WPF: How do you modify the contents of a UIElement?

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Hello.

Is there a way to modify a UIElement's contents?
I have something like this:

System.IO.FileStream rdr = System.IO.File.OpenRead(xamlFilePath);
System.Windows.UIElement uie = (System.Windows.UIElement)System.Windows.Markup.XamlReader.Load(rdr);

And when I run the debugger and add uie to the "Watch" window, it gives me the following:

[-]uie
[-]System.Windows.Controls.Textbox          {System.Windows.Controls.Textbox:Title}
<some stuff...>
Text                                        "Title"

Now I need to be able to do two things: (1) read the Text in the textbox, and (2) modify it whenever I want.
I was hoping for something in the lines of:

{
Textbox tb = (Textbox)uie.GetChild();
tb.Text = "New Title"
uie.SetChild(tb);
}

, but it does not work like that. If anyone can point me to the method that performs this function I'd really appreciate it.

Thanks.

Posted 25-Oct-10 10:43am

Software_Guy

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Nish Nishant · Answer 1 · 2010-10-25T14:46:00

Solution 1

Here's some sample code:

C#

private void Window_Loaded(object sender, RoutedEventArgs e)
{
    string xaml = @"<StackPanel xmlns=""http://schemas.microsoft.com/winfx/2006/xaml/presentation""><TextBox Width=""150"" Height=""25"" /></StackPanel>";
    var ui = System.Windows.Markup.XamlReader.Parse(xaml) as FrameworkElement;
    var textBox = VisualTreeHelper.GetChild(ui, 0) as TextBox;
    textBox.Text = DateTime.Now.ToLongTimeString();

    mainGrid.Children.Add(ui);
}

mainGrid is a Grid control. The dynamically loaded content is added to this Grid.

Posted 25-Oct-10 14:46pm

Nish Nishant

Updated 25-Oct-10 14:47pm

v2

Comments

Software_Guy 25-Oct-10 21:06pm

Thank you for your reply. Unfortunately, I'm using C# and don't know much about VB. Could you help me with the translation of just the next line?

var textBox = VisualTreeHelper.GetChild(ui, 0) as TextBox;

The best I'm coming up with is:
System.Windows.Forms.TextBox tb = (System.Windows.Forms.TextBox)System.Windows.Media.VisualTreeHelper.GetChild(uie, 0);

, and it's not compiling (Error 8: Cannot convert type 'System.Windows.DependencyObject' to 'System.Windows.Forms.TextBox').

Nish Nishant 25-Oct-10 21:07pm

Uhm, what I posted is C# code. So you don't need to do any conversion.