variable so we can remove it (in the handler itself)

Eventhandler Eh = NULL;

Eh = new eventhandler (delegate

{

// Once the children have been generated, expand those children's children then remove the event handler

If (currentcontainer. itemcontainergenerator. Status = generatorstatus. containersgenerated)

{

Expandsubcontainers (currentcontainer );

Currentcontainer. itemcontainergenerator. statuschanged-= eh;

}

});

 

Currentcontainer. itemcontainergenerator. statuschanged + = eh;

}

Else // otherwise the children have already been generated, so we can now expand those children

{

Expandsubcontainers (currentcontainer );

}

}

}

}

 

/// <Summary>

/// Searches a Treeview for the provided object and selects it if found

/// </Summary>

/// <Param name = "Treeview"> the Treeview containing the item </param>

/// <Param name = "item"> the item to search and select </param>

Public static void selectitem (this Treeview, object item)

{

Expandandselectitem (Treeview, item );

}

 

/// <Summary>

/// Finds the provided object in an itemscontrol's children and selects it

/// </Summary>

/// <Param name = "parentcontainer"> the parent container whose children will be searched for the selected item </param>

/// <Param name = "itemtoselect"> the item to select </param>

/// <Returns> true if the item is found and selected, false otherwise </returns>

Private Static bool expandandselectitem (itemscontrol parentcontainer, object itemtoselect)

{

// Check all items at the current level

Foreach (Object item in parentcontainer. Items)

{

Treeviewitem currentcontainer = parentcontainer. itemcontainergenerator. containerfromitem (item) as treeviewitem;

 

// If the data item matches the item we want to select, set the corresponding

// Treeviewitem isselected to true

If (item = itemtoselect & currentcontainer! = NULL)

{

Currentcontainer. isselected = true;

Currentcontainer. bring1_view ();

Currentcontainer. Focus ();

 

// The item was found

Return true;

}

}

 

// If we get to this point, the selected item was not found at the current level, so we must check the children

Foreach (Object item in parentcontainer. Items)

{

Treeviewitem currentcontainer = parentcontainer. itemcontainergenerator. containerfromitem (item) as treeviewitem;

 

// If children exist

If (currentcontainer! = NULL & currentcontainer. Items. Count> 0)

{

// Keep track of if the treeviewitem was expanded or not

Bool wasexpanded = currentcontainer. isexpanded;

 

// Expand the current treeviewitem so we can check its child treeviewitems

Currentcontainer. isexpanded = true;

 

// If the treeviewitem child containers have not been generated, we must listen

// The statuschanged event until they are

If (currentcontainer. itemcontainergenerator. status! = Generatorstatus. containersgenerated)

{

// Store the event handler in a variable so we can remove it (in the handler itself)

Eventhandler Eh = NULL;

Eh = new eventhandler (delegate

{

If (currentcontainer. itemcontainergenerator. Status = generatorstatus. containersgenerated)

{

If (expandandselectitem (currentcontainer, itemtoselect) = false)

{

// The assumption is that code executing in this eventhandler is the result of the parent not

// Being expanded since the containers were not generated.

// Since the itemtoselect was not found in the children, collapse the parent since it was previusly collapsed

Currentcontainer. isexpanded = false;

}

 

// Remove the statuschanged event handler since we just handled it (we only needed it once)

Currentcontainer. itemcontainergenerator. statuschanged-= eh;

}

});

Currentcontainer. itemcontainergenerator. statuschanged + = eh;

}

Else // otherwise the containers have been generated, so look for item to select in the children

{

If (expandandselectitem (currentcontainer, itemtoselect) = false)

{

// Restore the current treeviewitem's expanded State

Currentcontainer. isexpanded = wasexpanded;

}

Else // otherwise the node was found and selected, so return true

{

Return true;

}

}

}

}

 

// No item was found

Return false;

}

}