c# - How to call functions in a main view model from other view models? -

my program composed of treeview , 2 contentpresenters @ ground level. mainwindow, treeview, , each contentpresenter have own viewmodels.

i call function in mainwindowviewmodel treeviewviewmodel.

i need because mainwindowviewmodel controls displayed in contentpresenters, , manually update display.

i'm guessing this...

treeviewviewmodel:

public class treeviewviewmodel {      //do need declare mainwindowvm?       public treeviewviewmodel() { ... }       private void function()      {           //command affects display            //manually call function in mainwindowvm refresh view      } } 

i have tried access mainwindowvm treeviewviewmodel using:

public mainwindowviewmodel viewmodel { { return datacontext mainwindowviewmodel; } } 

but doesn't make sense. because mwvm not datacontext of treeviewviewmodel.

the delegate method used in , linked answer can used in parent-child relationship , in either direction. includes child view model parent view model, window code behind code behind of child window, or pure data relationships without ui involved. can find out more using delegate objects delegates (c# programming guide) page on msdn.

i answered similar question earlier today. if take @ passing parameters between viewmodels post, you'll see answer involves using delegate objects. can replace these delegates (from answer) method(s) , work in same way.

please let me know if have questions.

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update >>>

yes, sorry forgot wanted call methods instead... i've been working on many posts tonight. still using example other post, call method in parameterviewmodel_onparameterchange handler:

public void parameterviewmodel_onparameterchange(string parameter) {     // call method here } 

think of delegate being path parent view model... it's raising event called readyforyoutocallmethodnow. in fact, don't need have input parameter. define delegate this:

public delegate void readyforupdate();  public readyforupdate onreadyforupdate { get; set; } 

then in parent view model (after attaching handler in other example):

public void childviewmodel_onreadyforupdate() {     // call method here     updatedisplay(); } 

as have multiple child view models, define delegate in class both have access to. let me know if have more questions.

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update 2 >>>

after reading last comment again, i've thought of simpler method might achieve want... @ least, if understand correctly. possible bind directly child views parent view model. instance, allow bind button.command property in child view icommand property in parent view model:

in treeviewview:

<button content="click me" command="{binding datacontext.parentcommand,  relativesource={relativesource ancestortype={x:type mainwindow}}}" /> 

this of course assumes instance of parent view model in question set datacontext of mainwindow.