I've done it this way:
<Style x:Key="Button" BasedOn="{StaticResource LoginButton}" TargetType="Button">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="Button">
<Grid>
<Border CornerRadius="4">
<Border.Background>
<LinearGradientBrush EndPoint="0,1">
<GradientStop Offset="0" Color="#0863a5" />
<GradientStop Offset="1" Color="#00457d" />
</LinearGradientBrush>
</Border.Background>
</Border>
<ContentPresenter HorizontalAlignment="Center" VerticalAlignment="Center"/>
</Grid>
</ControlTemplate>
</Setter.Value>
</Setter>
<Style.Triggers>
<Trigger Property="IsEnabled" Value="false">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="Button">
<Grid>
<Border CornerRadius="4">
<Border.Background>
<LinearGradientBrush EndPoint="0,1">
<GradientStop Offset="0" Color="#508fbd" />
<GradientStop Offset="1" Color="#397ab0" />
</LinearGradientBrush>
</Border.Background>
</Border>
<ContentPresenter HorizontalAlignment="Center" VerticalAlignment="Center"/>
</Grid>
</ControlTemplate>
</Setter.Value>
</Setter>
</Trigger>
</Style.Triggers>
</Style>
Is there any better way to do this? I've scenarios where my control template is having more lines of code, and I'd only require to change a single style like BorderBrush or something. How can I change control template from Style.Triggers efficiently?
If your intention is just to give a different Background to the Border. You can achieve this in the ControlTemplate.Triggers
<Style x:Key="Button" BasedOn="{StaticResource LoginButton}" TargetType="Button">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate >
<Grid>
<Border x:Name="brd" CornerRadius="4">
<Border.Background>
<LinearGradientBrush EndPoint="0,1">
<GradientStop Offset="0" Color="#0863a5" />
<GradientStop Offset="1" Color="#00457d" />
</LinearGradientBrush>
</Border.Background>
</Border>
<ContentPresenter HorizontalAlignment="Center" VerticalAlignment="Center"/>
</Grid>
<ControlTemplate.Triggers>
<Trigger Property="IsEnabled" Value="false">
<Setter Property="Background" TargetName="brd">
<Setter.Value>
<LinearGradientBrush EndPoint="0,1">
<GradientStop Offset="0" Color="#508fbd" />
<GradientStop Offset="1" Color="#397ab0" />
</LinearGradientBrush>
</Setter.Value>
</Setter>
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>