WPF Binding textbox to property of static class not updating

Question

I have three textboxes meant to store numeric values, and three static classes with properties I would like to bind to the textboxes. I want the third textbox to equal the sum of the first two textboxes. I have a non-static class which has all of these properties (only showing Value for simplicity):

public class Field : PropertyValueChanged
{
    private string _value;

    public virtual string Value
    {
        get { return _value; }
        set
        {
            if (value != _value)
            {
                _value = value;
                NotifyPropertyChanged();
            }
        }
    }
}

Then I have the three static classes:

public static class FirstValueField
{
    public static Field FieldProperties;

    static FirstValueField()
    {
        FieldProperties = new Field();
    }
}

public static class SecondValueField
{
    public static Field FieldProperties;

    static SecondValueField()
    {
        FieldProperties = new Field();
    }
}

public static class TotalField
{
    public static Field FieldProperties = new Field();

    static TotalField()
    {
        FirstValueField.FieldProperties.PropertyChanged += TotalField_PropertyChanged;
        SecondValueField.FieldProperties.PropertyChanged += TotalField_PropertyChanged;
    }

    private static void TotalField_PropertyChanged(object sender, System.ComponentModel.PropertyChangedEventArgs e)
    {
        double val1, val2;
        if (FirstValueField.FieldProperties.Value == null)
        {
            val1 = 0;
        }
        else
        {
            val1 = Double.Parse(FirstValueField.FieldProperties.Value);
        }
        if (SecondValueField.FieldProperties.Value == null)
        {
            val2 = 0;
        }
        else
        {
            val2 = Double.Parse(SecondValueField.FieldProperties.Value);
        }
        FieldProperties.Value = (val1 + val2).ToString();
        MessageBox.Show("Changing TotalField to: " + FieldProperties.Value);
    }
}

My xaml looks like this:

    <TextBox x:Name="FirstValueField"
        Text="{Binding Source={x:Static local:FirstValueField.FieldProperties}, 
            Path=Value, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"/>

    <TextBox x:Name="SecondValueField"
        Text="{Binding Source={x:Static local:SecondValueField.FieldProperties}, 
            Path=Value, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"/>

    <TextBox x:Name="TotalField"
        Text="{Binding Source={x:Static local:TotalField.FieldProperties}, 
            Path=Value, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"/>

The problem is the TotalField.FieldProperties.Value is updating, but not the textbox text. I'm not sure what's wrong?

score 1 · Answer 1 · answered May 27 '17 at 17:02

You cannot bind to a field. You need to make it a property:

public static class FirstValueField
{
    public static Field FieldProperties{get; set;} //<-- See this needs to be property

    static FirstValueField()
    {
        FieldProperties = new Field();
    }
}

Do the same for your other classes.

WPF Binding textbox to property of static class not updating

1 Answers1