在xaml中获取数据网格内部的scrollviewer的宽度

Question

I am building a UI in xaml (WPF), and I have a datagrid with autogenerated columns which fills its container (a dockpanel ), but also has frozen columns.

Depending on the size of the window and the amount of data in the grid, the none frozen columns on the right automatically get an horizontal scrollbar.

I am interested in retrieving the width of the scrollviewer from inside the datagrid that it is visible when the datagrid becomes bigger than the dockpanel , possibly in xaml directly to bind it to another element, or in the code behind if the first option is not possible. I would also like to retrieve the width of the content inside the scrollviewer .

I thought of getting the actual width of the surrounding elements and do a bit of calculation but that sounds tedious...

Does anybody have a suggestion?

Thanks

Answer 1

With the help of this post "access-scrollview-properties-of-a-datagrid-in-wpf" I managed to access the scrollviewer of the datagrid via the visual tree.

However, despite checking several properties of the scrollviewer , I wasn't able to find what I am looking for.

So, I eventually calculated the size myself (width of the datagrid - width of the frozen columns). I think that I will also calculate the width of the other columns to get the width of the content inside the scrollviewer ...

Here is a simple example to run in Blend (proj name: GridScrollViewer ):

MainWindow.xaml:

<Window x:Class="GridScrollViewer.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    xmlns:local="clr-namespace:GridScrollViewer"
    mc:Ignorable="d"
    Title="MainWindow" Height="350" Width="525">
<DockPanel
    LastChildFill="True"
    Margin="10">

    <StackPanel
        Width="auto"
        Orientation="Horizontal"
        DockPanel.Dock="Bottom">
        <TextBlock Text="Scrollviewer offset: "/>
        <TextBlock Name="myScrollViewerOffsetText"  Text=""/>
    </StackPanel>

    <StackPanel
        Width="auto"
        Orientation="Horizontal"
        DockPanel.Dock="Bottom">
        <TextBlock Text="Scrollviewer width?: "/>
        <TextBlock Name="myScrollViewerText"  Text=""/>
    </StackPanel>

    <StackPanel
        Width="auto"
        Orientation="Horizontal"
        DockPanel.Dock="Bottom">
        <TextBlock Text="Expected value for scrollviewer width: "/>
        <TextBlock Name="myExpectedValueText"  Text=""/>
    </StackPanel>

    <StackPanel
        Width="auto"
        Orientation="Horizontal"
        DockPanel.Dock="Bottom">
        <TextBlock Text="First four columns width: "/>
        <TextBlock Name="myColumnsText" Text=""/>
    </StackPanel>

    <StackPanel
        Width="auto"
        Orientation="Horizontal"
        DockPanel.Dock="Bottom">
        <TextBlock Text="Datagrid width: "/>
        <TextBlock Text="{Binding ElementName=myGrid, Path=ActualWidth}"/>
    </StackPanel>

    <DataGrid
        ItemsSource="{Binding}"
        Name="myGrid"
        DockPanel.Dock="Top"
        Margin="0,0,0,10"
        FrozenColumnCount="4"
        HorizontalScrollBarVisibility="Visible"
        HeadersVisibility="Column"
        CanUserAddRows="False"
        CanUserDeleteRows="False"
        CanUserResizeColumns="True"
        LayoutUpdated="myGrid_LayoutUpdated"
        />

</DockPanel>

MainWindow.xaml.cs:

using System;
using System.Data;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Media;

namespace GridScrollViewer
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
            CreateDataGrid();
        }

        public void CreateDataGrid()
        {
            DataTable dt = new DataTable();

            dt.Columns.Add("Col 1", typeof(string));
            dt.Columns.Add("Col 2", typeof(string));
            dt.Columns.Add("Col 3", typeof(string));
            dt.Columns.Add("Col 4", typeof(string));
            dt.Columns.Add("Col 5", typeof(int));
            dt.Columns.Add("Col 6", typeof(int));
            dt.Columns.Add("Col 7", typeof(int));
            dt.Columns.Add("Col 8", typeof(int));
            dt.Columns.Add("Col 9", typeof(int));
            dt.Columns.Add("Col 10", typeof(int));
            dt.Columns.Add("Col 11", typeof(int));
            dt.Columns.Add("Col 12", typeof(int));
            dt.Columns.Add("Col 13", typeof(int));
            dt.Columns.Add("Col 14", typeof(int));

            for (int i = 0; i < 10; i++)
            {
                dt.Rows.Add("First field",
                    "Second field",
                    "Third field",
                    "Fourth field",
                    100*i+i,
                    100 * i + i+1,
                    100 * i + i+2,
                    100 * i + i+3,
                    100 * i + i+4,
                    100 * i + i+5,
                    100 * i + i+6,
                    100 * i + i+7,
                    100 * i + i+8,
                    100 * i + i+9);
            }

            myGrid.DataContext = dt;
        }

        public void UpdatemyColumnsText()
        {
            double size = 0;
            if (myGrid.Columns.Count > 4)
            {
                size = myGrid.Columns[0].ActualWidth
                + myGrid.Columns[1].ActualWidth
                + myGrid.Columns[2].ActualWidth
                + myGrid.Columns[3].ActualWidth;
            }
            myColumnsText.Text = ((int)size).ToString();
        }

        public void UpdateScrollViewerText()
        {
            ScrollViewer sc = (ScrollViewer)VisualTreeHelper.GetChild(
                (VisualTreeHelper.GetChild(myGrid, 0)), 0);
            myScrollViewerText.Text = "actual width: " + (int)sc.ActualWidth
                +" - desired size: " + (int)sc.DesiredSize.Width
                +" - render size: " + (int)sc.RenderSize.Width
                +" - viewport: " + (int)sc.ViewportWidth;

            myScrollViewerOffsetText.Text = ((int)sc.HorizontalOffset).ToString();
        }

        public void UpdateExpectedWidth()
        {
            double expectedWidth = 0;
            if (myGrid.Columns.Count > 4)
            {
                expectedWidth = myGrid.ActualWidth -(myGrid.Columns[0].ActualWidth
                + myGrid.Columns[1].ActualWidth
                + myGrid.Columns[2].ActualWidth
                + myGrid.Columns[3].ActualWidth);
            }
            myExpectedValueText.Text = ((int)expectedWidth).ToString();
        }

        private void myGrid_LayoutUpdated(object sender, EventArgs e)
        {
            UpdatemyColumnsText();
            UpdateScrollViewerText();
            UpdateExpectedWidth();
        }

    }
}

This mostly answer my question, but if anybody has a better alternative, I'd be very happy to read about it.