UWP C# Scroll to the bottom of TextBox

Question

How do you scroll to the bottom of a TextBox for a UWP app?

With my transition to UWP, this has been one of the questions that hasn\'t been straight-forward.

Answer 1

If anyone needs to scroll to the bottom of a TextBox in UWP apps:

https://code.msdn.microsoft.com/windowsapps/How-to-scroll-to-the-a8ea5867

private void TextBox_TextChanged(object sender, TextChangedEventArgs e) 
{ 
    var grid = (Grid)VisualTreeHelper.GetChild(textBox1, 0); 
    for (var i = 0; i <= VisualTreeHelper.GetChildrenCount(grid) - 1; i++) 
        { 
            object obj = VisualTreeHelper.GetChild(grid, i); 
            if (!(obj is ScrollViewer)) continue; 
            ((ScrollViewer)obj).ChangeView(0.0f, ((ScrollViewer)obj).ExtentHeight, 1.0f); 
            break; 
        } 
    }
}

where textBox1 is the TextBox you want to scroll to the bottom.

Answer 2

Using the answer from https://code.msdn.microsoft.com/windowsapps/How-to-scroll-to-the-a8ea5867 sometimes caused lines to be deleted when scrolling up.

To fix that, try this:

private void ScrollToBottom(TextBox textBox)
{
    var grid = (Grid)VisualTreeHelper.GetChild(textBox, 0);
    for (var i = 0; i <= VisualTreeHelper.GetChildrenCount(grid) - 1; i++)
    {
        object obj = VisualTreeHelper.GetChild(grid, i);
        if (!(obj is ScrollViewer)) continue;
        ((ScrollViewer)obj).ChangeView(0.0f, ((ScrollViewer)obj).ExtentHeight, 1.0f, true);
        break;
    }
}

The main difference is this line:

((ScrollViewer)obj).ChangeView(0.0f, ((ScrollViewer)obj).ExtentHeight, 1.0f, true);

I also separated the method from the event handler, because I didn't want to necessarily scroll every time the text was changed.

Answer 3

An equivalent to the previous answer in C++/CX:

using Windows::UI::Xaml::Media::VisualTreeHelper;
using Windows::UI::Xaml::Controls::Grid;
using Windows::UI::Xaml::Controls::ScrollViewer;
using Platform::Object;

void
MainPage::responseTextUpdated(Platform::Object^ sender, Windows::UI::Xaml::RoutedEventArgs^ e)
{
    Grid^ grid = static_cast<Grid^>(VisualTreeHelper::GetChild(responseText, 0));
    for (int i = 0; i < VisualTreeHelper::GetChildrenCount(grid); ++i)
    {
        Object^ child = VisualTreeHelper::GetChild(grid, i);
        ScrollViewer^ scrollViewer = dynamic_cast<ScrollViewer^>(child);
        if (scrollViewer == nullptr) continue;

        double const horizontalOffset = 0;
        double const verticalOffset = scrollViewer->ExtentHeight;
        float const zoomFactor = 1;

        scrollViewer->ChangeView(horizontalOffset, verticalOffset, zoomFactor);
        break;
    }
}

Where responseText is TextBox^ responseText, the TextBox you want to scroll (probably the same as sender).