OxyPlot - WPF PlotView does not update property

Question

I have a PlotView that has the height binds to the property ModelHeight in the view model.

MainWindow.xaml

<oxy:PlotView x:Name="IOPlot" Model="{Binding IOPlotModel}" Height="{Binding ModelHeight, UpdateSourceTrigger=PropertyChanged}" Width="630">

ViewModel.cs

private double modelheight = 300;
public double ModelHeight { 
        get{return modelheight;}
        set { modelheight = value;
        RaisePropertyChanged("ModelHeight");
        RaisePropertyChanged("IOPlotModel");
        this.IOPlotModel.InvalidatePlot(false); 
        }
    }

The problem is that: it doesn't update the height with the data binding! The height only changes once during the startup of the PlotModel. It seems like the height is fixed (IOPlotModel.Height always equals 300 even though ModelHeight changed). Does anyone know how to fix this issue?

Could be several things: Does the view model declare (not only implement) INotifyPropertyChanged? Is the DataContext set correctly in the view? Is the plot maybe inside a layout container that constraints it's height? In order to definitely answer your question, we would need to see more of the context around the code you have shared. However, I can already post a minimum working example (where view and view model are the same class) as an answer. Maybe it helps already. — Döharrrck, Mar 18 '22 at 16:56
@Đøharrrck I just found out that my view model didn't declare INotifyPropertyChanged! Thank you. — Trang Vo, Mar 22 '22 at 16:31

score 0 · Accepted Answer · answered Mar 18 '22 at 17:01

In this minimal example view and view model are the same class MainWindow, so the DataContext is set to this inside the constructor. Usually it should be the view model in a MVVM architecture.

XAML:

<Window x:Class="PlotTest.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:oxyplot="http://oxyplot.org/wpf"
    mc:Ignorable="d"
    Title="MainWindow" 
    Height="450" 
    Width="800">
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="30" />
            <RowDefinition Height="*" />
        </Grid.RowDefinitions>

        <TextBox x:Name="HeightTextBox"
                 Width="200"
                 TextChanged="HeightTextBox_TextChanged" />

        <oxyplot:PlotView Grid.Row="1"
                          Model="{Binding MyModel, UpdateSourceTrigger=PropertyChanged}"
                          Height="{Binding ModelHeight, UpdateSourceTrigger=PropertyChanged}" />
    </Grid>
</Window>

Code behind:

using OxyPlot;
using System.ComponentModel;
using System.Windows;

namespace PlotTest
{
    public partial class MainWindow : Window, INotifyPropertyChanged
    {
        private double modelheight = 300;

        public MainWindow()
        {
            this.DataContext = this;
            this.MyModel = new PlotModel() { Background = OxyColors.AliceBlue };

            InitializeComponent();
        }

        public event PropertyChangedEventHandler PropertyChanged;

        public double ModelHeight
        {
            get { return modelheight; }
            private set
            {
                modelheight = value;
                this.RaisePropertyChanged("ModelHeight");
            }
        }

        public PlotModel MyModel { get; private set; }

        private void HeightTextBox_TextChanged(object sender, System.Windows.Controls.TextChangedEventArgs e)
        {
            if (double.TryParse(this.HeightTextBox.Text, out double height))
            {
                this.ModelHeight = height;
            }
        }

        private void RaisePropertyChanged(string propertyName = "")
        {
            this.PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
        }
    }
}

OxyPlot - WPF PlotView does not update property

1 Answers1