Question

I have a user control as under where I have exposed a public property. Based on the property value set, I am trying to creat the labels at runtime

public partial class MyUserControl : UserControl
    {
        public int SetColumns { get; set; }

        public MyUserControl()
        {
            InitializeComponent();

            myGrid.Children.Clear();
            myGrid.RowDefinitions.Add(new RowDefinition());

            for (int i = 0; i < SetColumns; i++)
            {
                //Add column.         
                myGrid.ColumnDefinitions.Add(new ColumnDefinition());
            }

            for (int j = 0; j < SetColumns; j++)     
            {                           
                Label newLabel = new Label();
                newLabel.Content = "Label" + j.ToString();
                newLabel.FontWeight = FontWeights.Bold;
                newLabel.HorizontalAlignment = System.Windows.HorizontalAlignment.Right;
                Grid.SetRow(newLabel, 0);
                Grid.SetColumn(newLabel, j);
                myGrid.Children.Add(newLabel);
            }
        }
    }

This user control is being invoked from a window as under

<Window x:Class="WpfApplication2.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:local ="clr-namespace:WpfApplication2"
        Title="MainWindow" Width="300" Height="300">
    <Grid >
        <local:MyUserControl SetColumns="10"></local:MyUserControl>
    </Grid>
</Window>

The problem is that, the value is always coming as zero(0) in the user control property and hence nothing is getting created.

What mistake I am making? Please help.

Answer 1

SetColumns is a property, you’re reading it’s value in constructor, but all properties are set AFTER constructor call. So externally XAML parser does something like this:

var userControl = new MyUserControl(); // here you're trying to read `SetColumns`
userControl.SetColumns = 10; // here they are actually set

Try updating your control in SetColumns property setter:

private int _setColumns;
public int SetColumns 
{
    get { return { _setColumns; } }
    set
    {
        _setColumns = value;
        UpdateControl();
    }
}