Thank you.

Yes I am using 11.1

I commented out all my other code but i did not work. Your application did work.

but then I find the reason why it isn't working:

im my XAML Code i have the following in the <ig:XamMap>

           <ig:XamMap.Layers>
                <ig:MapLayer x:Name="mapLayer" FillMode="RandomInterpolate" Brushes="red orange blue">
                </ig:MapLayer>

            </ig:XamMap.Layers>

Without these lines of code it is working properly. I did not think that this would have an effect on zooming.

Is this normal, or should it wotk nevertheless?

if I add tjhe following to your sample code, it does also not work correctly:

<ig:XamMap.Layers>
                <ig:MapLayer >
                </ig:MapLayer>
 </ig:XamMap.Layers>

EDIT:

it does even not work if i left this piece of code out and add layers programaticlly with:

      Dim roadLayer As New MapLayer()
        roadLayer.LayerName = "roadLayer"
        roadLayer.StrokeThickness = 2
        reader = New ShapeFileReader()
        reader.Uri = "/../../Shapefiles/rivers"
        converter = New DataMapping.Converter()
        reader.DataMapping = TryCast(converter.ConvertFromString("Caption=NAME; ToolTip=NAME"), DataMapping)
        roadLayer.Reader = reader
        theMap.Layers.Add(roadLayer)

Thanks for your help!

I found nothing that could effect it.

that is my Initcoordinates method, which is called when the window is loaded, maybe there could be a fault?:

  Private Sub InitMapCoordinates()
        ' Convert define world dimensions
        Dim worldTopLeft As Point = New Point(-180, 90)
        Dim worldBottomRight As Point = New Point(180, -90)
        ' Convert Geodetic to Cartesian coordinates
        Dim winTopLeft As Point = Me.theMap.MapProjection.ProjectToMap(worldTopLeft)
        Dim winBottomRight As Point = Me.theMap.MapProjection.ProjectToMap(worldBottomRight)
        ' Create Rect structure the map control's WindowRect and WorldRect
        Dim winRect As New Rect()
        winRect.X = Math.Min(winTopLeft.X, winBottomRight.X)
        winRect.Y = Math.Min(winTopLeft.Y, winBottomRight.Y)
        winRect.Width = Math.Abs(winTopLeft.X - winBottomRight.X)
        winRect.Height = Math.Abs(winTopLeft.Y - winBottomRight.Y)
        Me.theMap.IsAutoWorldRect = False
        ' Change the map control's WindowRect and WorldRect
        Me.theMap.WorldRect = winRect
        Me.theMap.WindowRect = winRect
    End Sub