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PODatabinding updating with outdated values
 

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    <p>I am not understanding the following 4 points about databinding. Not sure if i get unexpected results (outdated data in code behind), or if this is just a result of me misunderstanding how things work.</p> <ol> <li>Bound data to a textbox updates when i leave the textbox. What event EXACTLY does this? LostFocus? </li> <li>When using the now changed data in code behind it seems to still use the OLD data. Why is this happening? Could point 3 be the reason?</li> <li>After the textbox updates i did a test and set datacontext to nothing and reaplied datacontext to the same scource. The values shown are the values before i edited them. Why did they show up after editing, but returned to the old values after rebinding?</li> <li>After changing the values for the second time it seems like code behind uses the data after my first change. Rebinding like in point 3 leads to the same result (value after first change, second change ignored). Seems like code behind is always one update behind, can i change this?</li> </ol> <p>Anyone able to explain why this happens? </p> <p><strong>Desired behavior:</strong></p> <p>I want the people count to update when I edit the housing count. Preferable on the fly, but after losing focus is fine. When losing focus the value for isle ID 0 should be the right one tho, and not the outdated value.</p> <p><strong>For easier understanding</strong>, a picture with 3 screens and related code samples. </p> <p><a href="http://www.mathematik-lehramtsstudium.de/BindingExample.jpg" rel="nofollow">http://www.mathematik-lehramtsstudium.de/BindingExample.jpg</a></p> <p><strong>My class:</strong></p> <pre><code>//class for isles public class isle : INotifyPropertyChanged { //Dummyvariables,... private int _intBauer; private int _intBauerBev; //variables public int intIsleID { set; get; } //isle ID public string strName { set; get; } //isle name public int intBauer //housing count { set { this._intBauer = value; NotifyPropertyChanged("intBauer"); NotifyPropertyChanged("intBauerBev"); } get { return _intBauer; } } public int intBauerBev //each house hosts 8 people { set { this._intBauerBev = value;} get { return intBauer * 8; } } protected void NotifyPropertyChanged(String propertyName) { if (PropertyChanged != null) { PropertyChanged(this, new PropertyChangedEventArgs(propertyName)); } } public event PropertyChangedEventHandler PropertyChanged; } </code></pre> <p><strong>LostFocus-Event for updating the right side oft he page</strong></p> <pre><code> private void textboxHäuser_LostFocus(object sender, RoutedEventArgs e) { //Gesamtzahl neu berechnen listIsles[0].intBauer = 0; for (int i = 1; i &lt; 10; i++) { listIsles[0].intBauer += listIsles[i].intBauer; } //hard refresh DataContext, since it does not seem to update itself //leaving these two lines out of my code changes nothing tho, as expected gridInfoGesamt.DataContext = ""; gridInfoGesamt.DataContext = listIsles[0]; } </code></pre>
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    1. USMarco Heumann
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    1. COYou can read all about the answer to question 1 [here](http://msdn.microsoft.com/en-us/library/ms754356%28v=vs.110%29.aspx). If your UI isn't updating your view model then there is something wrong with the bindings. Post your XAML. If your UI *is* updating your view model then it's obviously much easier to react to it in your properties' setters or, failing that for some reason, by handling your view model's PropertyChanged event.
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    2. COThanks for your comment. I seem to have found the right pages and fixed my own issue while you where typing. Your link to Question 1 does explain this in more detail tho and i will read trough it a few times to make sure i don't fall for this trap again in the future. Thanks again!
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