Getting right mouse position

Hello,

First thanks for every help I get. I am new in DirectX and SlimDx. This is why I first developed a test application. Later I want to develop a 2D game. Now to my Problem. I want to get the mouse position in the 3D space. But I have problems with the calculation of the point.

#region fours try

float m_iClientSizeW = _control.Device.Viewport.Width;
float m_iClientSizeH = _control.Device.Viewport.Height;

Matrix worldview = _control.Device.GetTransform(Dx9.TransformState.View);
Matrix worldviewprojection = Matrix.Multiply(worldview, _control.Device.GetTransform(Dx9.TransformState.Projection));

Dx9.Viewport vp = _control.Device.Viewport;

// Unproject near plane
Vector3 vNear = new Vector3((float)posPoint.X, (float)posPoint.Y, 0);
Vector3 vFar = new Vector3((float)posPoint.X, (float)posPoint.Y, 1);

Vector3 vNearW = Vector3.Unproject(vNear,
            0, 0,
            m_iClientSizeW, m_iClientSizeH,
            0, 1, Matrix.Identity * worldviewprojection);

Vector3 vFarW = Vector3.Unproject(vFar,
            0, 0,
            m_iClientSizeW, m_iClientSizeH,
            0, 1, Matrix.Identity * worldviewprojection);

Ray ray = new Ray(vNearW, vFarW - vNearW);
#endregion

Here you can find my source code: https://github.com/ascholz/SlimDxTest

I have rode this article, http://www.vb6.us/tutorials/using-mouse-click-3d-space-directx-8 . But I have problems defining the plane for the z equals zero.

I hope someone can help me.

Best Regards

ascholz