CODEWITHSUNDEEP
c#wpfxamldependency-properties
imgnx
imgnx

Reputation: 789

SetValue for Dependency Property requires an object: How do I set the FontSizeProperty?

Another way of asking this would be to say:

"How do I set the value of an object to 24 so I can pass it as an argument to the SetValue()'s value parameter?"

To be clear: I'm just trying to set the value of a dependency property in the code behind

Here is my code:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

namespace Foo {

  public partial class MainWindow : Window {
    public MainWindow() {
      InitializeComponent();

      TextBlock1.Text = "bar";

      TextBlock1.SetValue(FontSizeProperty, 24);
    }
  }
}

When I build the app, it succeeds!

But when I debug, it throws an Argument Exception as shown here:

Argument Exception because my value is not an object

Why am I getting this error and/or how do I fix it?

Upvotes: 0

Views: 521

Answers (1)

Kevin Gosse
Kevin Gosse

Reputation: 39007

FontSize expects a double.

Just add ".0" at the end of your value to tell the compiler it's supposed to be a double:

TextBlock1.SetValue(FontSizeProperty, 24.0);

You can also use the "d" suffix:

TextBlock1.SetValue(FontSizeProperty, 24d);

As much as possible, you should use the strongly-typed property instead of the dependency property. This way, you can use implicit casting whenever possible, and the type errors will be caught at compilation time:

TextBlock1.FontSize = 24;

Behind the scenes the property will update the dependency property. So you get the exact same features, but with type-safety.

Upvotes: 5

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