对数据网格中的列进行自定义评估，并将Observable Collection绑定到DataGrid的列

Question

Situation : In general: I have a disc and want to measure the thickness. The measuring system are two sensors which have a defined distance from each other. The disc is than placed between these sensors which then measure their respective distance to the disc.

Precisely : The thickness is evaluated as an average over several values. So I measure the thickness at a specific radius and than rotate the disc and take the average over the whole rotation as mean value for that specific radius. Then the total average is taken over 5 such radius measurements.

Requirements : There should be a table which looks like this:

| radius | mean thickness | deviation|
--------------------------------------
|  5cm   |    700µm       |    10µm  |
|  7cm   |    702µm       |    11µm  |
|  9cm   |    695µm       |    17µm  |
| 11cm   |    699µm       |     9µm  |
| 12cm   |    703µm       |    12µm  |
--------------------------------------
mean:         700µm            10µm

General Question : How can I achieve that?

What I have done : I created a Class namend Disc which looks like this:

public class Disc
{
    private ObservableCollection<double> measuredRadii;
    public ObservableCollection<double> MeasuredRadii { get { return measuredRadii; } }

    private ObservableCollection<DistanceMeasurementsResults> measurementValues;
    public ObservableCollection<DistanceMeasurementsResults> MeasurementValues { get { return measurementValues; } }

    public Disc()
    {
        // these radii are read from settings file
        measuredRadii = new ObservableCollection<double>() { 5, 7, 9, 11, 12 };
        measurementValues = new ObservableCollection<DistanceMeasurementsResults>();
    }

    public void AddMeasurementsResults(DistanceMeasurementsResults results)
    {
        measurementValues.Add(results);
    }
}

And as you can see, there is a DistanceMeasurementsResults class:

public class DistanceMeasurementsResults
{
    public Point Position;
    public double DistanceFromSensor1;
    public double DistanceFromSensor2;
}

The Position has as X the radius and as Y the angle phi.

To realize the table I tried to use a DataGrid in my MainWindow.xaml. I thought I would fill the radii which are in disc.MeasuredRadii in to the first column, and then calculate the average thickness for each row with a neat little function like the following: let's assume I have the current row index as rowIndex . Then the average thickness for that row in column "mean thickness" would be calculated like:

var measurementValuesWithCurrentRadius = disc.MeasurementValues.Where(x => x.Position.X == disc.MeasuredRadii[rowIndex]);
var measuredThicknesses = measurementValuesWithCurrentRadius.Select(x => (DISTANCE_BETWEEN_SENSORS - x.DistanceFromSensor1 - x.DistanceFromSensor2));
double measuredThicknesses = measuredDistances.Average();

I hoped I could eventually bind this method to the second column (that with Header "mean thickness").

The relevant MainWindow.xaml looks like this:

<DataGrid x:Name="MeasureDataGrid" IsReadOnly="True" AutoGenerateColumns="False">
</DataGrid>

And then I tried to fill the DataGrid in the code-behind (MainWindow.xaml.cs). At first I just wanted to see the radii in the DataGrid, but I failed already at this point...

public partial class MainWindow : Window
{
    private Disc disc;

    public MainWindow()
    {
        disc = new Disc();

        DataGridTextColumn radiusColumn = new DataGridTextColumn();
        radiusColumn.Header = "radius";
        radiusColumn.Binding = new Binding("MeasuredRadii") { Source = this.disc };
        MeasureDataGrid.Columns.Add(radiusColumn);
    }
}

When I do this, then I get a blank DataGrid...

Specific Questions :

1. How can I bind the disc.MeasuredRadii to the first column of the DataGrid?
2. How can I calculate the other columns with the given Function?

Important : I don't want to add more Members to the Disc class. Because it already holds all the relevant data. And I want to do more statics in the table and I don't want to create a field for all these static data, because: What to do if I don't want to show all these statics? Then I would have to change the model in cause of a change in the view. This is against my personal rules...

Edit : I come from Winforms, and I thought I could use something like the CellFormating event to bind my neat little method to the DataGrid. Is there something similar in DataGrids?

Answer 1

First, your binding is not working because you are binding to a collection of doubles, therefore you have no property name. Also you have not set the ItemsSource for your DataGrid. This code fixes that issue.

        DataGridTextColumn radiusColumn = new DataGridTextColumn();
        radiusColumn.Header = "radius";
        radiusColumn.Binding = new Binding("");
        MeasureDataGrid.Columns.Add(radiusColumn);

        MeasureDataGrid.ItemsSource = disc.MeasuredRadii;

However, I believe want you really should do is to create a collection of a class that holds the properties you want to display. That doesn't necessarily mean new members, just properties using your neat functions to calculate the things you need.

Here's sort of what I'd suggest (a collection of this class would then replace your MeasuredRadii and MeasurementValues in your Disc class). Just a suggestion...

public class Measurement
{
    private double measuredRadius = 0.0;
    public double MeasuredRadius { get { return measuredRadius; } set { measuredRadius = value; } }
    public double MeasuredThickness
    {
        get
        {
            var measurementValuesWithCurrentRadius = MeasurementValues.Where(x => x.Position.X == MeasuredRadius);
            var measuredDistances = measurementValuesWithCurrentRadius.Select(x => (DISTANCE_BETWEEN_SENSORS - x.DistanceFromSensor1 - x.DistanceFromSensor2));
            return measuredDistances.Average();
        }
    }

    private ObservableCollection<DistanceMeasurementsResults> measurementValues;
    public ObservableCollection<DistanceMeasurementsResults> MeasurementValues { get { return measurementValues; } }

}