Silverlight LinearGradientBrush in VB.NET

This article demonstrates how to use a linear gradient brush in Silverlight using XAML and VB.NET.
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This article demonstrates how to use a linear gradient brush in Silverlight using XAML and VB.NET.

Linear Gradient Brush

A linear gradient brush paints an area with a linear gradient. The LinearGradientBrush object represents a linear gradient brush. The default value linear gradient value is diagonal. The StartPoint and EndPoint properties of the LinearGradientBrush represent the start and end points of a gradient. The default values of these properties is (0, 0) and (1, 1), which is upper-left corner to lower-right corner of an area.

Figure 1 taken from MSDN shows a rectangle filled with a diagonal gradient and Figure 2 shows a rectangle filled with a gradient brush with multiple gradient stops. 
 

1.JPG

Figure 1

2.JPG
 

Figure 2

Creating a Linear Gradient Brush

The LinearGradientBrush element in XAML creates a linear gradient brush. The following code snippet creates a linear gradient brush with blue and red colors by setting GradientStops. The StartPoint and EndPoint values are (0, 0) and (1, 1).

<LinearGradientBrush StartPoint="0,0" EndPoint="1,1" >                   

    <GradientStop Color="Blue" Offset="0" />

    <GradientStop Color="Red" Offset="1.0" />                 

</LinearGradientBrush>

We can fill a shape with a gradient brush by setting a shape's Fill property to the gradient brush. The code snippet in Listing 1 creates a rectangle shape sets the Fill property to a LinearGradientBrush with blue and red colors.

<Rectangle Width="200" Height="100">

    <Rectangle.Fill>

        <LinearGradientBrush StartPoint="0,0" EndPoint="1,1" >                   

            <GradientStop Color="Blue" Offset="0" />

            <GradientStop Color="Red" Offset="1.0" />                 

        </LinearGradientBrush>

    </Rectangle.Fill>

</Rectangle>

Listing 1

The output looks like Figure 3.

3.JPG

Figure 3

Now let's apply multiple stops with multiple colors. The code snippet in Listing 2 creates a linear gradient brush with five stops.

<Rectangle Width="200" Height="100">

    <Rectangle.Fill>

        <LinearGradientBrush StartPoint="0,0" EndPoint="1,1" >                   

            <GradientStop Color="Blue" Offset="0.1" />

            <GradientStop Color="Orange" Offset="0.25" />

            <GradientStop Color="Yellow" Offset="0.50" />

            <GradientStop Color="Green" Offset="0.75" />

            <GradientStop Color="Red" Offset="1.0" />   

        </LinearGradientBrush>

    </Rectangle.Fill>

</Rectangle>

Listing 2

The new output generated by Listing 2 looks like Figure 4.

4.JPG

Figure 4

The CreateARectangleWithLGBrush method listed in Listing 3 draws same rectangle in Figure 4 dynamically.

    Public Sub CreateARectangleWithLGBrush()
        ' Create a Rectangle 
        Dim blueRectangle As New Rectangle()
        blueRectangle.Height = 100
        blueRectangle.Width = 200

        ' Create a linear gradient brush with five stops  
        Dim fiveColorLGB As New LinearGradientBrush()
        fiveColorLGB.StartPoint = New Point(0, 0)
        fiveColorLGB.EndPoint = New Point(1, 1)

        ' Create and add Gradient stops 
        Dim blueGS As New GradientStop()
        blueGS.Color = Colors.Blue
        blueGS.Offset = 0.0R
        fiveColorLGB.GradientStops.Add(blueGS)

        Dim orangeGS As New GradientStop()
        orangeGS.Color = Colors.Orange
        orangeGS.Offset = 0.25
        fiveColorLGB.GradientStops.Add(orangeGS)

        Dim yellowGS As New GradientStop()
        yellowGS.Color = Colors.Yellow
        yellowGS.Offset = 0.5R
        fiveColorLGB.GradientStops.Add(yellowGS)

        Dim greenGS As New GradientStop()
        greenGS.Color = Colors.Green
        greenGS.Offset = 0.75
        fiveColorLGB.GradientStops.Add(greenGS)

        Dim redGS As New GradientStop()
        redGS.Color = Colors.Red
        redGS.Offset = 1.0R
        fiveColorLGB.GradientStops.Add(redGS)

        ' Set Fill property of rectangle 
        blueRectangle.Fill = fiveColorLGB

        ' Add Rectangle to the page 
        LayoutRoot.Children.Add(blueRectangle)
    End Sub

Listing 3

By simply changing the StartPoint and EndPoint values, we can generate a vertical gradient shapes. By changing a few lines below in code listed in Listing 4 generates Figure 5.

        ' Create a linear gradient brush with five stops  
        Dim fiveColorLGB As New LinearGradientBrush()
        fiveColorLGB.StartPoint = New Point(0, 0.5)
        fiveColorLGB.EndPoint = New Point(1, 0.5)
 

Listing 4

5.JPG

Figure 5

Summary

In this article, we saw how to create and use a linear gradient brush in Silverlight using XAML and VB.NET.

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