c# - Asynchronous function call inside tree loader extension function -

c# - Asynchronous function call inside tree loader extension function -

i have function load children of node. internally calls wcf async service load. signature follows.

public void addchildelements(node parentelement, action<ienumerable<node>> callback) { }

this can used like

_nodebuilder.addchildelements(parentelement, (elements) => { //do elements });

now want write function expand hierarchy based on condition. write extension function this

public static t loadhierarchyuntilitemfound<t>( ienumerable<t> sequence, func<t, list<t>> loadaction, func<t, string> searchstring) { //... }

the loadaction parameter expects loading function node.the usage follows

elements.loadhierarchyuntilitemfound(loadchildren, "root.uk.england.london");

the problem how write loading function?

private list<node> loadchildren(node parent) { // _nodebuilder.addchildelements(parent, here expects callback //which gives result, how utilize this?); }

in short, problem how can utilize callback function homecoming result wrapper function?

if want is possible create function calls async method , blocks until returns:

private list<node> loadchildren(node parent) { var tcs = new taskcompletionsource<ienumerable<node>>(); addchildelements(parent, nodes => tcs.setresult(nodes)); homecoming tcs.task.result.tolist(); }

however, in many contexts preferable entire thing asynchronously, rather synchronously.

public static async task<t> loadhierarchyuntilitemfoundasync<t>( ienumerable<t> sequence, func<t, task<ienumerable<t>>> loadaction, func<t, string> selector, string searchstring) { var stack = new stack<t>(sequence); while (stack.any()) { var item = stack.pop(); if (selector(item) == searchstring) homecoming item; foreach (var kid in await loadaction(item)) { stack.push(child); } } homecoming default(t); }

given function can phone call using:

elements.loadhierarchyuntilitemfound(addchildelements, "root.uk.england.london");

c# asynchronous callback hierarchical-data