Question

How to provide the outer glow effect to border?

<Grid Width="200" Height="200">
    <Grid.Background>
        <RadialGradientBrush Center="0.5,0.5" GradientOrigin="0.5,0.5" RadiusX="0.8" RadiusY="0.8">
            <RadialGradientBrush.GradientStops>
                <GradientStop Offset="0" Color="#FF123B5F" />
                <GradientStop Offset="1" Color="#FF001F31" />
            </RadialGradientBrush.GradientStops>
        </RadialGradientBrush>
    </Grid.Background>
    <Border Width="180" Height="180" Margin="10" Background="Transparent"
            BorderBrush="White" BorderThickness="1">
        <Border.BitmapEffect>
            <OuterGlowBitmapEffect GlowColor="White" GlowSize="3" Opacity="1" />
        </Border.BitmapEffect>
    </Border>
</Grid>

I have tried this but it not working

Answer 1

BitmapEffects are no longer supported in .NET 4.0.

From MSDN

Important In the .NET Framework 4 or later, the BitmapEffect class is
obsolete. If you try to use the BitmapEffect class, you will get an
obsolete exception. The non-obsolete alternative to the BitmapEffect
class is the Effect class. In most situations, the Effect class is
significantly faster.

It isn’t the same thing but you can try with a DropShadowEffect with ShadowDepth close to 0 instead.

Example

<Border Width="180" Height="180" Margin="10" Background="Transparent"
        BorderBrush="White" BorderThickness="2" Opacity="1.0">
    <Border.Effect>
        <DropShadowEffect ShadowDepth="0"
                          Color="White"
                          Opacity="1"
                          BlurRadius="5"/>
    </Border.Effect>
</Border>

Comparison between the BitmapEffects you had and DropShadowEffect above. DropShadowEffect to the right.