C# WPF TextBox 在文本更改时调用方法

Question

so I recently started coding a WPF MVVM program in C# for the first time and got into a bit of a problem. I made a filter TextBox where the user can type in something and it will filter a list according to it. so my XAML looks like this:

<TextBox Text="{Binding Path=SearchFilter, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"/>

So when a user inputs something it updates the SearchFilter and then I want it to run the LoadList() method. How would I do that without putting any extra call inside the setter of SearchFilter?

Answer 1

So I've completly missed something on my side, sorry for that. This approach should help you.

XAML

<TextBox Text="{Binding SearchFilter, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"
               TextChanged="TextBox_TextChanged"/>

Code Behind

private void TextBox_TextChanged(object sender, TextChangedEventArgs e)
{
  var viewmodel = DataContext as ViewModel1;

  viewmodel.LoadList();
}

In my case this is the ViewModel class, you should try using INotifyPropertyChanged as it will update your UI if you change something in the code and you will need it probably in the future anyways. Also this uses SetProperty which makes it just all cleaner and easier

public class ViewModel1 : INotifyPropertyChanged
{
  public string Title { get; } = "View 1";

  private string _searchFilter;
  public string SearchFilter 
  {
    get { return _searchFilter; }
    set 
    { 
      SetProperty(ref _searchFilter, value);
    }
  }

  public void LoadList()
  {
    Console.WriteLine("Value: "+SearchFilter);
    // your stuff you do in LoadList
  }

  public event PropertyChangedEventHandler PropertyChanged;
  protected virtual void OnPropertyChanged(string propertyName)
  {
    PropertyChangedEventHandler handler = PropertyChanged;
    if (handler != null) handler(this, new PropertyChangedEventArgs(propertyName));  
  }
  protected bool SetProperty<T>(ref T field, T value,
      [CallerMemberName] string propertyName = null)
  {
    if (EqualityComparer<T>.Default.Equals(field, value)) return false;
    field = value;
    OnPropertyChanged(propertyName);
    return false;
  }
}

Btw. sry for the past answer, I missed something that I always forget on this specific problem:/