c# - Duplicate Model instantiated from InitializeComponent() -


i'm working on mvvm wpf application , have run dead end trying solve this. %)

have model class devicemodel instantiated app.xaml.cs. model implements inotifypropertychanged interface.

public partial class app : application {     public devicemodel devicemodelinstance { get; set; }      public app()     {         devicemodelinstance = new devicemodel();     } }


in app.xaml:

<application.resources>     <vm:viewmodelbase x:key="viewmodelbaseapp"/>     <m:devicemodel x:key="devicemodelapp"/> </application.resources>

then mainwindow.xaml instantiate viewmodelbase:

    <window.datacontext>          <binding source="{staticresource viewmodelbaseapp}"/>     </window.datacontext>

then bind buttons in ui (mainwindow.xaml) commands in viewmodelbase, implement icommand interface:

    command="{binding inputphantomcommand, converter={staticresource inputphantomconverter}, source={staticresource viewmodelbaseapp}}"

this works great! push button, command in viewmodelbase gets called , changes property of devicemodelinstance (instantiated in app.xaml.cs), in turn triggers propertychanged event, propagates other classes listening event. icommand bound buttons in ui work way.

however, when bind sliders properties in devicemodel class, i.e.:

    value="{binding inputchannel2.gain, converter={staticresource inputgainconverter}, source={staticresource devicemodelapp}}"

all of sliders bound duplicate devicemodel class, gets instantiated @ initializecomponent() method in constructor of mainwindow.xaml.cs. when move of sliders, duplicate model reacts fine changes. of labels bound same properties sliders dynamically updated. yet, of events listened on original devicemodelinstance object (from app.xaml.cs) , no events occur, obviously.

i cannot figure out why of buttons interacting devicemodelinstance created in app.xaml.cs, while of sliders , corresponding labels interacting duplicate devicemodel() gets created @ initializecomponent() of mainwindow...

i suspect it's issue of referencing original devicemodelinstance correctly in xaml, don't know how this. thank you! )

so, in addition clues given in comments , clemens, somehow answer cleared me more - multiple instances of viewmodel

specifically, line:

to access in code-behind, grab adminviewmodel (adminviewmodel)this.datacontext.

in case, after relocating devicemodelinstance app class viewmodelbase class, setting public property, instantiating viewmodelbase instance via xaml:

    <window.datacontext>          <vm:viewmodelbase/>     </window.datacontext>

and referencing specific viewmodelbase instance:

public partial class mainwindow : window {     public viewmodelbase vm;      public mainwindow()     {         vm = (viewmodelbase)this.datacontext;         initializecomponent();     }

this works me intended because 1 instance of viewmodelbase (and subsequently 1 instance of devicemodel) gets instantiated via xaml , gets referenced in code-behind. however, still don't understand how same other way around, i.e. instantiating model objects in code , referencing them in xaml, not creating new instances.

thanks!


Comments

Post a Comment

Popular posts from this blog

android - InAppBilling registering BroadcastReceiver in AndroidManifest -

i'm implementing inapp billing in android app. works well, however, i'm trying decouple broadcast receiver activity manifest. suggestion in android's trivialdrive sample: // important: dynamically register broadcast messages updated purchases. // register receiver here instead of <receiver> in manifest // because call getpurchases() @ startup, therefore can ignore // broadcasts sent while app isn't running. // note: registering listener in activity bad idea, done here // because sample. regardless, receiver must registered after // iabhelper setup, before first call getpurchases(). currently there's class extends broadcastreceiver : public class iabbroadcastreceiver extends broadcastreceiver { /** * intent action receiver should filter for. */ public static final string action = "com.android.vending.billing.purchases_updated"; private final iabbroadcastlistener mlistener; public iabbroadcastreceiver(iabbroadcastlistener listener) { m...
Read more

python Tkinter Capturing keyboard events save as one single string -

is possible store keyboard events 1 string? code below stores 1 char , prints it. card reader or bar code reader, contains collection of character/ string not 1 character @ time. goal save char pressed text variable. from tkinter import * root = tk() def key(event): text= event.char text+= event.char print ("pressed", text) def callback(event): frame.focus_set() print ("clicked at", event.x, event.y) frame = frame(root, width=100, height=100) frame.bind("<key>", key) frame.bind("<button-1>", callback) frame.pack() root.mainloop() currently, creating text variable , everytime key() function gets called, , text stores last character typed. you can define text module level variable , , use module level text inside key function - text = '' def key(event): global text text+= event.char print("pressed", text)
Read more

sql server - Why does Linq-to-SQL add unnecessary COUNT()? -

here tables: create table customer ( cid int primary key, name varchar(32) ) create table ord ( oid int primary key, cid int foreign key references customer, address varchar(20) ) here's linq-to-sql statement: var aaa = c in db.customer select new { c, o = c.ord.tolist() }; and here's inexplicable query generated linq-to-sql: select [t0].[cid] [cid], [t0].[name] [name], [t1].[oid] [oid], [t1].[cid] [cid2], [t1].[address] [address], (select count(*) [dbo].[ord] [t2] [t2].[cid] = [t0].[cid]) [value] [dbo].[customer] [t0] left outer join [dbo].[ord] [t1] on [t1].[cid] = [t0].[cid] order [t0].[cid], [t1].[oid] i want understand how rid of count(*) part. it's entirely uncalled for! linq needs count(*) in order determine number of entries returned o = c.ord.tolist() .
Read more