how to update textbox

Question

I'm new to WPF and am trying to update a textbox after a property has changed.

The textbox is bound in the MainWindow after the InitializeComponents is ran here

            Binding URLBinding = new Binding("FilePath");
            URLBinding.UpdateSourceTrigger = UpdateSourceTrigger.PropertyChanged;
            txtURL.SetBinding(ContentProperty, URLBinding);

and a button activates a FileDialogue to allow the textbox to gain a value here

    private void btnFilePath_Click(object sender, RoutedEventArgs e)
        {
            OpenFileDialog dlg = new OpenFileDialog();
            dlg.DefaultExt = ".xml";
            dlg.Filter = "Comprehensive Report (.xml)|*.xml";
            if (dlg.ShowDialog() == true)
            {
                tempJobItem.FilePath = dlg.FileName;
            }
        }

but this doesn't cause the txtURL to list the new value for the FilePath property.  What am I doing wrong?

Answer 1

Could you present some more of the code, where and how are you binding ?

As it seems from your snippet, you are doing this in codebehind, if that is the cause, there is no reason for the binding since you can just set the property of the textbox directly.

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Developing is part of being a developer.

Answer 2

The class containing FilePath must implement INotifyPropertyChanged event and when value get set in FilePath property, PropertyChanged event should be raised. 

Try following code

public class JobItem : System.ComponentModel.INotifyPropertyChanged
    {
        private string filePath;
 
        public string FilePath 
        { 
            get
            {
                return filePath;
            }
            set
            {
                filePath = value;
                OnPropertyChanged("FilePath");
            }
        }
 
        private void OnPropertyChanged(string propertyName)
        {
            if (PropertyChanged != null)
            {
                PropertyChanged(this, new System.ComponentModel.PropertyChangedEventArgs(propertyName));
            }
        }
        public event System.ComponentModel.PropertyChangedEventHandler PropertyChanged;
    }

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Gaurav Khanna | Microsoft VB.NET MVP

Answer 3

  public class SiteData : System.ComponentModel.INotifyPropertyChanged
    {
                private Uri filepath;
        public SiteData()
        {
        }
        public string FilePath
        {
            get 
            {
                if (filepath != null)
                    return filepath.LocalPath;
                else
                    return "";
            }
            set 
            {
                filepath = new Uri(value);
                OnPropertyChanged("FilePath");
            }
        }
        private void OnPropertyChanged(string propertyName)
        {
            if (PropertyChanged != null)
            {
                PropertyChanged(this, new System.ComponentModel.PropertyChangedEventArgs(propertyName));
            }
        }
        public event System.ComponentModel.PropertyChangedEventHandler PropertyChanged;
    }

I did what you said, but it still doesn't work.

Answer 4

I found the problem.

When I wrote

Binding URLBinding = new Binding("FilePath");
URLBinding.UpdateSourceTrigger = UpdateSourceTrigger.PropertyChanged;
txtURL.SetBinding(ContentProperty, URLBinding);

I should have wrote

Binding URLBinding = new Binding("FilePath");            
txtURL.SetBinding(TextBox.TextProperty, URLBinding);

Answer 5

Good to hear !

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Developing is part of being a developer.