Importing Custom Wpf Control Library DLL - wpf

Question

i made a WpfControlLibrary DLL to make a custom ProgressBar to import in a WindowsForm Project. The problem is, compiling and everything works fine.
But when i try to import my dll by doing
ToolBox->Right Click->Choose Elements...->WPF Components->Browse...->Choose dll->ok
it returns this error
'...pathofthedll...' Doesn't contain any components that could be insert in your toolbox.
Here's the code of the WpfControlLibrary
<ProgressBar xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
x:Class="NewProgressBar"
x:Name="ProgressBar"
Margin="20"
Value="{Binding ElementName=progress, Path=Value}" Height="30" IsIndeterminate="False" Foreground="{DynamicResource BrushRed}" Width="300">
<ProgressBar.Resources>
<SolidColorBrush x:Key="BrushRed" Color="#FFD30101"/>
<SolidColorBrush x:Key="BrushGreen" Color="#FF27D301"/>
<SolidColorBrush x:Key="BrushYellow" Color="#FFD3D301"/>
</ProgressBar.Resources>
Public Class NewProgressBar
Inherits ProgressBar
Private mColor1 As SolidColorBrush
Private mColor2 As SolidColorBrush
Private mColor3 As SolidColorBrush
Private mMaxValue As Integer = 100
Private mCurrentValue As Double = 0
Public Sub New(ByVal color1 As String, ByVal color2 As String, ByVal color3 As String)
InitializeComponent()
Dim Brush1 As New SolidColorBrush
Brush1.Color = ConvertToRbg(color1)
Me.mColor1 = Brush1
Dim Brush2 As New SolidColorBrush
Brush2.Color = ConvertToRbg(color2)
Me.mColor2 = Brush2
Dim Brush3 As New SolidColorBrush
Brush3.Color = ConvertToRbg(color3)
Me.mColor3 = Brush3
Me.Resources.Add("BrushRed", Brush1)
Me.Resources.Add("BrushYellow", Brush2)
Me.Resources.Add("BrushGreen", Brush3)
End Sub
Public Property GetColor1() As String
Get
Return mColor1.Color.ToString
End Get
Set(value As String)
Dim Brush As New SolidColorBrush
Brush.Color = ConvertToRbg(value)
Me.mColor1 = Brush
End Set
End Property
Public Property GetColor2() As String
Get
Return mColor2.Color.ToString
End Get
Set(value As String)
Dim Brush As New SolidColorBrush
Brush.Color = ConvertToRbg(value)
Me.mColor2 = Brush
End Set
End Property
Public Property GetColor3() As String
Get
Return mColor3.Color.ToString
End Get
Set(value As String)
Dim Brush As New SolidColorBrush
Brush.Color = ConvertToRbg(value)
Me.mColor3 = Brush
End Set
End Property
Public Property GetMaxValue() As Integer
Get
Return mMaxValue
End Get
Set(value As Integer)
mMaxValue = value
End Set
End Property
Private Function ConvertToRbg(ByVal HexColor As String) As Color
Dim Red As String
Dim Green As String
Dim Blue As String
HexColor = Replace(HexColor, "#", "")
Red = Val("&H" & Mid(HexColor, 1, 2))
Green = Val("&H" & Mid(HexColor, 3, 2))
Blue = Val("&H" & Mid(HexColor, 5, 2))
Return Color.FromRgb(Red, Green, Blue)
End Function
Public Sub ChangeColor()
Dim prgrss As Double = mCurrentValue / 100
Dim redbrsh As SolidColorBrush = Me.Resources("BrushRed")
Dim grnbrsh As SolidColorBrush = Me.Resources("BrushGreen")
Dim ylwbrsh As SolidColorBrush = Me.Resources("BrushYellow")
If prgrss = 1D Then
Me.Foreground = grnbrsh
ElseIf prgrss >= 0.95D And prgrss < 1D Then
Me.Foreground = ylwbrsh
Else
Me.Foreground = redbrsh
End If
Dim number As Integer = prgrss
End Sub
Public Sub ChangeValue(ByVal value As Integer)
Me.Value = (100 * value) / mMaxValue
mCurrentValue = Me.Value
End Sub
End Class