How to set background opacity and border opacity in XAML?

I have a TextBox:

<TextBox x:Name="myTextBox"/>

The TextBox in code behind has two booleans:

 myTextBox.Background.Opacity = 0;
 myTextBox.BorderBrush.Opacity = 0;

Now this is all good and dandy, but how do I set these two properties in XAML?

Btw, setting:

<TextBox x:Name="myTextBox" Background="#00FFFFFF"/>

Does not effect the Opacity property. I'd like to specifically set t开发者_运维知识库hat opacity property in XAML.

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You want to do something like this:

<TextBlock Text="foo bar">
    <TextBlock.Background>
        <SolidColorBrush Color="Azure" Opacity="0.5" />
    </TextBlock.Background>
</TextBlock>

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Opacity in XAML is defined as a double, not an HTML color triplet.

http://msdn.microsoft.com/en-us/library/system.windows.uielement.opacity.aspx

You'll want to set it like this:

<TextBlock Opacity="0" />

You can also use a brush to set it:

<SolidColorBrush Color="#FF295564" Opacity="0.3"/>

...and then set the background property to your brush.

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I don't know when or if this was changed in the past, but at least with WPF 4.5 it's perfectly fine to use 8-digit-hex-color-codes:

<Element Background="#19ff0000"/> // background will be red with an alpha of 10%

The first two digits specify the alpha channel, with 00 (0) beeing fully transparent and FF (255) beeing fully opaque.

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If you just want a transparent background in XAML there is a Transparent preset:

<Border Background="Transparent"/>