您需要给予您的ModelVisual3D命名，MeshGeometry3D没有Transform属性，其中模型有Transform属性。您还需要访问您的AxisAngleRotation3D对象以设置Angle属性。

<ModelVisual3D x:Name="MyModel">
....

编辑为CodeBehind方法添加了更多代码

public partial class MainWindow : Window
{
    AxisAngleRotation3D ax3d;
    public MainWindow()
    {
        InitializeComponent();

        ax3d = new AxisAngleRotation3D(new Vector3D(0, 2, 0), 1);
        RotateTransform3D myRotateTransform = new RotateTransform3D(ax3d);
        MyModel.Transform = myRotateTransform;
    }

    private void button1_Click(object sender, RoutedEventArgs e)
    {
        ax3d.Angle += 1 ;
    }
}

尽管在这种情况下，我认为最好在Xaml中实现转换。

<Window x:Class="WpfApplication1.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="MainWindow" Height="350" Width="525">
    <Grid>
        <Viewport3D Name="viewport3D1">
            <Viewport3D.Camera>
                <PerspectiveCamera x:Name="camMain" Position="6 5 4" LookDirection="-6 -5 -4">
                </PerspectiveCamera>
            </Viewport3D.Camera>
            <ModelVisual3D>
                <ModelVisual3D.Content>
                    <DirectionalLight x:Name="dirLightMain" Direction="-1,-1,-1">
                    </DirectionalLight>
                </ModelVisual3D.Content>
            </ModelVisual3D>
            <ModelVisual3D x:Name="MyModel">
                <ModelVisual3D.Content>
                    <GeometryModel3D>
                        <GeometryModel3D.Geometry>
                            <MeshGeometry3D x:Name="meshMain" 
                                Positions="0 0 0  1 0 0  0 1 0  1 1 0  0 0 1  1 0 1  0 1 1  1 1 1" 
                                TriangleIndices="2 3 1  2 1 0  7 1 3  7 5 1  6 5 7  6 4 5  6 2 0  2 0 4  2 7 3  2 6 7  0 1 5  0 5 4">
                            </MeshGeometry3D>
                        </GeometryModel3D.Geometry>
                        <GeometryModel3D.Material>
                            <DiffuseMaterial x:Name="matDiffuseMain">
                                <DiffuseMaterial.Brush>
                                    <SolidColorBrush Color="Red"/>
                                </DiffuseMaterial.Brush>
                            </DiffuseMaterial>
                        </GeometryModel3D.Material>
                    </GeometryModel3D>
                </ModelVisual3D.Content>
                <ModelVisual3D.Transform>
                    <RotateTransform3D>
                        <RotateTransform3D.Rotation>
                            <AxisAngleRotation3D x:Name="rotate" Axis="0 2 0"/>
                        </RotateTransform3D.Rotation>
                    </RotateTransform3D>
                </ModelVisual3D.Transform>
            </ModelVisual3D>
        </Viewport3D>
        <Slider Height="23" HorizontalAlignment="Left" 
                Margin="12,12,0,0" Name="slider1"
                VerticalAlignment="Top" Width="187" 
                Maximum="360"
                Value="{Binding ElementName=rotate, Path=Angle}" />

    </Grid>
</Window>

同样在本示例中，您可以通过设置其Angle属性来更改CodeBehind中的AxisAngleRotation3D：

rotate.Angle +=1;