Xamarin Searchbar with MVVM-CodePudding

There are quite a few articles about how to use the Xamarin SearchBar with MVVM pattern. The problem is that all these articles bind the PerformSearch event to an MVVM command.

I think these days, most users expect to see some results as they type and not once they tap "Search". So, I tried using the Xamarin Community Toolkit's EventToCommandBehavior to bind the TextChanged event to my MVVM command. It looks like this:

<SearchBar
   x:Name="CompanySearch"
   Placeholder="Search companies..."
   PlaceholderColor="#777777"
   BackgroundColor="{StaticResource PrimaryBackground}"
   TextColor="{StaticResource SecondaryDark}">
   <SearchBar.Behaviors>
      <xct:EventToCommandBehavior
         EventName="TextChanged"
         Command="{Binding SearchTextChanged}"
         CommandParameter="{Binding Text, Source={x:Reference CompanySearch}}"/>
   </SearchBar.Behaviors>
</SearchBar>

This works nicely UNTIL the user taps "Cancel" on iOS. Then it crashes the app with the following error:

Invalid type for parameter. Expected Type System.String, but received Type Xamarin.Forms.TextChangedEventArgs

That's because the method that handles the search in my model view is expecting string which looks like this:

async Task On_Search_Text_Changed(string keyword)
{
   if(!string.IsNullOrEmpty(keyword) && keyword.Length > 3)
   {
      var data = await _myApi.CompanySearch(keyword);
      if (data != null && data.Count > 0)
         Suggestions = new ObservableRangeCollection<CompanyModel>(data);
   }
}

Any idea how to handle the cancel event with EventToCommandBehavior? I'm also open to another approach for as long as I can perform the search on TextChanged and NOT on PerformSearch.

CodePudding user response：

just wrap it in a try/catch to trap the exception, or try this

async Task On_Search_Text_Changed(object keyword)
{
   if (keyword is string) 
   {
     ...
   }
}